Co-reporter:Zhiwen Zhao, Jie Qin, Chen Zhang, Yaorong Wang, Dan Yuan, and Yingming Yao
Inorganic Chemistry April 17, 2017 Volume 56(Issue 8) pp:4568-4568
Publication Date(Web):March 27, 2017
DOI:10.1021/acs.inorgchem.7b00107
Ionic rare-earth metal complexes 1–4 bearing an imidazolium cation were synthesized, which, as single-component catalysts, showed good activity in catalyzing cyclic carbonate synthesis from epoxides and CO2. In the presence of 0.2 mol % catalyst, monosubstituted epoxides bearing different functional groups were converted into cyclic carbonates in 60–97% yields under atmospheric pressure. In addition, bulky/internal epoxides with low reactivity yielded cyclic carbonates in 40–95% yields. More importantly, the readily available samarium complex 2 was reused for six successive cycles without any significant loss in its catalytic activity. This is the first recyclable rare-earth metal-based catalyst in cyclic carbonate synthesis.
Co-reporter:Hao Ouyang;Kun Nie;Dan Yuan;Yingming Yao
Dalton Transactions 2017 vol. 46(Issue 45) pp:15928-15938
Publication Date(Web):2017/11/21
DOI:10.1039/C7DT03001K
A series of rare-earth metal complexes stabilized by different amine bridged bis(phenolate) ligands were synthesized and well characterized. Their catalytic performances for the ring-opening polymerization of L-lactic acid O-carboxyanhydride (L-lacOCA) and L-lactide were explored. Sequential reactions of amine bridged bis(phenol) with (C5H5)3RE(THF) in a 1 : 1 molar ratio, followed by 1 equivalent of p-cresol gave the amine bridged bis(phenolate) rare-earth metal aryloxides {La[NNOO-R](OC6H4-4-CH3)(THF)}2 {[NNOO-R] = Me2NCH2CH2N}{CH2-(2-O-C6H2-R2-3,5)}2, R = Me (1), La[NNOO-R](OC6H4-4-CH3)(THF)2 [R = tBu (2); R = Cumyl (3)], Y[NNOO-R](OC6H4-4-CH3)(THF) [R = tBu (4)] and {Y[THFONOO-tBu](OC6H4-4-CH3)}2 {THFONOO-tBu = (CH2)3OCHCH2N[CH2-(2-O-C6H2-3,5-tBu2)]2} (5) in good isolated yields. Single-crystal structure determination revealed that complexes 1 and 5 have dimeric structures, whereas complexes 2 and 3 have monomeric structures in the solid state. It was found that these complexes are efficient initiators for the ring-opening polymerization of L-lacOCA, and the overall coordination environments around the metal centers and the ionic radii of the metal centers have an obvious influence on the catalytic performance. A comparative study on the polymerization kinetics of L-lacOCA and L-lactide initiated by complex 5 was carried out for the first time. The results obtained demonstrated that the polymerization of L-lacOCA and L-lactide is first order for the catalyst and monomer concentration in dichloromethane, respectively, and the Gibbs energy of activation of L-lacOCA and L-lactide is found to be essentially the same. Mechanistic studies revealed that L-lacOCA polymerization initiated by these rare-earth metal complexes proceeded via a coordination–insertion mechanism.
Co-reporter:Ya Xu;Dan Yuan;Yaorong Wang;Yingming Yao
Dalton Transactions 2017 vol. 46(Issue 18) pp:5848-5855
Publication Date(Web):2017/05/09
DOI:10.1039/C7DT00789B
Different aluminum complexes were synthesized by the reaction of aluminum alkyls with a hexadentate salen-type Schiff base. The reaction of N,N′-bis(3,5-di-tert-butylsalicylidene)-2,2′-(ethylenedioxy)dianiline (LH2) with one equiv. of AlMe3 in toluene at 100 °C proceeded by methane elimination to produce the intermediate methyl complex [AlMeL] (1), and then subsequent intramolecular methyl migration to give the aluminum complex [AlL′] (2) [L′ = (2-O-3,5-tBu2C6H2)CHNC6H4OCH2CH2OC6H4NCH(Me)(2′-O-3′,5′-tBu2C6H2)]. The reaction of the same ligand with AlEt3 under the same experimental conditions involved ethane elimination, ethylene elimination and intramolecular hydrogen migration, and led to the complex [AlL′′] (3) [L′′ = (2-O-3,5-tBu2C6H2)CHNC6H4OCH2CH2OC6H4NCH2(2′-O-3′,5′-tBu2C6H2)]. However, the interaction of two equivalents of AlMe3 and AlEt3 afforded the corresponding binuclear complexes [(AlMe2)2L] (4) and [(AlEt2)2L] (5), respectively, and no methyl or hydrogen migration was found. The solid-state structures of aluminum complexes 1–3 were determined by single-crystal X-ray diffraction. It was found that complexes 2–5 show a very effective catalytic activity for the cycloaddition of epoxides and CO2 in the presence of NBu4Br as a cocatalyst at atmospheric pressure.
Co-reporter:Chao Gong;Hao Ding;Chengrong Lu;Bei Zhao;Yingming Yao
Dalton Transactions 2017 vol. 46(Issue 18) pp:6031-6038
Publication Date(Web):2017/05/09
DOI:10.1039/C7DT00871F
A divalent ytterbium amidate 1 ([Yb3L6]·2C7H8 for short) was synthesized via amine-elimination of Yb[N(SiMe3)2]2(TMEDA) with an amide proligand N-2,6-diisopropylphenylbenzamide HL (L = 2,6-iPr2C6H3NC(O)Ph) and structurally characterized to be a trinuclear symmetric cluster. Further studies on the reduction of iPrNCNiPr by complex 1 provide Yb(III) complex 2 in hexane–THF ([(YbL2)2(μ-NiPrCNiPr)][YbL3(THF)]·C7H8), which is composed of two subunits in a unit cell, one is a bridged Yb(III) carbene, just the same as complex 4 ([(YbL2)2(μ-NiPrCNiPr)]·3C7H8) obtained in the same reaction in toluene, and the other is a homoleptic monomeric Yb(III) amidate (YbL3). It is also found that complex 2 decomposed to complex 3 ([YbL3]2·2C7H8) and 4 at 90 °C in toluene. Complexes 1–4 were confirmed by X-ray structure determination. Furthermore, complex 4 was proved to be a more active species than its precursor 1 in the catalytic addition of amines to carbodiimides. Finally, complex 1 was found to be an excellent pre-catalyst for the guanylation reaction with a wide scope of substrates.
Co-reporter:Chen Zhang, Weikai Gu, Yaorong Wang, Yingming Yao
Polyhedron 2017 Volume 134(Volume 134) pp:
Publication Date(Web):25 September 2017
DOI:10.1016/j.poly.2017.06.006
Four rare-earth metal complexes supported by Salpn ligand were synthesized, and their catalytic behaviors for the polymerization of rac-lactide (rac-LA) were explored. The amine elimination reactions of Salpn ligand LH2 (LH2 = (CH2)3[N = CH(C6H4-2-OH)]2) with RE[N(SiMe3)2]3 (RE = Y, Yb, Sm, Nd) in a 1:1 M ratio, and then with 1 equiv. of phenol ArOH (ArO = 2,6-But2-4-MeC6H2O) in THF gave the trinuclear rare-earth metal aryloxo complexes [LRE(OAr)(HMPA)]3 (RE = Y (1), Yb (2), Sm (3)), and the mononuclear neodymium complex LNd(OAr)(HMPA)2 (4), respectively, in good yields in the presence of HMPA (HMPA = hexamethylphosphoric triamide). Complexes 1 and 2 can also be prepared by the phenol elimination reactions of (ArO)3RE(THF) with LH2 in a 1:1 M ratio or salt metathesis reaction of LLi2(THF)x with anhydrous RECl3, then with NaOAr in THF. Complexes 1–4 were well characterized by elemental analyses and IR, as well as NMR spectroscopy in the case of complex 1. The definitive molecular structures of complexes 1–4 were determined by single-crystal X-ray analysis. The catalytic behaviors of these complexes for rac-LA polymerization were investigated. It was found that complexes 1–4 can initiate efficiently this polymerization and gave hetero-rich PLA. Kinetics study demonstrated that rac-LA polymerization initiated by complexes 1–3 has a first order relationship between polymerization rate and monomer concentration. A comparative kinetics study in THF and CHCl3 revealed that polymerization media have significant influence on the activity order of complexes 1–3 for rac-LA polymerization. The observed activity-increasing order of these complexes in THF is in agreement with the increasing order of their ionic radii, whereas it is in reverse order in CHCl3. A mechanism study demonstrated that the polymerization proceeded via a coordination-insertion mechanism, and the aryloxo group in these complexes acted as the initiating group.The trinuclear rare-earth metal aryloxo complexes [LRE(OAr)(HMPA)]3 (RE = Y (1), Yb (2), Sm (3)), and the mononuclear neodymium complex LNd(OAr)(HMPA)2 (4) supported by Salen ligand were synthesized, and their catalytic behaviors for the polymerization of rac-lactide (rac-LA) were explored.Download high-res image (54KB)Download full-size image
Co-reporter:Qiaolang Xia, Yu Cui, Dan Yuan, Yaorong Wang, Yingming Yao
Journal of Organometallic Chemistry 2017 Volume 846(Volume 846) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.jorganchem.2017.06.002
•Synthesis of six new lanthanide complexes stabilized by N-aryl substituted β-ketoiminato ligands.•Lanthanide amides and aryloxides can efficiently initiate the ring-opening polymerization of rac-LA.•The increasing order of activity of Y < Sm < Nd is in agreement with the order of their ionic radii.Several lanthanide complexes supported by N-aryl substituted β-ketoiminato ligands were synthesized by the protonolysis reaction. Reactions of 1-phenyl-3-N-(p-methoxyphenylimino)-1-butanone (HL) with Ln[N(SiMe3)2]3 and Ln(OAr)3(THF) (ArO = 2,6-But2-4-MeC6H2O) in a 2:1 M ratio gave mononuclear lanthanide amides L2Ln[N(SiMe3)2] [Ln = Y (1), Sm (2), Nd (3)] and aryloxides L2Ln(OAr) [Ln = Y (4), Nd (5)], respectively, whereas the same reaction with Yb[N(SiMe3)2]3 afforded an unexpected homoleptic ytterbium complex L3Yb (6). The solid-state structures of lanthanide complexes 1–6 were determined by single-crystal X-ray diffraction. It was found that complexes 1–5 can efficiently initiate the ring-opening of rac-lactide in THF to afford hetereotactic-rich polylactides.Download high-res image (156KB)Download full-size image
Co-reporter:Zenghui Fei;Chao Zeng;Chengrong Lu;Bei Zhao;Yingming Yao
RSC Advances (2011-Present) 2017 vol. 7(Issue 31) pp:19306-19311
Publication Date(Web):2017/03/28
DOI:10.1039/C7RA00468K
An asymmetric hydrophosphonylation reaction of diethyl phosphite with α,β-unsaturated amides catalyzed by [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 (RE = Sc (1), Y (2), La (3), Yb (4) and Lu (5)) with H2Ln ((S)-2,4-R2-6-[[2-(hydroxydiphenylmethyl)pyrrolidin-1-yl]methyl]phenol) (R = tBu (H2L1); R = 1-cumyl (H2L2) and R = 1-adm (H2L3)) was disclosed. The effects of different central metals and proligands on the addition reaction were tested and it was found that the combination of Sc complex 1 and ligand H2L2 gave the best results. An excellent chemical yield (up to 99%) and good to high enantioselectivities (varied from 73 to 89%) were achieved with a relatively broad scope of the unsaturated amides. The active species in the current system was also discussed.
Co-reporter:Jie Qin, Bin Xu, Yong Zhang, Dan Yuan and Yingming Yao
Green Chemistry 2016 vol. 18(Issue 15) pp:4270-4275
Publication Date(Web):03 May 2016
DOI:10.1039/C6GC00511J
Novel rare earth metal–zinc heterotrinuclear complexes have been synthesized, which showed high efficiency and selectivity in initiating the copolymerization of CO2 and cyclohexene oxide under mild conditions. Significant cooperation between rare earth metal and zinc centres that account for the good performance is observed. Copolymers of high polycarbonate content (up to 99%) as well as high molecular weight (up to 295800 g mol−1) were obtained at 25 °C under 0.7 MPa pressure of CO2.
Co-reporter:Wenyi Li, Hao Ouyang, Lijuan Chen, Dan Yuan, Yong Zhang, and Yingming Yao
Inorganic Chemistry 2016 Volume 55(Issue 13) pp:6520
Publication Date(Web):June 20, 2016
DOI:10.1021/acs.inorgchem.6b00639
Dinuclear aluminum methyl complexes stabilized by piperidyl–phenolato ligands were prepared and characterized. The ring-opening polymerizations of cyclohexene oxide (CHO) and propylene oxide (PO) initiated by dinuclear complexes and mononuclear analogues were investigated and compared. Enhanced activity of dinuclear complexes compared to that of mononuclear analogues in both the ring-opening polymerization of CHO and PO proves the synergistic interaction of two Al centers in the former. End-group analysis of oligomers by MALDI-TOF mass spectrometry confirms the role of methyl groups as initiating groups. A bimetallic mechanism is proposed, in which the cooperation of two Al centers are involved in polymerization processes.
Co-reporter:Yu Zhang, Qiu Sun, Yaorong Wang, Dan Yuan, Yingming Yao and Qi Shen
RSC Advances 2016 vol. 6(Issue 13) pp:10541-10548
Publication Date(Web):18 Jan 2016
DOI:10.1039/C5RA23270H
Zirconium complexes stabilized by piperazidine- and imidazolidine-bridged bis(phenolato) ligands have been synthesized and characterized. Their activities in catalyzing intramolecular hydroamination reactions have been tested and compared, which reveals the significant role that the ancillary ligands play in influencing catalytic activities. Cationic species derived from zirconium dibenzyl complexes showed good activities in catalyzing intramolecular hydroamination reactions of both primary and secondary amines, and afforded the respective N-heterocycles in 85% to 99% yields. Moreover, this catalytic system also catalyzed sequential cyclization of primary aminodienes, and generated bicyclic tertiary amines in 94–99% yields.
Co-reporter:Kun Nie, Chengwei Liu, Yong Zhang, Yingming Yao
Journal of Organometallic Chemistry 2016 Volume 804() pp:59-65
Publication Date(Web):15 February 2016
DOI:10.1016/j.jorganchem.2015.12.033
•Five new bimetallic organo-rare-earth metal complexes were synthesized.•The structures were elucidated by X-ray crystallography.•These complexes showed high catalytic activity for hydrophosphonylation reaction under mild conditions.Some bimetallic rare earth bis(cyclopentadienyl) derivatives supported by bridged bis(guanidinate) ligands {(C5H5)2RE[(RN)2CN(CH2)2]}2 [R = iPr, RE = Yb(1), Er(2), Y(3); R = Cy, RE = Yb(4)] and {(CH3C5H4)2Sm[(iPrN)2CN(CH2)2]}2 (5) were prepared by the reaction of lithium guanidinate {Li[(RN)2CN(CH2)2]}2 (R = iPr, Cy) with (C5H5)2RECl (RE = Yb, Er, Y) or (CH3C5H4)2SmCl in a 1:2 M ratio in THF. Complexes 1–5 were confirmed by elemental analyses, IR spectra and NMR spectroscopy (for complex 3). The molecular structures of complexes 1–3 and 5 were provided by X-ray structure diffraction, which indicated that these complexes have similar dinuclear solid state structure. The rare-earth ion in these complexes is bonded to two η5-cyclopentadienyl rings and one chelating guanidinate ligand. It was found that these rare-earth metal complexes are efficient catalysts for the hydrophosphonylation of various aldehydes, to generate α-hydroxyphosphonates in high yields under mild reaction conditions.Some bimetallic rare earth bis(cyclopentadienyl) derivatives supported by bridged bis(guanidinate) ligands were prepared, which showed high activity for the hydrophosphonylation of aldehydes under mild reaction conditions, to generate α-hydroxyphosphonates.
Co-reporter:Yanfei Yu, Dan Yuan, Yaorong Wang, Yingming Yao
Journal of Organometallic Chemistry 2016 Volume 819() pp:37-45
Publication Date(Web):15 September 2016
DOI:10.1016/j.jorganchem.2016.06.020
•Synthesis of six new lanthanide complexes stabilized by a novel salen-type Schiff-base ligand.•All lanthanide alkoxide complexes can efficiently initiate the ring-opening polymerization (ROP) of L-LA and rac-LA.•The first-order kinetic dependence on both l-lactide concentration and initiator concentration was found.A series of neutral lanthanide alkoxide complexes stabilized by a new salen-type Schiff-base ligand were synthesized, and their catalytic behaviors for the ring-opening polymerization of lactide were explored. Amine elimination reactions of N-methyl-N′,N″-bis(3,5-di-tert-butylsalicylidene)-2,2′-diaminodiethylamine (LH2) with Ln[N(SiMe3)2]3 (Ln = Sm, Nd, La) in a 1:1 M ratio in THF, followed by reactions with 1 equiv of alcohols (tBuOH, EtOH and CH3OCH2CH2OH), produced lanthanide alkoxide complexes LLn(OtBu)(THF) (Ln = Sm (1), Nd (2), La (3)), [LSm(μ-OEt)]2 (4) and [LSm(μ-OCH2CH2OCH3)]2 (5), respectively, whereas the same reaction with Yb[N(SiMe3)2]3 gave an unexpected homoleptic complex L2Yb2(μ-L) (6). X-ray structural determination showed that complexes 1–3 have a THF-solvated monomeric structure, whereas complexes 4–6 have an unsolvated dimeric structure. All lanthanide alkoxide complexes can efficiently initiate the ring-opening polymerization (ROP) of L-LA and rac-LA. The polymerization kinetics of L-LA initiated by complex 1 has been studied in detail and the first-order kinetic dependence on both l-lactide concentration and initiator concentration was found. Furthermore, all complexes showed moderate stereoselectivity for rac-LA polymerization to afford heterotactic-rich polylactides.
Co-reporter:Qinqin Qian, Wenguo Zhu, Chengrong Lu, Bei Zhao, Yingming Yao
Tetrahedron: Asymmetry 2016 Volume 27(Issue 19) pp:911-917
Publication Date(Web):15 October 2016
DOI:10.1016/j.tetasy.2016.07.014
A simple, efficient catalytic asymmetric Michael addition of malonates to unsaturated ketones has been successfully developed. This process was promoted by rare earth metal complexes 1–4 bearing a chiral phenoxy functionalized prolinol ligand at room temperature [L1RE(L1H) (H2L1 = (S)-2,4-di-tert-butyl-6-((2-(hydroxydiphenylmethyl)pyrrolidin-1-yl)methyl)phenol, RE = Yb 1, Y 2, Sc 3 and L2Sc(L2H) 4 (H2L2 = (S)-2,4-di-dimethylbenzyl-6-((2-(hydroxydiphenylmethyl)-pyrrolidin-1-yl)methyl)phenol)]. Complex 3 was the best catalyst in the transformation and the products were obtained in up to 99% yield and with 90% ee. In addition, the molecular structures of the catalysts were well characterized, including X-ray determination of complex 3.A simple, efficient catalytic asymmetric Michael addition of malonates to unsaturated ketones has been successfully developed. This process was promoted by rare earth metal complexes 1–4, which is bearing chiral phenoxy functionalized prolinol ligand at room temperature. The Sc complex 3 performed the best and the products reached up to 99% yield and 90% ee.Diisopropyl 2-(3-oxo-1,3-diphenylpropyl)malonateC24H28O5[α]D20 = +18.9 (c 0.925, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)Diisopropyl 2-(3-(4-methoxyphenyl)-3-oxo-1-phenylpropyl)malonateC25H30O6[α]D20 = +17.8 (c 0.449, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)Diisopropyl 2-(1-phenyl-3-oxo-3-(4-chlorophenyl)propyl)malonateC24H27ClO5[α]D20 = +14.5 (c 0.932, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)Diisopropyl 2-(1-phenyl-3-oxo-3-(4-bromophenyl)propyl)malonateC24H27BrO5[α]D20 = +10.4 (c 0.869, CHCl3)Source of chirality: the synthesisAbsolute configuration: (2S)Diisopropyl 2-(1-phenyl-3-oxo-3-(4-trifluoromethylphenyl)propyl)malonateC25H27F3O5[α]D20 = +8.8 (c 0.963, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)Diisopropyl 2-(1-(4-methoxyphenyl)-3-oxo-3-phenylpropyl)malonateC25H30O6[α]D20 = +23.8 (c 0.126, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)Diisopropyl 2-(1-naphthyl-3-oxo-3-phenylpropyl)malonateC28H30O5[α]D20 = +23.6 (c 0.742, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)Diisopropyl 2-(1-(4-fluorophenyl)-3-oxo-3-phenylpropyl)malonateC24H27FO5[α]D20 = +22.0 (c 0.726, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)Diisopropyl 2-(1-(4-chlorophenyl)-3-oxo-3-phenylpropyl)malonateC24H27ClO5[α]D20 = +17.1 (c 0.703, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)Diisopropyl 2-(1-(4-nitrophenyl)-3-oxo-3-phenylpropyl)malonateC24H27NO7[α]D20 = +23.6 (c 0.826, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)Diisopropyl 2-(1-(2-chlorophenyl)-3-oxo-3-phenylpropyl)malonateC24H27ClO5[α]D20 = +29.1 (c 0.808, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)Diisopropyl 2-(1-(2-methoxyphenyl)-3-oxo-3-phenylpropyl)malonateC25H30O6[α]D20 = +18.3 (c 0.601, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)Diisopropyl 2-(3-(furan-2-yl)-3-oxo-1-phenylpropyl)malonateC22H26O6[α]D20 = +27.4 (c 0.821, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)Diisopropyl 2-(3-(thiophen-2-yl)-3-oxo-1-phenylpropyl)malonateC22H26O5S[α]D20 = +14.4 (c 0.766, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)2-(5-Isopropoxy-4-(isopropoxycarbonyl)-5-oxo-3-phenylpentanoyl)pyridine 1-oxideC23H27NO6[α]D20 = +13.2 (c 0.088, CHCl3)Source of chirality: synthesisAbsolute configuration: (3S)Diisopropyl 2-(2-benzoyl-3-oxo-1,3-diphenylpropyl)malonateC31H32O6[α]D20 = +11.2 (c 0.102, CHCl3)Source of chirality: synthesisAbsolute configuration: (2S)
Co-reporter:Pengfei Gao, Zhiwen Zhao, Lijuan Chen, Dan Yuan, and Yingming Yao
Organometallics 2016 Volume 35(Issue 11) pp:1707-1712
Publication Date(Web):May 4, 2016
DOI:10.1021/acs.organomet.6b00153
A series of dinuclear aluminum complexes 1–4 stabilized by amine-bridged poly(phenolato) ligands have been synthesized, which are highly active in catalyzing the cycloaddition of epoxides and CO2. In the presence of 0.3 mol % complex 3 and 0.9 mol % NBu4Br at 1 bar CO2 pressure, terminal epoxides bearing different functional groups were converted to cyclic carbonates in 60–97% yields. Complex 3 is one of the rare examples of Al-based catalysts capable of promoting the cycloaddition at 1 bar pressure of CO2. Moreover, reactions of more challenging disubstituted epoxides also proceeded at an elevated pressure of 10 bar and afforded cyclic carbonates in 52–90% yields.
Co-reporter:Qiu Sun, Yaorong Wang, Dan Yuan, Yingming Yao and Qi Shen
Chemical Communications 2015 vol. 51(Issue 36) pp:7633-7636
Publication Date(Web):27 Mar 2015
DOI:10.1039/C5CC01780G
An in situ generated cationic zirconium complex stabilized by an n-butylamine-bridged bis(phenolato) ligand has been developed to catalyse hydroamination reactions of secondary amines, which is the first example of group 4 metal based catalysts capable of mediating intermolecular hydroamination reactions of N-aryl/alkyl amines.
Co-reporter:Chao Zeng, Dan Yuan, Bei Zhao, and Yingming Yao
Organic Letters 2015 Volume 17(Issue 9) pp:2242-2245
Publication Date(Web):April 23, 2015
DOI:10.1021/acs.orglett.5b00833
A simple and efficient catalytic enantioselective epoxidation of α,β-unsaturated ketones has been successfully developed, which was catalyzed by rare-earth metal amides [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 (RE = Yb (1), La (2), Sm (3), Y (4), Lu (5)) in the presence of phenoxy-functionalized chiral prolinols at room temperature using tert-butylhydroperoxide (TBHP) as the oxidant. The combination of an Yb-based amide 1 and a chiral proligand (S)-2,4-di-tert-butyl-6-((2-(hydroxydiphenylmethyl)pyrrolidin-1-yl)methyl)phenol) performed very well, and both the yields and the enantiomeric excess of the chiral epoxides reached up to 99% and 99% ee.
Co-reporter:Yu Cui, Weikai Gu, Yaorong Wang, Bei Zhao, Yingming Yao and Qi Shen
Catalysis Science & Technology 2015 vol. 5(Issue 6) pp:3302-3312
Publication Date(Web):13 Apr 2015
DOI:10.1039/C5CY00322A
A series of neutral rare-earth metal aryloxides and amides supported by a new pentadentate (N2O3) salen ligand were synthesized, and their catalytic behaviors for the ring-opening polymerization of rac-lactide (rac-LA) were explored. The protolysis reactions of N,N′-bis(3,5-di-tert-butylsalicylidene)-2,2′-diaminodiphenyl ether (LH2) with (ArO)3Ln(THF) (ArO = 2,6-But2-4-MeC6H2O) and Ln[N(SiMe3)2]3 in a 1:1 molar ratio in THF gave the neutral rare-earth metal aryloxides LLn(OAr)(THF)n [n = 0, Ln = Sc (1), Yb (2); n = 1, Ln = Y (3), Sm (4) and Nd (5)] and rare-earth metal amides LLnN(SiMe3)2 [Ln = Yb (6), Y (7)], respectively. X-ray structural determination showed that complexes 1, 2, 6 and 7 have monomeric structures, in which the coordination geometry around the rare-earth metal atom can be best described as a distorted trigonal prism. Complexes 3 and 5 are THF-solvated monomers and each of the rare-earth metal atoms is seven-coordinated to form a distorted capped trigonal prism. It was found that all of these complexes can efficiently initiate the ring-opening polymerization (ROP) of rac-LA to give heterotactic-rich polylactides (PLAs). The highly heterotactic PLA (Pr up to 0.93) was obtained using complex 2 as the initiator at a polymerization temperature of 0 °C. The observed increasing order of activity of 1 < 2 < 3 < 4 ≈ 5 is in agreement with the order of their ionic radii, whereas the order of stereoselectivity is in the reverse order. The rare-earth metal salen amides can initiate rac-LA polymerization in a controlled manner, while polymerization using the rare-earth metal salen aryloxides is less controlled at room temperature.
Co-reporter:Lijuan Chen, Wenyi Li, Dan Yuan, Yong Zhang, Qi Shen, and Yingming Yao
Inorganic Chemistry 2015 Volume 54(Issue 10) pp:4699-4708
Publication Date(Web):April 28, 2015
DOI:10.1021/acs.inorgchem.5b00022
A series of mono- and dinuclear aluminum alkyl complexes stabilized by phenolato ligands have been prepared through alkane elimination reactions. Treatment of piperazidine-bridged bis(phenol)s C4H8N2[1,4-(2-OH-3,5-Me2-C6H2CH2)2] (H2[ONNO]1), C4H8N2[1,4-(2-OH-3-tBu-5-Me-C6H2CH2)2] (H2[ONNO]2), and C4H8N2[1,4-(2-OH-3,5-tBu2-C6H2CH2)2] (H2[ONNO]3) with 2.5–3 equiv of AlR3 (R = Me, Et) afforded dinuclear aluminum complexes (AlMe2)2[ONNO]1 (1), (AlMe2)2[ONNO]2 (2), (AlMe2)2[ONNO]3 (3), (AlEt2)2[ONNO]1 (4), (AlEt2)2[ONNO]2 (5), and (AlEt2)2[ONNO]3 (6), respectively. In order to compare the catalytic activities of these bimetallic complexes with their mononuclear counterparts, mono(phenolato) aluminum complexes AlMe2[ON]1 (7), AlMe2[ON]2 (8), AlMe2[ON]3 (9), AlEt2[ON]2 (10), and AlEt2[ON]3 (11) were synthesized from reactions of 1 equiv of AlMe3 or 2 equiv of AlEt3 with phenols that bear piperidine moieties, i.e., [2-(CH2NC5H10)-4,6-Me2-C6H2OH (H[NO]1), 2-(CH2NC5H10)-4-Me-6-tBu-C6H2OH (H[NO]2), and 2-(CH2NC5H10)-4,6-tBu2-C6H2OH (H[NO]3)], respectively. In comparison, reactions of H[NO]n (n = 2, 3) with 0.5 equiv of AlEt3 led to the isolation of mononuclear monoalkyl complexes AlEt[NO]22 (12) and AlEt[NO]32 (13), respectively. All complexes have been characterized by elemental analysis and NMR spectroscopy, and the solid state structures of 5 complexes have been determined by X-ray diffraction analysis. The activities of both binuclear and mononuclear aluminum complexes in initiating the ring-opening polymerization (ROP) of ε-caprolactone have also been investigated and compared. In general, these phenolato-Al complexes showed high activities in initiating the ROP in the absence of alcohols. More importantly, dinuclear complexes have been found to be 2–8 times more active than their mononuclear counterparts, which provides evidence for the cooperation between two metal centers in the former.
Co-reporter:Qiu Sun, Yaorong Wang, Dan Yuan, Yingming Yao and Qi Shen
Dalton Transactions 2015 vol. 44(Issue 47) pp:20352-20360
Publication Date(Web):01 Oct 2015
DOI:10.1039/C5DT02643A
A series of zirconium complexes bearing amine-bridged bis(phenolato) ligands of different steric and electronic properties have been synthesized, and their activities in catalyzing intermolecular hydroamination reactions have been studied and compared. In general, hexacoordinate zirconium dibenzyl complexes 1–4 stabilized by [ONNO]- or [ONOO]-type ligands were found to be less active than pentacoordinate complexes 5 and 7 that carry [ONO]-type ligands, which clearly imply that amine-bridged bis(phenolato) ligands play crucial roles in influencing catalytic activities. Complex 5 showed good activities and regioselectivities in catalysing reactions of various primary amines and alkynes. Moreover, reactions of challenging substrates, including secondary amines, internal alkynes, and hydrazines, were achieved with in situ generated cationic species from complex 5 and [Ph3C][B(C6F5)4].
Co-reporter:Chao Wang;Changpeng Chen;Jian Han;Jingyu Zhang;Yingming Yao;Yingsheng Zhao
European Journal of Organic Chemistry 2015 Volume 2015( Issue 13) pp:2972-2977
Publication Date(Web):
DOI:10.1002/ejoc.201500086
Abstract
A highly efficient and practical transition-metal-free CsOH/O2 catalyst system was developed for the N-alkylation of amines with alcohols under argon. This strategy was compatible with many alcohols and exhibits excellent functional group tolerance. More significantly, the selective formation of secondary amines was achieved in excellent yields. The detailed mechanistic study gave a clear understanding of the role of base and oxygen in the catalytic cycle.
Co-reporter:Hao Cheng, Yang Xiao, Chengrong Lu, Bei Zhao, Yaorong Wang and Yingming Yao
New Journal of Chemistry 2015 vol. 39(Issue 10) pp:7667-7671
Publication Date(Web):18 Jun 2015
DOI:10.1039/C5NJ00506J
Two new bis(amidate) lanthanide amides {LLn[N(SiMe3)2]·THF}2 (H2L = N,N′-(cyclohexane-1,2-diyl)-bis(4-tert-butylbenzamide); Ln = Sm(4), Yb(5)), which were prepared by the treatment of the bridged amide proligand H2L with Ln[N(SiMe3)2]3 in tetrahydrofuran, had been characterized by single-crystal X-ray diffraction and elemental analyses. Both complexes 4 and 5 and the three known isomorphs {LRE[N(SiMe3)2]·THF}2 (RE = La(1), Nd(2), Y(3)) were successfully employed in the addition of amines to carbodiimides for the first time and were found to be efficient catalysts in the transformation at 60 °C under solvent-free conditions. The Nd-based catalyst 2 showed the highest reactivity and provided various guanidines with good functional group tolerance in high to excellent yields.
Co-reporter:Tinghua Zeng, Qinqin Qian, Bei Zhao, Dan Yuan, Yingming Yao and Qi Shen
RSC Advances 2015 vol. 5(Issue 65) pp:53161-53171
Publication Date(Web):09 Jun 2015
DOI:10.1039/C5RA10151D
Eight rare-earth metal guanidinates supported by a versatile family of chelating amine-bridged bis(phenolate) ligands were synthesized. Metathesis reactions of rare-earth metal chlorides [LnClL1(THF)] stabilized by amine-bridged bis(phenolate) ligand L1 with in situ generated lithium guanidinates in a 1:1 molar ratio in THF afforded ytterbium guanidinates YbL1 [R2NC(NR1)2] [R1 = –iPr, R2N = –NiPr2 (1), –N(CH2)5 (2)]. Insertion reactions of the yttrium amides bearing bridged bis(phenolate) ligands with 1 equiv of N,N′-diisopropylcarbodiimide (DIC) yielded six yttrium guanidinates YL1 [(SiHMe2)2NC(NiPr)2] (3), YL2[(SiHMe2)2NC(NiPr)2](THF) (4), YL3[(SiHMe2)2NC(NiPr)2] (5), YL4[(SiHMe2)2NC(NiPr)2] (6), YL5 [(SiHMe2)2NC(NiPr)2] (7), YL6[(SiHMe2)2NC(NiPr)2] (8), respectively. The behaviors of complexes 1–8 in the polymerization of rac-lactide (LA) and rac-β-butyrolactone (BBL) were also explored. It was found that complexes 1–8 efficiently initiated the ring-opening polymerization (ROP) of rac-LA and rac-BBL in a controlled manner, providing highly heterotactic polylactide (Pr up to 0.99) and highly syndiotactic poly(3-hydroxybutyrate) (Pr up to 0.82). The framework of the bridge played a significant role in governing the stereoselectivity, while guanidinate groups work as initiating groups.
Co-reporter:Chao Wang, Lingling Huang, Min Lu, Bei Zhao, Yaorong Wang, Yong Zhang, Qi Shen and Yingming Yao
RSC Advances 2015 vol. 5(Issue 115) pp:94768-94775
Publication Date(Web):28 Oct 2015
DOI:10.1039/C5RA20285J
A series of anionic organo-rare-earth amido complexes stabilized by dianionic phenoxy-amido ligands were prepared and their catalytic behavior for amidation reactions of aldehydes with amines was elucidated. Amine elimination reaction of Ln[N(SiMe3)2]3(μ-Cl)Li(THF)3 with an equimolar of lithium aminophenoxy {[HNO]1Li(THF)}2, which was prepared by the reaction of [HNOH]1 {[HNOH]1 = N-p-fluoro-phenyl(2-hydroxy-3,5-di-tert-butyl)benzylamine} with one equivalent of n-BuLi in tetrahydrofuran (THF) in situ, gave the anionic phenoxy-amido rare earth amido complexes [NO]12Ln[N(SiMe3)2][Li(THF)]2 [Ln = Y (1), Yb (2), Sm (3), Nd (4)] in high isolated yields. Similar reactions of Ln[N(SiMe3)2]3(μ-Cl)Li(THF)3 with {[HNO]2Li(THF)}2, and {[HNO]3Li(THF)}2 in THF gave the anionic rare-earth amides [NO]22Ln[N(SiMe3)2][Li(THF)]2 [Ln = Sm (5), Nd (6)] and [NO]32Ln[N(SiMe3)2][Li(THF)]2 [Ln = Sm (7), Nd (8)] {[HNOH]2 = N-p-chloro-phenyl(2-hydroxy-3,5-di-tert-butyl)benzylamine; [HNOH]3 = N-p-bromo-phenyl(2-hydroxy-3,5-di-tert-butyl)benzylamine}, respectively. All of these complexes were fully characterized. X-ray structural determination revealed that these complexes are isostructural, and have solvated monomeric structures. Each of the rare-earth ions is coordinated by two phenoxy-amido ligands and one N(SiMe3)2 group, and the coordination geometry can be described as a distorted trigonal bipyramid. Each of the lithium atoms is surrounded by one aryloxo group, one amido group and one THF molecule, and the coordination geometry can be described as a trigonal plane. The catalytic behavior of these rare-earth amides for the amidation reaction of aldehyde with amine was elucidated. It was found that these complexes are efficient catalysts for this transformation to produce amides in good to excellent yields under mild reaction conditions, and in some cases, diacylamide compounds can be prepared conveniently.
Co-reporter:Xiao-De An, Hongyan Liu, Zhong-Liang Xu, Yi Jin, Xia Peng, Ying-Ming Yao, Meiyu Geng, Ya-Qiu Long
Bioorganic & Medicinal Chemistry Letters 2015 Volume 25(Issue 3) pp:708-716
Publication Date(Web):1 February 2015
DOI:10.1016/j.bmcl.2014.11.070
Starting from our previously identified novel c-Met kinase inhibitors bearing 1H-imidazo[4,5-h][1,6]naphthyridin-2(3H)-one scaffold, a global structural exploration was conducted to furnish an optimal binding motif for further development, directed by the enzyme inhibitory mechanism. First round SAR study picked two imidazonaphthyridinone frameworks with 1,8- and 3,5-disubstitution pattern as class I and class II c-Met kinase inhibitors, respectively. Further structural optimization on type II inhibitors by truncation of the imidazonaphthyridinone core and incorporation of an N-phenyl cyclopropane-1,1-dicarboxamide pharmacophore led to the discovery of novel imidazopyridine-based c-Met kinase inhibitors, displaying nanomolar enzyme inhibitory activity and improved Met kinase selectivity. More significantly, the new chemotype c-Met kinase inhibitors effectively inhibited Met phosphorylation and its downstream signaling as well as the proliferation of Met-dependent EBC-1 human lung cancer cells at submicromolar concentrations.A new class of imidazopyridine-based c-Met kinase inhibitors exhibited nanomolar inhibition against the enzyme and the growth of Met-driven EBC-1 human lung cancer cells.
Co-reporter:Tinghua Zeng, Qinqin Qian, Yaorong Wang, Yingming Yao, Qi Shen
Journal of Organometallic Chemistry 2015 Volume 779() pp:14-20
Publication Date(Web):1 March 2015
DOI:10.1016/j.jorganchem.2014.12.021
•Four ytterbium guanidinates bearing bridged bis(phenolate) ligand were prepared.•The solid state structures of all four complexes were determined by X-ray diffraction analysis.•Ytterbium guanidinates showed high activities in catalyzing hydrophosphonylation reactions of aldehydes.A series of ytterbium guanidinato complexes stabilized by an amine-bridged bis(phenolate) ligand were prepared, and their catalytic property for the hydrophosphonylation reaction of aldehydes was explored. Metathesis reactions of amine-bridged bis(phenolate) ytterbium chlorides LYbCl(THF) [L = Me2NCH2CH2N{CH2-(2-OC6H2tBu2-3,5)}2] with corresponding lithium guanidinates in a 1:1 molar ratio in THF gave the expected ytterbium guanidinato complexes LYb[R2NC(NR1)2] [R1 = Cy, R2N = N(TMS)2 (1), N(CH2)5 (2); R1 = iPr, R2N = N(TMS)2 (3), NPh2 (4)]. These ytterbium complexes were well characterized by elemental analyses, IR spectroscopy and single-crystal X-ray structure determination. The metal ion is six-coordinated by two oxygen and two nitrogen atoms from the bis(phenolate) ligand, and two nitrogen atoms from one guanidinato group. The coordination geometry around ytterbium can be described as a distorted octahedron. It was found that these ytterbium guanidinato complexes are highly efficient catalysts for the hydrophosphonylation reaction of various aldehydes under mild conditions.Four ytterbium guanidinato complexes stabilized by an amine-bridged bis(phenolate) ligand were prepared, which showed very high activity for the hydrophosphonylation of aldehydes with diethyl phosphite under mild reaction conditions.
Co-reporter:Kun Nie;Chengwei Liu;Yong Zhang;Yingming Yao
Science China Chemistry 2015 Volume 58( Issue 9) pp:1451-1460
Publication Date(Web):2015 September
DOI:10.1007/s11426-015-5407-9
A series of bimetallic lanthanide bis(amido) complexes stabilized by bridged bis(guanidinate) ligands {[(Me3Si)2N]2Ln[(RN)2-CN(CH2)2]}2 [R=iPr, Ln=Sm (1), Yb (2), Y (3); R=cyclohexyl (Cy), Ln=Sm (4), and Yb (5)] were synthesized through the metathesis reactions of {Ln(µ-Cl)[N(SiMe3)2]2(THF)}2 (Ln=Sm, Yb, Y) with lithium guanidinate {Li[(RN)2CN(CH2)2]}2 (R=iPr, Cy), the latter of which was generated in situ by the reaction of carbodiimides with lithium amides. Complexes 1–5 were well characterized by elemental analyses, IR spectra, and (for Complex 3) NMR spectroscopy. The solid-state molecular structures of all of the complexes were determined by single-crystal X-ray analyses with the exception of Complex 3, which showed similar unsolvated centrosymmetric dinuclear structures. Each of the lanthanide centers is four-coordinated with two nitrogen atoms from a guanidinate ligand and two nitrogen atoms from two amido groups. The piperazidine rings adopt chair conformations in all cases. These organolanthanide complexes were found to be efficient catalysts for the hydrophosphonylation reaction of various aldehydes and unactivated ketones and to afford α-hydroxyphosphonates in high yields under low catalyst loading (0.1 mol%) in a short reaction time.
Co-reporter:Weikai Gu, Pengfei Xu, Yaorong Wang, Yingming Yao, Dan Yuan, and Qi Shen
Organometallics 2015 Volume 34(Issue 12) pp:2907-2916
Publication Date(Web):June 9, 2015
DOI:10.1021/acs.organomet.5b00223
A series of yttrium and ytterbium complexes supported by Salen ligands with different steric and electronic properties were synthesized, and their catalytic performances for the polymerization of rac-lactide (rac-LA) were explored. The phenol elimination reactions of (ArO)3Ln(THF) (ArO = 2,6-But2-4-MeC6H2O) with a number of Salen ligands (CH3)2C[CH2N═CH(C6H2-2-OH-3,5-R2)]2 [L1H2, R = H; L2H2, R = Cl; L3H2, R = But; L4H2, R = CMe2Ph] and CH2[CH2N═CH(C6H2-2-OH-3,5-Cl2)]2 (L5H2), in a 1:1 molar ratio gave yttrium and ytterbium Salen aryloxides L1Ln(OAr)(THF)2 (Ln = Y (1), Yb (2)), L2Ln(OAr)(THF)n (Ln = Y (3), n = 2; Ln = Yb (4), n = 1), L3Y(OAr) (5), L4Y(OAr)(THF) (6), and L5Yb(OAr)(THF) (7), respectively. The amine elimination reactions of L3H2 with Y[N(SiMe3)2]3 in a 1:1 molar ratio and then with 1 equiv of phenol ArOH, and alcohols PhCH2OH and PriOH, produced complex 5 and the yttrium Salen alkoxides [L3Y(μ-OCH2Ph)]2 (8) and [L3Y(μ-OPri)]2 (9), respectively. X-ray structural determination showed that complexes 1–4 and 7 have a THF-solvated monomeric structure, and complex 5 has an unsolvated monomeric structure, whereas complex 8 has an unsolvated dimeric structure. All of these complexes can initiate the ring-opening polymerization of rac-LA at 30 °C in THF. It was found for the first time that the overall coordination environment around the metal center has an obvious influence on the stereoselectivity of these lanthanide Salen complexes. Five-coordinated complex 5 with bulky tert-butyl substituent groups on the phenyl rings displayed apparently lower stereoselectivity than seven-coordinated complex 1, although there is no substituent on the ortho-positions of the Salen ligand L1 in the latter. Complex 7 bearing Cl substituents on the Salen ligand showed the highest stereoselectivity among these lanthanide complexes for rac-LA polymerization, and heterotactic polylactides (Pr up to 0.88) can be obtained at 30 °C in THF.
Co-reporter:Jie Qin, Peng Wang, Qingyan Li, Yong Zhang, Dan Yuan and Yingming Yao
Chemical Communications 2014 vol. 50(Issue 75) pp:10952-10955
Publication Date(Web):31 Mar 2014
DOI:10.1039/C4CC02065K
Readily available lanthanide complexes stabilized by a bridged poly(phenolate) ligand have been used for the first time as efficient catalysts for the insertion of CO2 into epoxides to generate cyclic carbonates with high activity, high selectivity, and a wide substrate scope under mild conditions.
Co-reporter:Chengwei Liu, Yu Zhang, Qinqin Qian, Dan Yuan, and Yingming Yao
Organic Letters 2014 Volume 16(Issue 23) pp:6172-6175
Publication Date(Web):November 14, 2014
DOI:10.1021/ol5030713
It was found for the first time that organic alkali metal compounds serve as highly efficient precatalysts for the hydrophosphonylation reactions of aldehydes and unactivated ketones with dialkyl phosphite under mild conditions. For ketone substrates, a reversible reaction was observed, and the influence of catalyst loading and reaction temperature on the reaction equilibrium was studied in detail. Overall, the hydrophosphonylation reactions catalyzed by 0.1 mol % n-BuLi were completed within 5 min for a broad range of substrates and generated a series of α-hydroxy phosphonates in high yields.
Co-reporter:Qinqin Qian, Yufang Tan, Bei Zhao, Tao Feng, Qi Shen, and Yingming Yao
Organic Letters 2014 Volume 16(Issue 17) pp:4516-4519
Publication Date(Web):August 22, 2014
DOI:10.1021/ol5020398
Four novel heterobimetallic complexes [REL2]{[(THF)3Li]2(μ-Cl)} stabilized by chiral phenoxy-functionalized prolinolate (RE = Yb (1), Y (2), Sm (3), Nd (4), H2L = (S)-2,4-di-tert-butyl-6-[[2-(hydroxydiphenylmethyl)pyrrolidin-1-yl]methyl]phenol have been synthesized and characterized. These readily available complexes are highly active in catalyzing the epoxidation of α,β-unsaturated ketones, while the enantioselectivity varies according to the ionic radii of the rare earth center. A series of chalcone derivatives were converted to chiral epoxides in 80 → 99% ee at 0 °C using TBHP as the oxidant in the presence of 10 mol % of 1.
Co-reporter:Chengwei Liu, Qinqin Qian, Kun Nie, Yaorong Wang, Qi Shen, Dan Yuan and Yingming Yao
Dalton Transactions 2014 vol. 43(Issue 22) pp:8355-8362
Publication Date(Web):19 Mar 2014
DOI:10.1039/C4DT00522H
Lanthanide anilido complexes stabilized by the 2,6-diisopropylanilido ligand have been synthesized and characterized, and their catalytic activity for hydrophosphonylation reaction was explored. A reaction of anhydrous LnCl3 with 5 equivalents of LiNHPh-iPr2-2,6 in THF generated the heterobimetallic lanthanide–lithium anilido complexes (2,6-iPr2PhNH)5LnLi2(THF)2 [Ln = Sm(1), Nd(2), Y(3)] in good isolated yields. These complexes are well characterized by elemental analysis, IR, NMR (for complex 3) and single-crystal structure determination. Complexes 1–3 are isostructural. In these complexes, the lanthanide metal ion is five-coordinated by five nitrogen atoms from five 2,6-diisopropylanilido ligands to form a distorted trigonal bipyramidal geometry. The lithium ion is coordinated by two nitrogen atoms from two 2,6-diisopropylanilido ligands, and one oxygen atom from a THF molecule. It was found that these simple lanthanide anilido complexes are highly efficient for catalyzing hydrophosphonylation reactions of various aldehydes and unactivated ketones to generate α-hydroxyphosphonates in good to excellent yields (up to 99%) within a short time (5 min for aldehydes, 20 min for ketones). Furthermore, the mechanism of hydrophosphonylation reactions has also been elucidated via1H NMR monitoring of reaction.
Co-reporter:Hairong Zhou, Yinyin Jiang, Muzi Chen, Yaorong Wang, Yingming Yao, Bing Wu, Dongmei Cui
Journal of Organometallic Chemistry 2014 Volumes 763–764() pp:52-59
Publication Date(Web):1 August 2014
DOI:10.1016/j.jorganchem.2014.04.017
•Three new lanthanide amides bearing phenoxy(quinolinyl)amide ligand were prepared.•Lanthanide-lithium heterobimetallic complexes were prepared and characterized.•All the lanthanide amides can initiate the ring-opening polymerization of PDO.The amine elimination reaction of quinolinyl aminophenol (LH2) with Ln[N(SiMe3)2]3(μ-Cl)Li(THF)3 in THF afforded lanthanide-lithium aminophenoxy complexes L2LnLi(THF)2 (Ln = Yb (1), Sm (2)), while the similar reaction with Ln[N(SiMe3)2]3 in toluene gave normal monoamido lanthanide complexes LLnN(SiMe3)2(DME) (Ln = Sm (3), Nd (4), La (5)). All complexes have been fully characterized. X-ray structural determination revealed that complexes 1 and 2 have a monomeric C2-symmetric heterobimetallic structure, in which the lanthanide atom is connected to the lithium atom by two oxygen bridges from two phenoxy(quinolinyl)amide ligands. Complexes 4 and 5 have a solvated monomeric structure, and the lanthanide metal centers adopt a distorted octahedral geometry. It was found that complexes 3–5 initiated the ring-opening polymerization of 1,4-dioxan-2-one (PDO) with high activity.Two lanthanide-lithium heterobimetallic complexes and three monoamido lanthanide complexes were synthesized by silylamine elimination reaction of Ln[N(SiMe3)2]3(μ-Cl)Li(THF)3 or Ln[N(SiMe3)2]3 with quinolinyl aminophenol. All the lanthanide amides show highly catalytic activity for the ring-opening polymerization of 1,4-dioxan-2-one.
Co-reporter:Kun Nie;Tao Feng;FengKui Song;Yong Zhang;HongMei Sun
Science China Chemistry 2014 Volume 57( Issue 8) pp:1106-1116
Publication Date(Web):2014 August
DOI:10.1007/s11426-014-5142-7
A series of neutral bimetallic lanthanide aryloxides p-C6H4[OLnL(THF)n]2 [Ln = Y (1), Yb (2), Sm (3) (n = 1) and La (4) (n = 2), L = Me2NCH2CH2N{CH2-(2-O-C6H2-tBu2-3,5)}2] and alkoxides p-C6H4CH2[OLnL(THF)]2 [Ln = Y (5), Yb (6)] supported by an amine-bridged bis(phenolate) ligand have been synthesized through one-pot reactions of Ln(C5H5)3(THF), LH2 with p-benzenediol and 1,4-benzenedimethanol, respectively. All complexes have been fully characterized by elemental analyses, single-crystal X-ray diffraction analysis, and IR and multi-nuclear NMR spectroscopy (in the cases of 1, 4 and 5). Study of their catalytic behavior revealed that, in general, all complexes are efficient initiators for the polymerization of rac-lactide (LA) and rac-β-butyrolactone (BBL), except for 3 and 4 in the case of BBL. The influence imposed by lanthanides of different ionic radii and initiating groups of different structures on the activity, controllability, and stereoselectivity of polymerization were systematically studied and compared. Highly heterotactic PLA (Pr up to 0.99) and syndiotactic PHB (Pr ≈ 0.81) with high molecular weight and narrow polydispersity formed and were automatically capped with hydroxyl functionality at both ends.
Co-reporter:Chao Wang;Changpeng Chen;Jingyu Zhang;Jian Han;Qian Wang;Kun Guo;Pei Liu;Mingyu Guan;Dr. Yingming Yao;Dr. Yingsheng Zhao
Angewandte Chemie 2014 Volume 126( Issue 37) pp:10042-10046
Publication Date(Web):
DOI:10.1002/ange.201404854
Abstract
An easily synthesized and accessible N,O-bidentate auxiliary has been developed for selective CH activation under palladium catalysis. The novel auxiliary showed its first powerful application in CH functionalization of remote positions. Both C(sp2)H and C(sp3)H bonds at δ- and ε-positions were effectively activated, thus giving tetrahydroquinolines, benzomorpholines, pyrrolidines, and indolines in moderate to excellent yields by palladium-catalyzed intramolecular CH amination.
Co-reporter:Chao Wang;Changpeng Chen;Jingyu Zhang;Jian Han;Qian Wang;Kun Guo;Pei Liu;Mingyu Guan;Dr. Yingming Yao;Dr. Yingsheng Zhao
Angewandte Chemie International Edition 2014 Volume 53( Issue 37) pp:9884-9888
Publication Date(Web):
DOI:10.1002/anie.201404854
Abstract
An easily synthesized and accessible N,O-bidentate auxiliary has been developed for selective CH activation under palladium catalysis. The novel auxiliary showed its first powerful application in CH functionalization of remote positions. Both C(sp2)H and C(sp3)H bonds at δ- and ε-positions were effectively activated, thus giving tetrahydroquinolines, benzomorpholines, pyrrolidines, and indolines in moderate to excellent yields by palladium-catalyzed intramolecular CH amination.
Co-reporter:Qiu Sun, Yaorong Wang, Dan Yuan, Yingming Yao, and Qi Shen
Organometallics 2014 Volume 33(Issue 4) pp:994-1001
Publication Date(Web):February 6, 2014
DOI:10.1021/om401158a
Zirconium and titanium complexes 1 and 2, bearing an amine-bridged bis(phenolato) ligand, have been synthesized and characterized. Although 1 and 2 were inactive in catalyzing intermolecular hydroamination reactions, cationic complexes generated in situ from treatment of 1 and 2 with borate [Ph3C][B(C6F5)4], respectively, were found to be highly active. In general, excellent yields (up to >99%) and 100% regioselectivity for a broad range of terminal alkynes and anilines were observed within a reaction time of 1 h. Reactions with internal alkynes of moderate sterics also led to good yields and moderate regioselectivity. A kinetic study was also conducted, which provided some insights into the mechanism of hydroamination reactions.
Co-reporter:Yinyin Jiang, Xi Zhu, Muzi Chen, Yaorong Wang, Yingming Yao, Bing Wu, and Qi Shen
Organometallics 2014 Volume 33(Issue 8) pp:1972-1976
Publication Date(Web):April 14, 2014
DOI:10.1021/om5000198
The formation of mixed-valent ytterbium and europium complexes L4LnIII2LnII (Ln = Yb (1), Eu (2)) was observed for the first time in the spontaneous reduction reaction system of quinolinyl aminophenol (H2L) with Ln[N(SiMe3)2]3 (Ln = Yb, Eu) in toluene at 90 °C, whereas the same reaction with Sm[N(SiMe3)2]3 gave the expected monoamido samarium complex LSmN(SiMe3)2(DME) (4). The isolation of the binuclear ytterbium complex L3Yb2 (3) under mild conditions demonstrates that the transformation from a trivalent ytterbium complex to the mixed-valent ytterbium species 1 may involve a ligand redistribution reaction and homolysis of the Yb–N bond.
Co-reporter:Tinghua Zeng, Yaorong Wang, Qi Shen, Yingming Yao, Yunjie Luo, and Dongmei Cui
Organometallics 2014 Volume 33(Issue 23) pp:6803-6811
Publication Date(Web):November 19, 2014
DOI:10.1021/om5008242
A series of neutral yttrium guanidinates supported by an amine-bridged bis(phenolate) ligand were synthesized, and their catalytic behaviors for the ring-opening polymerization of 1,4-dioxan-2-one (p-dioxanone, PDO) were explored. Metathesis reactions of amine-bridged bis(phenolate) yttrium chlorides LLnCl(THF) [L = Me2NCH2CH2N{CH2-(2-OC6H2-tBu2-3,5)}2] with corresponding lithium guanidinates generated in situ in a 1:1 molar ratio in THF gave the neutral yttrium guanidinates LY[R2NC(NR1)2] [R1 = −Cy, R2N = −N(TMS)2 (1), −NiPr2 (2), −N(CH2)5 (3); R1 = −iPr, R2N = −NiPr2 (4) −NPh2 (5))]. These complexes were well characterized by elemental analyses, IR, and NMR spectroscopy. The definitive molecular structures of these complexes were determined by single-crystal X-ray analysis. It was found that these complexes can efficiently initiate the ring-opening polymerization (ROP) of PDO, and the catalytic activity is affected by the nature of the guanidinate groups with the active sequence of 1 > 2 ≈ 3 ≈ 4 > 5. The influences of reaction conditions such as polymerization time, polymerization temperature, and molar ratio of monomer to initiator on the polymerization were also investigated. The polymerization kinetics of PDO catalyzed by complex 1 is first-order with respect to monomer concentration, and the apparent activation energy amounts to 30.8 kJ mol–1. The mechanistic investigations showed that the ROP of PDO proceeded through a coordination–insertion mechanism with a rupture of the acyl–oxygen bond of the monomer. MALDI-TOF mass spectrum analysis of the oligomer revealed that there are two kinds of polymer chains in this catalytic system, e.g., the linear chains H–[OCH2CH2OCH2CO]n–OH and the PPDO macrocycles.
Co-reporter:Xiangyong Gu, Xiang Li, Yahong Chai, Qi Yang, Pixu Li and Yingming Yao
Green Chemistry 2013 vol. 15(Issue 2) pp:357-361
Publication Date(Web):10 Dec 2012
DOI:10.1039/C2GC36683E
A metal-free aerobic selective sulfoxidation photosensitized by Rose Bengal or solid-supported Rose Bengal has been developed. The reaction utilizes visible light as the driving force and molecular oxygen as the oxidant. Among the advantages of the developed method are its high efficiency and selectivity, extremely simple operation and workup procedure, and minimal waste generation.
Co-reporter:Xiangyong Gu, Ping Lu, Weigang Fan, Pixu Li and Yingming Yao
Organic & Biomolecular Chemistry 2013 vol. 11(Issue 41) pp:7088-7091
Publication Date(Web):03 Sep 2013
DOI:10.1039/C3OB41600C
A visible light-promoted atom transfer Ueno–Stork reaction was developed using Ir(ppy)2(dtb-bpy)PF6 as the sensitizer. 2-Iodoethyl propargyl ethers or 2-iodoethyl allyl ethers were used as the radical precursors to construct tetrahydrofuran-containing fused [6,5] and [5,5] bicyclic frameworks.
Co-reporter:Jinshui Qiu, Min Lu, Yingming Yao, Yong Zhang, Yaorong Wang and Qi Shen
Dalton Transactions 2013 vol. 42(Issue 28) pp:10179-10189
Publication Date(Web):01 May 2013
DOI:10.1039/C3DT50918D
Electronic properties of the aminophenolate groups have obvious effect on the synthesis of aminophenolate lanthanide–lithium complexes. Amine elimination reactions of Ln[N(SiMe3)2]3(μ-Cl)Li(THF)3 with lithium aminophenolates [ArNHCH2(3,5-tBu2C6H2-2-O)Li(THF)]2 (Ar = p-ClC6H4, [ONH]Cl-p; p-BrC6H4, [ONH]Br-p) in tetrahydrofuran (THF) in a 1:2 molar ratio gave the bimetallic lanthanide–lithium amido complexes [NO]Cl-p2Ln[N(SiMe3)2][Li(THF)]2 (Ln = Y (1), Yb (2)), and [NO]Br-p2Ln[N(SiMe3)2][Li(THF)]2 (Ln = Y (3), Yb (4)). When the Ar groups are p-MeOC6H4, ([ONH]MeO-p) and o-MeOC6H4 ([ONH]MeO-o), similar reactions generated the homoleptic lanthanide–lithium complexes [NO]MeO-p3Ln[Li(THF)]3 (Ln = Y (5), Yb (6)) and [NO]MeO-o2Ln[Li(THF)] (Ln = Y (7), Yb (8)) in high isolated yields, respectively. Whereas the bimetallic lanthanide–lithium amido complexes [NO]Cl-o2Ln[N(SiMe3)2][Li(THF)]2 (Ln = Y (9), Yb (10)) can be obtained in good yields, when the Ar group is o-ClC6H4 ([ONH]Cl-o). All of these complexes were well characterized. X-ray structure determination revealed that these complexes have solvated monomeric structures. In complexes 1–4, 9, and 10, the lanthanide atom is five-coordinated by two oxygen atoms and two nitrogen atoms from two aminophenoxy ligands and one nitrogen atom from N(SiMe3)2 group to form a distorted trigonal bipyramidal geometry, whereas in complexes 5–8, the central lanthanide atom is six-coordinated by oxygen atoms, and nitrogen atoms from the aminophenoxy ligands to form a distorted octahedron. It was found that complexes 1–10 are highly efficient initiators for the ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC), affording the polymers with high molecular weights, and the homoleptic heterobimetallic lanthanide complexes showed apparently high activity.
Co-reporter:Song Sun, Hao Ouyang, Yunjie Luo, Yong Zhang, Qi Shen and Yingming Yao
Dalton Transactions 2013 vol. 42(Issue 46) pp:16355-16364
Publication Date(Web):09 Sep 2013
DOI:10.1039/C3DT52014E
The amine elimination of lanthanide tris(amide) complexes with the phenylene-bridged bis(β-diketiminate) ligands PARAMe-H2, METAMe-H2 and PARAPr-H2 (PARAMe-H2 = 2[2,6-Me2C6H3NHC(Me)C(H)C(Me)N]-(para-phenylene), METAMe-H2 = 2[2,6-Me2C6H3NHC(Me)C(H)C(Me)N]-(meta-phenylene), PARAPr-H2 = 2[2,6-iPr2C6H3NHC(Me)C(H)C(Me)N]-(para-phenylene)), and the mono-β-diketiminate ligand L2,6-iPr2Ph-H (2,6-iPr2C6H3)NHC(Me)CHC(Me)N(C6H5)) afforded the bimetallic lanthanide amide complexes PARAMe-{Ln[N(SiMe3)2]2}2 (Ln = Y (1), Sm (2)), METAMe-{Y[N(SiMe3)2]2}2 (3), PARAPr-{Ln[N(HSiMe2)2]2}2 (Ln = Y (4), Sm (5)), and the monomeric complexes L2,6-iPr2Ph-Y[N(SiMe3)2]2 (6) and L2,6-iPr2Ph-Y[N(HSiMe2)2]2 (7). In the presence of AlR3 and on activation with 1 equiv. of [Ph3C][B(C6F5)4], complexes 1–7 showed a high activity toward the 1,4-selective polymerization of isoprene. The heterometallic Y/Al methyl complex [L2,6-iPr2Ph]Y[(μ-Me)2AlMe2]2 (8) was prepared to elucidate the real active precursor in the polymerization.
Co-reporter:Song Sun, Kun Nie, Yufang Tan, Bei Zhao, Yong Zhang, Qi Shen and Yingming Yao
Dalton Transactions 2013 vol. 42(Issue 8) pp:2870-2878
Publication Date(Web):26 Nov 2012
DOI:10.1039/C2DT31597A
A series of neutral bimetallic lanthanide amido complexes supported by rigid phenylene bridged bis(β-diketiminate) ligands were synthesized, and their catalytic behavior for the polymerization of L-lactide and rac-lactide was explored. The amine elimination reaction of Ln[N(TMS)2]3(μ-Cl)Li(THF)3 with PARA-H2, [PARA-H2 = 2[2,6-iPr2C6H3NHC(Me)C(H)C(Me)N]-(para-phenylene)] in a 2:1 molar ratio in THF at 25 °C afforded the corresponding bimetallic lanthanide amido complexes PARA-{Ln[N(SiMe3)2]2}2 [Ln = Nd(1), Sm(2), Y(3)] in high isolated yields. Similar reaction of Nd[N(TMS)2]3(μ-Cl)Li(THF)3 with META-H2, [META-H2 = 2[2,6-iPr2C6H3NHC(Me)C(H)C(Me)N]-(meta-phenylene)] at 90 °C in toluene for about 48 h gave META-{Nd[N(SiMe3)2]2}2 (4). Complexes 1–4 were well characterized by elemental analysis, IR spectroscopy, and their definitive structures were confirmed by an X-ray crystal structure analysis. The coordination environment and coordination geometry around the metal atoms are similar in these complexes. Each of the metal atoms is four-coordinated with two nitrogen atoms from the N,N-chelating β-diketiminate unit, and two nitrogen atoms from two (Me3Si)2N– groups to form a distorted tetrahedron. These complexes can serve as highly active initiators for L-lactide polymerization in toluene. In addition, they also showed high activity towards rac-lactide polymerization in THF at room temperature, giving heterotactic-enriched polymers (Pr ≈ 0.70), and complex 4 displays obviously higher activity in comparison with complex 1.
Co-reporter:Kun Nie, Weikai Gu, Yingming Yao, Yong Zhang, and Qi Shen
Organometallics 2013 Volume 32(Issue 9) pp:2608-2617
Publication Date(Web):April 24, 2013
DOI:10.1021/om4001023
A series of neutral lanthanide complexes supported by ONNO Salalen-type ligands were synthesized, and their catalytic activity for the polymerization of rac-lactide (rac-LA) was explored. The amine elimination reactions of Ln[N(SiMe3)2]3(μ-Cl)Li(THF)3 with the ONNO Salalen-type ligand L1H2 (L1 = (2-O-C6H2-But2-3,5)CH═NCH2CH2N(Me)CH2(2-O-C6H2-But2-3,5)) in a 1:1 molar ratio in tetrahydrofuran (THF) gave the neutral lanthanide amides L1Ln[N(SiMe3)2](THF) (Ln = Y (1), Sm (2), Nd (3)). Reaction of the lanthanide amides with benzyl alcohol produces the dimeric lanthanide alkoxo complex (L1LnOCH2Ph)2 (Ln = Y (4), Sm (5)) in high isolated yield. Y[N(SiMe3)2]3(μ-Cl)Li(THF)3 reacted with the Salalen-type ligand L2H2 (L2 = (2-O-C6H2-But2-3,5)CH═NCH2CH2N(Me)CH2{2-O-C6H2-(CPhMe2)2-3,5}) in a 1:l molar ratio in THF also gave the desired yttrium amide, but this complex could not be separated because of its very good solubility even in n-pentane. The proton exchange reactions of L1H2 and L2H2 with (C5H5)3Ln(THF) in a 1:1 molar ratio in THF and then with 1 equiv of benzyl alcohol gave the desired lanthanide alkoxides [L1Ln(OCH2Ph)]2 (Ln = Y (4), Sm (5), Yb (6)) and [L2Y(OCH2Ph)]2 (7), respectively. Complexes 1–7 were well characterized by elemental analyses, IR spectra, X-ray single-crystal structure determination, and NMR spectroscopy in the case of complexes 1, 4, and 7. Complexes 1–3 are isostructural and have a solvated monomeric structure. The coordination geometry around the lanthanide atom can be best described as a distorted trigonal bipyramid. Complexes 4–7 are dimeric species in the solid state. They all contain a Ln2O2 core bridging through the oxygen atoms of the two OCH2Ph groups. Each of the lanthanide atoms is also six-coordinated to form a distorted octahedron. It was found that all the complexes are efficient initiators for the ring-opening polymerization of rac-LA, giving PLA with good heterotacticity (Pr up to 0.85). The observed order of increase in activity is in agreement with the order of the ionic radii, whereas the stereoselectivity is in reverse order. The steric bulkiness of the substituents on the phenol ring has no obvious impact on the rate and stereocontrolability of the polymerizations. The Ln–O species resulted in more controllable polymerization than the corresponding Ln–N species, and complex 4 can initiate rac-LA polymerization in a controlled manner.
Co-reporter:Song Sun, Qiu Sun, Bei Zhao, Yong Zhang, Qi Shen, and Yingming Yao
Organometallics 2013 Volume 32(Issue 6) pp:1876-1881
Publication Date(Web):March 12, 2013
DOI:10.1021/om400018b
Treatment of META-[Na(THF)2]2 (1; META = {[2,6-iPr2C6H3NC(Me)C(H)C(Me)N]−}2-(m-phenylene)] with 1 equiv of {Ln[N(SiMe3)2]2(μ-Cl)(THF)}2 (Ln = Y, Yb) in toluene at 110 °C afforded bimetallic lanthanide amido complexes bridged by a chloride and a phenyl group, {Ln[N(SiMe3)2]}2(META′)(μ-Cl) (Ln = Y (2), Yb (3)), which formed via unexpected C–H bond activation of the arene ring. However, the same reactions carried out in both THF and toluene at room temperature gave the bimetallic lanthanide amido–chloro complexes {Ln[N(SiMe3)2]2}META{Ln[N(SiMe3)2]Cl(THF)} (Ln = Y (4), Yb (5)). When they were heated to 110 °C in toluene, complexes 4 and 5 were converted to complexes 2 and 3 via amine elimination. All of these complexes were confirmed by elemental analysis, FT-IR, and X-ray structure analysis and by NMR analysis in the cases of complexes 1, 2, and 4.
Co-reporter:Yu-Fang Tan, Xiao-Ping Xu, Kun Guo, Ying-Ming Yao, Yong Zhang, Qi Shen
Polyhedron 2013 Volume 61() pp:218-224
Publication Date(Web):18 September 2013
DOI:10.1016/j.poly.2013.05.055
The synthesis, structure and catalytic activity for the polymerization of l-lactide of samarium complexes supported by the carbon-bridged bis(phenolate) ligand 2,2′-methylene-bis(6-tert-butyl-4-methyl-phenoxo) (MBMP2−) are described. The reaction of (C5H5)3Sm(THF) with MBMPH2 in a 1:1 M ratio in THF at 50 °C produced the bis(phenolato) samarium complex (C5H5)Sm(MBMP)(THF)2 (1) in a nearly quantitative yield. Complex 1 is a useful precursor for synthesizing bis(phenolato) samarium aryloxides. Complex 1 reacted with MBMPH2 in toluene at 80 °C to give the complex (MBMP)Sm(MBMPH)(THF)2 (2). The reactions of complex 1 with some mono-phenols, including 2,6-di-tert-butyl-4-methylphenol, 2,6-diisopropylphenol, 2,6-dimethylphenol and 4-methoxyphenol, in toluene produce the complexes (MBMP)Sm(OC6H2-But2-2,6-Me-4)(THF)2 (3), (MBMP)Sm(OC6H3-Pri2-2,6)(THF)3 (4), (MBMP)Sm(OC6H3-Me2-2,6)(DME)2 (5) and [(MBMP)Sm(OC6H4-OMe-4)(THF)2]2 (6). All of these complexes were well characterized by elemental analyses, IR spectra and single-crystal X-ray structure determination, except for complex 2. It was found that complexes 3–6 are efficient initiators for l-lactide polymerization.A series of samarium aryloxo complexes supported by a carbon-bridged bis(phenolate) ligand was synthesized by the proton exchange reaction using (C5H5)3Sm(THF) as the starting material. It was found that the bulkiness of the aryloxo groups has a profound influence on the solid state structure and the catalytic property of these complexes.
Co-reporter:Xiangyong Gu;Xiang Li;Yue Qu;Qi Yang;Pixu Li;Yingming Yao
Chemistry - A European Journal 2013 Volume 19( Issue 36) pp:11878-11882
Publication Date(Web):
DOI:10.1002/chem.201301943
Co-reporter:Kun Nie, Lei Fang, Yingming Yao, Yong Zhang, Qi Shen, and Yaorong Wang
Inorganic Chemistry 2012 Volume 51(Issue 20) pp:11133-11143
Publication Date(Web):October 2, 2012
DOI:10.1021/ic301746c
A series of neutral lanthanide alkoxides supported by an amine-bridged bis(phenolate) ligand were synthesized, and their catalytic behaviors for the polymerization of rac-lactide (LA) and rac-β-butyrolactone (BBL) were explored. The reactions of (C5H5)3Ln(THF) with amine-bridged bis(phenol) LH2 [L = Me2NCH2CH2N{CH2-(2-OC6H2But2-3,5)}2] in a 1:1 molar ratio in THF for 1 h and then with 1 equiv each of 2,2,2-trifluoroethanol, benzyl alcohol, and 2-propanol gave the neutral lanthanide alkoxides LLn(OCH2CF3)(THF) [Ln = Y (1), Yb (2), Er (3), Sm (4)], LY(OCH2Ph)(THF) (5), and LY(OPri)(THF) (6), respectively. These lanthanide alkoxides are sensitive to moisture, and the yttrium complex [(LY)2(μ-OPri)(μ-OH)] (7) was also isolated as a byproduct during the synthesis of complex 6. Complexes 1–6 were well characterized by elemental analyses and IR and NMR spectroscopy in the cases of complexes 1 and 4–6. The definitive molecular structures of all of these complexes were determined by single-crystal X-ray analysis. It was found that complexes 1–6 can initiate efficiently the ring-opening polymerization of rac-LA and rac-BBL in a controlled manner. For rac-LA, polymerization gave polymers with very narrow molecular weight distributions (PDI ≤ 1.12) and very high heterotacticity (Pr up to 0.99). The observed activity-increasing order is in agreement with the order of the ionic radii, whereas the order for stereoselectivity is in the reverse order. For rac-BBL polymerization, the resultant polymers have narrow molecular distributions (PDI ≤ 1.26) and high syndiotacticity (Pr up to 0.83). It is worth noting that the activity-decreasing order Yb > Er > Y ≫ Sm is observed for rac-BBL polymerization, which is opposite to the order of ionic radii and to the order of activity for rac-LA polymerization. The ionic radii of lanthanide metals have no obvious effect on the stereoselectivity for rac-BBL polymerization, which is quite different from that for rac-LA polymerization. End-group analysis of the oligomer of rac-BBL suggested that elimination side reactions occurred slowly in these systems, which led to chain cleavage and the formation of crotonate (and carboxy) end groups.
Co-reporter:Wenyi Li;Yingming Yao;Yong Zhang ;Qi Shen
Chinese Journal of Chemistry 2012 Volume 30( Issue 3) pp:609-615
Publication Date(Web):
DOI:10.1002/cjoc.201100438
Abstract
The synthesis and characterization of aluminum alkoxide and alkyl complexes stabilized by piperazidine-bridged bis(phenolate) ligands are described. Treatment of ligand precursors H2[ONNO]1 {H2[ONNO]1=1,4-bis(2-hydroxy-3-tert-butyl-5-methylbenzyl)piperazidine} and H2[ONNO]2 {H2[ONNO]2=1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)piperazidine} with AlEt2(OCH2Ph) and AlEt2(OPr-i), which were generated in situ by the reactions of AlEt3 with equivalent of the corresponding alcohols, in a 1:1 molar ratio in THF gave the corresponding aluminum alkoxide complexes [ONNO]1Al(OCH2Ph) (1) and [ONNO]2Al(OPr-i) (2), respectively. The reaction of H2[ONNO]1 with AlEt2(OCH2Ph) in a 1:2 molar ratio in THF afforded a mixture of monometallic aluminum ethyl complex [ONNO]1AlEt (3) and complex 1, which can be isolated by stepwise crystallization. Similarly, H2[ONNO]2 reacted with AlEt2(OPr-i) in a 1:2 molar ratio in THF to give a mixture of aluminum ethyl complex [ONNO]2AlEt (4) and complex 2. Complexes 1 and 2 were also available via treatment of complexes 3 and 4 with 1 equiv. of benzyl alcohol and isopropyl alcohol, respectively. All of these complexes were fully characterized including X-ray structural determination. It was found that complexes 1 to 4 can initiate the ring-opening polymerization of ε-caprolactone, and complexes 1 and 2 showed higher catalytic activity in comparison with complexes 3 and 4.
Co-reporter:Wenyi Li;Yingming Yao;Yong Zhang ;Qi Shen
Chinese Journal of Chemistry 2012 Volume 30( Issue 3) pp:
Publication Date(Web):
DOI:10.1002/cjoc.201290009
Co-reporter:Qingyan Li, Kun Nie, Bin Xu, Yingming Yao, Yong Zhang, Qi Shen
Polyhedron 2012 Volume 31(Issue 1) pp:58-63
Publication Date(Web):4 January 2012
DOI:10.1016/j.poly.2011.08.033
A zwitterionic amine bridged bis(phenolate) ytterbium(III) complex was synthesized, and its reactivity with a zinc cluster was explored. The reaction of (C5H5)3Yb(THF) with the amine bridged bis(phenol) HONNOH [ONNO = Me2NCH2CH2N{CH2-(2-O-C6H2-But2-3,5)}2] in a 1:2 M ratio in toluene at 80 °C produced the zwitterionic ytterbium complex [ONNO]Yb[ONNO(μ4-H)] (1) in a high isolated yield. The reaction of ZnEt2 with 1 equiv of PhCH2OH gave a zinc cluster Zn7Et6(OCH2Ph)8 (2) in a good isolated yield. Complex 1 reacted with complex 2 in a 7:1 M ratio at room temperature to afford the unexpected ligand redistributed product [ONNO]Zn(THF) (3). These complexes were well characterized by elemental analyses, IR spectra and NMR spectroscopy in the case of complexes 2 and 3. The definitive molecular structures of complexes 2 and 3 were determined by single-crystal X-ray analyses.Graphical abstractA new method to approach the zwitterionic amine bridged bis(phenolate) lanthanide(III) complex has been provided, and the reactivity of the zwitterionic ytterbium complex toward a zinc alkyl cluster has been explored.Highlights► A new approach to synthesizing zwitterionic lanthanide complex was provided. ► The reactivity of the zwitterionic lanthanide complex was explored. ► A novel alkylzinc alkoxo cluster was characterized.
Co-reporter:BaoXia Li;RuiPeng Qi;YingMing Yao;Yong Zhang;Qi Shen
Science Bulletin 2012 Volume 57( Issue 34) pp:4442-4447
Publication Date(Web):2012 December
DOI:10.1007/s11434-012-5330-9
Four lanthanum alkoxides stabilized by a carbon-bridged bis(phenolate) ligand were synthesized and their catalytic behavior for the ring-opening polymerization of L-lactide was explored. Reactions of [(MBMP)LaCp(THF)2] (MBMP2− = 2,2′-methylene-bis(6-tert-butyl-4-methyl phenoxo)) with HOCH2Ph, HOCH2CF3, HOCH(CH3)2, and HOCH2CH2N(CH3)2, respectively, in a 1:1 molar ratio in THF gave the dimeric lanthanum alkoxo complexes [(MBMP)Ln(Sm-OR)(THF)2]2 (OR = OCH2Ph (1), OCH2CF3 (2), OCH(CH3)2 (3), OCH2CH2N(CH3)2 (4)]. These complexes were well characterized, and the definitive molecular structure of complex 1 was determined. It was found that complexes 1 to 4 are efficient initiators for the ring-opening polymerization of L-lactide. The structure of the alkoxo groups has a significant effect on the catalytic behavior, and complex 2 can initiate L-lactide polymerization in a controlled manner.
Co-reporter:Jie Zhang, Jinshui Qiu, Yingming Yao, Yong Zhang, Yaorong Wang, and Qi Shen
Organometallics 2012 Volume 31(Issue 8) pp:3138-3148
Publication Date(Web):March 23, 2012
DOI:10.1021/om300036a
A series of neutral lanthanide complexes supported by aminophenoxy ligands were synthesized, and their catalytic behavior in the polymerization of l-lactide and rac-lactide was explored. The amine elimination reactions of equimolar amounts of Ln[N(TMS)2]3(μ-Cl)Li(THF)3 and aminophenol [HONH]1 {[HONH]1 = 2,6-Me2-C6H4NHCH2(3,5-tBu2-C6H2-2-OH)} in toluene gave the dimeric lanthanide complexes {[ON]1Ln[ONH]1}2 (Ln = La (1), Nd (2)), whereas the similar reactions of La[N(TMS)2]3(THF)2 or Ln[N(TMS)2]3(μ-Cl)Li(THF)3 (Ln = Nd, Sm) with the aminophenols [HONH]2 {[HONH]2 = (ο-OCH3-C6H4)NHCH2(3,5-tBu2-C6H2-2-OH} and [HONH]3 {[HONH]3 = (NC5H4)NHCH2(3,5-tBu2-C6H2-2-OH)} generated the neutral aminophenoxy lanthanide amides {[ON]2Ln[N(TMS)2]}2 [Ln = La (3), Nd (4), Sm (5)] and {[ON]3Ln[N(TMS)2](THF)}2 [Ln = La (6), Nd (7), Sm (8)], respectively, in high isolated yields. These complexes have been fully characterized. X-ray structural determination revealed that complexes 1 and 2 have unsolvated centrosymmetric dimeric structures, in which one hydrogen atom belonging to the amino group of the ligand is reserved. Complexes 3–5 are isostructural and have an unsolvated dimeric structure. The coordination geometry around each of the lanthanide metal atoms can be described as a distorted trigonal bipyramid. Complexes 6 and 7 have a solvated dimeric structure, and the lanthanide metal centers have distorted capped trigonal-prismatic geometries. It was found that complexes 3–8 are highly efficient initiators for the ring-opening polymerization of l-lactide and rac-lactide, affording polymers with high molecular weights.
Co-reporter:Wenyi Li, Zhongjian Zhang, Yingming Yao, Yong Zhang, and Qi Shen
Organometallics 2012 Volume 31(Issue 9) pp:3499-3511
Publication Date(Web):April 18, 2012
DOI:10.1021/om201164t
A series of bimetallic and monometallic lanthanide amides stabilized by a piperazidine-bridged bis(phenolato) ligand were successfully prepared, and the factors controlling the formation of these lanthanide amides were elucidated. Reactions of Ln[N(TMS)2]3(μ-Cl)Li(THF)3 (TMS = SiMe3; THF = tetrahydrofuran) with a piperazidine-bridged bis(phenol), H2[ONNO][4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)piperazidine], in a 2:1 molar ratio in THF at 60 °C gave the anionic bimetallic bis(phenolato) lanthanide amido complexes [ONNO]{Ln[N(TMS)2]2(μ-Cl)Li(THF)}2 [Ln = Y (1), Er (2), Eu (3), Sm (4)], whereas the same reactions conducted at room temperature gave the monometallic bis(phenolato) lanthanide amides [ONNO]LnN(TMS)2(THF) [Ln = Y (5), Sm (6)]. Complex 1 can be transformed to a neutral bimetallic bis(phenolato) yttrium amido complex, [ONNO]{Y[N(TMS)2]2}2 (7), by heating a toluene solution to 80 °C. Complex 7 can also be conveniently prepared by the reaction of the yttrium amide Y[N(TMS)2]3 with H2[ONNO] in a 2:1 molar ratio at 60 °C. For neodymium and praseodymium, only the monometallic lanthanide amido complexes [ONNO]LnN(TMS)2(THF) [Ln = Nd (8), Pr (9)] were isolated, even when the reactions were conducted at 60 °C. Furthermore, reaction of H2[ONNO] with the less bulky lanthanide amides Ln[N(SiMe2H)2]3(THF)2 in a 2:1 molar ratio at 60 °C gave the monometallic lanthanide amido complexes [ONNO]Ln[N(SiMe2H)2](THF) [Ln = Yb (10), Y(11), Nd (12)] as neat products; no bimetallic species were formed. All of these complexes were characterized by IR, elemental analyses, and single-crystal X-ray diffraction. Complexes 1, 5, 6, 7, and 11 were further confirmed by NMR spectroscopy. These complexes are highly efficient initiators for the ring-opening polymerization of l-lactide. In addition, complexes 1, 3, 5, 7, and 11 can initiate rac-lactide polymerization with high activity to give heterotactic-rich polylactides.
Co-reporter:Ling-Ling Huang;Xiang-Zong Han;Yong Zhang ;Qi Shen
Applied Organometallic Chemistry 2011 Volume 25( Issue 6) pp:464-469
Publication Date(Web):
DOI:10.1002/aoc.1788
Abstract
The synthesis, characterization and ε-caprolactone polymerization behavior of lanthanide amido complexes stabilized by ferrocene-containing N-aryloxo functionalized β-ketoiminate ligand FcCOCH2C(Me)N(2-HO-5-But-C6H3) (LH2, Fc = ferrocenyl) are described. The lanthanide amido complexes [LLnN(SiMe3)2(THF)]2 [Ln = Nd (1), Sm (2), Yb (3), Y (4)] were synthesized in good yields by the amine elimination reactions of LH2 with Ln[N(SiMe3)2]3(µ-Cl)Li(THF)3 in a 1:1 molar ratio in THF. These complexes were characterized by IR spectroscopy and elemental analysis, and 1H NMR spectroscopy was added for the analysis of complex 4. The definitive molecular structures of complexes 1 and 3 were determined by X-ray diffraction studies. Complexes 1–4 can initiate the ring-opening polymerization of ε-caprolactone with moderate activity. Copyright © 2011 John Wiley & Sons, Ltd.
Co-reporter:Tao Feng;HongMei Peng;YingMing Yao;Yong Zhang;Qi Shen
Science Bulletin 2011 Volume 56( Issue 14) pp:1471-1475
Publication Date(Web):2011 May
DOI:10.1007/s11434-011-4458-3
The synthesis, characterization and luminescent properties of aluminum complexes containing a dianionic N-aryloxo functionalized β-ketoiminate ligand are presented. 4-(2-Hydroxy-5-R-phenyl)imino-2-pentanone (R = Me, L1H2; R = tert-butyl, L2H2) ligands reacted with AlEt3 in tetrahydrofuran to give the aluminum complexes (L1AlEt)2 (1) and (L2AlEt)2 (2) in reasonable isolated yields. X-ray diffraction revealed that complexes 1 and 2 have solvent-free centrosymmetric dimeric structures, and each aluminum center has distorted trigonal bipyramidal geometry. At room temperature, complexes 1 and 2 exhibit blue photoluminescence in acetonitrile with maximum emission wavelengths of 419 and 413 nm, respectively.
Co-reporter:Bin Xu, Lingling Huang, Zijian Yang, Yingming Yao, Yong Zhang, and Qi Shen
Organometallics 2011 Volume 30(Issue 13) pp:3588-3595
Publication Date(Web):June 14, 2011
DOI:10.1021/om200283j
Four heterobimetallic lanthanide–potassium complexes stabilized by the carbon-bridged bis(phenolate) ligand MBMP2– (MBMP = 2,2′-methylene bis(6-tert-butyl-4-methylphenolate)), [{(MBMP)2La(THF)2}2K][K(THF)6] (1), [(MBMP)Nd(μ-MBMP)K(THF)]2 (2), [(THF)2Sm(MBMP)2K(THF)2] (3), and [(THF)2Yb(MBMP)2K(THF)3] (4), were synthesized, and their structural features were provided. It was found that the ionic radii of lanthanide metals have a profound effect on the structures of the heterobimetallic complexes. Complexes 1 to 4 are efficient catalysts for amidation reactions of aldehydes with amines to produce amides in good to excellent yields under mild conditions.
Co-reporter:Jie Zhang, Chao Wang, Min Lu, Ying-Ming Yao, Yong Zhang, Qi Shen
Polyhedron 2011 30(11) pp: 1876-1883
Publication Date(Web):
DOI:10.1016/j.poly.2011.04.045
Co-reporter:Kun Nie, Xiangyong Gu, Yingming Yao, Yong Zhang and Qi Shen
Dalton Transactions 2010 vol. 39(Issue 29) pp:6832-6840
Publication Date(Web):03 Jun 2010
DOI:10.1039/C001888K
A series of neutral lanthanide aryloxides supported by an amine bridged bis(phenolate) ligand were synthesized, and their catalytic behavior for the polymerization of L-lactide was explored. The reactions of (C5H5)3Ln(THF) with amine bridged bis(phenol)LH2 [L = Me2NCH2CH2N{CH2-(2-O-C6H2-But2-3,5)}2] in a 1:1 molar ratio, and then with 1 equivalent of 2,6-diisopropylphenol, p-cresol or 4-methoxyphenol, respectively, in situ in THF gave the neutral lanthanide aryloxides LLn(OC6H3-2,6-Pri2)(THF) [Ln = Nd (1), Sm (2), Yb (3)], LLn(OC6H4-4-CH3)(THF)n [Ln = Nd (4), Sm (5), n = 2; Ln = Y (6), n = 1] and LLn(OC6H4-4-OCH3)(THF)n [Ln = Nd (7), Sm (8), n = 2; Ln = Yb (9), n = 1] in high isolated yields. These complexes were well characterized by elemental analyses, IR spectra and NMR spectroscopy in the case of complex 6. The definitive molecular structures of complexes 1–8 were determined by single-crystal X-ray analyses, which revealed that both the substituents of the aryloxo groups and the ionic radii of the lanthanide metals affect the solid-state structures of the bis(phenolate) lanthanide aryloxides. It was found that complexes 1–9 are efficient initiators for the ring-opening polymerization of L-lactide, and the structures of the aryloxo groups have no obvious effect on the catalytic activity and controllability. A further study revealed that complex 6 can initiate the highly heteroselective ring-opening polymerization of rac-lactide.
Co-reporter:Min Lu, Yingming Yao, Yong Zhang and Qi Shen
Dalton Transactions 2010 vol. 39(Issue 40) pp:9530-9537
Publication Date(Web):03 Sep 2010
DOI:10.1039/C0DT00025F
A dianionic phenoxyamido ligand was the first to be used to stabilize organo-rare-earth metal amido complexes. Amine elimination reaction of Nd[N(TMS)2]3(μ-Cl)Li(THF)3 (TMS = SiMe3) with aminophenol [HNOH] {[HNOH] = N-p-methylphenyl(2-hydroxy-3,5-di-tert-butyl)benzylamine} in a 1:1 molar-ratio gave the anionic phenoxyamido neodymium amide [NO]2Nd[N(TMS)2][Li(THF)]2 (2) in a low isolated yield. A further study revealed that the stoichiometric reactions of Ln[N(TMS)2]3(μ-Cl)Li(THF)3 with the lithium aminophenoxy [HNOLi(THF)]2 (1) in tetrahydrofuran (THF) gave the anionic rare-earth metal amido complexes [NO]2Ln[N(TMS)2][Li(THF)]2 [Ln = Nd (2), Sm (3), Yb (4), Y (5)] in high isolated yields. All of these complexes are fully characterized. X-Ray structure determination revealed that complex 1 has a solvated dimeric structure, and complexes 2–5 are isostructural, and have solvated monomeric structures. Each of the rare-earth metal ions is coordinated by two oxygen atoms and two nitrogen atoms from two phenoxyamido ligands and one nitrogen atom from the N(TMS)2 group to form a distorted trigonal bipyramidal geometry. Each of the lithium atoms in complexes 2–5 is coordinated with one oxygen atom and one nitrogen atom from two different phenoxyamido groups, and one oxygen atom from one THF molecule to form a trigonal planar geometry. Furthermore, the catalytic behavior of complexes 2–5 for the ring-opening polymerization of L-lactide was explored.
Co-reporter:Bin Xu;Xiangzong Han;Yingming Yao;Yong Zhang ;Qi Shen
Chinese Journal of Chemistry 2010 Volume 28( Issue 6) pp:1013-1018
Publication Date(Web):
DOI:10.1002/cjoc.201090159
Abstract
The synthesis and characterization of dimeric lanthanide amides stabilized by a dianionic N-aryloxo functionalized β-ketoiminate ligand are described in this paper. Reactions of 4-(2-hydroxy-5-tert-butyl-phenyl)imino-2-pentanone (LH2) with Ln[N(SiMe3)2]3(µ-Cl)Li(THF)3 in a 1:1 molar ratio in THF gave the dimeric lanthanide amido complexes [LLn{N(SiMe3)2}(THF)]2 [Ln=Nd (1), Sm (2), Yb (3), Y (4)] in good isolated yields. These complexes were characterized by IR spectroscopy, elemental analysis, and 1H NMR spectroscopy in the case of complex 4. The definitive molecular structures of complexes 1, 3, and 4 were determined. It was found that complexes 1 to 4 can initiate the ring-opening polymerization of L-lactide.
Co-reporter:Xin-Hua Lu, Meng-Tao Ma, Ying-Ming Yao, Yong Zhang, Qi Shen
Inorganic Chemistry Communications 2010 Volume 13(Issue 12) pp:1566-1568
Publication Date(Web):December 2010
DOI:10.1016/j.inoche.2010.09.013
An ytterbium–lithium inverse crown ether complex stabilized by amine-bridged bis(phenolate) ligands (LYbBr)2(μ4-O)(μ3-Li) (1) [L = Me2NCH2CH2N{CH2-(2-O- C6H2-But2-3,5)}2] was isolated as a byproduct from the reaction of LYbCl(THF) with CH3Li in THF in a very low isolated yield. Further study revealed that the inverse crown ether complexes can be synthesized in a controlled manner by the reaction of bis(phenolate) lanthanide chloride with an in situ mixture of n-BuLi with water in THF. A second inverse crown ether complex (L′YbCl)2(μ4-O)(μ3-Li) (2) [L′ = Me2NCH2CH2N{CH2-(2-O-C6H2-But-3-Me-5)}2] was prepared in high isolated yield and well characterized.Two ytterbium–lithium inverse crown ether complexes have been synthesized and structurally characterized. An efficient and straightforward approach was developed for the controlled synthesis of this kind of complexes.
Co-reporter:Xiang-Yong Gu, Xiang-Zong Han, Ying-Ming Yao, Yong Zhang, Qi Shen
Journal of Organometallic Chemistry 2010 695(25–26) pp: 2726-2731
Publication Date(Web):
DOI:10.1016/j.jorganchem.2010.07.037
Co-reporter:Yunjie Luo, Wenyi Li, Dan Lin, Yingming Yao, Yong Zhang and Qi Shen
Organometallics 2010 Volume 29(Issue 16) pp:3507-3514
Publication Date(Web):July 27, 2010
DOI:10.1021/om100298z
A series of lanthanide alkyl complexes supported by a piperazidine-bridged bis(phenolato) ligand were synthesized, and their catalytic activity for the polymerization of l-lactide was explored. The alkane elimination reaction of Ln(CH2SiMe3)3(THF)2 with H2[ONNO] {H2[ONNO] = 1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)piperazidine} in a 1:1 molar ratio in THF gave the neutral lanthanide alkyl complexes [ONNO]Ln(CH2SiMe3)(THF) [Ln = Y (1), Lu (2), Yb (3), Gd (4)] in high isolated yields. Treatment of a gadolinium tris(alkyl) complex formed in situ from the reaction of anhydrous GdCl3 with 3 equiv of Li(CH2SiMe3) in THF gave a novel “ate” gadolinium alkyl complex, {[ONNO]Gd(CH2SiMe3)(μ-Li)(μ-Cl)}2 (5). All of these complexes are fully characterized including X-ray structural determination. Complexes 1−4 are isomorphous, monomeric, and THF-solvated. The coordination geometry around the lanthanide metals can be best described as a distorted trigonal bipyramid. Complex 5 is dimeric and unsolvated, and each [ONNO]Gd(CH2SiMe3) moiety is connected by two μ-Cl and two μ-Li to form a distorted seven-coordinated capped trigonal-prismatic geometry. It was found that complexes 1−4 are highly efficient initiators for the controlled ring-opening polymerization of l-lactide, giving polymers with high molecular weights and narrow molecular weight distributions, whereas complex 5 exhibited apparently low activity for this polymerization. Complex 1 can also initiate rac-lactide polymerization with high activity, but the stereoselectivity is poor.
Co-reporter:Zhongjian Zhang, Xiaoping Xu, Song Sun, Yingming Yao, Yong Zhang and Qi Shen
Chemical Communications 2009 (Issue 47) pp:7414-7416
Publication Date(Web):05 Nov 2009
DOI:10.1039/B915414K
The “ate” and neutral bimetallic ytterbium bisamido complexes stabilized by a flexible bridged bis(phenolate) group are prepared, which exhibited high activity for the ring-opening polymerization of L-lactide.
Co-reporter:Zhongjian Zhang, Xiaoping Xu, Wenyi Li, Yingming Yao, Yong Zhang, Qi Shen and Yunjie Luo
Inorganic Chemistry 2009 Volume 48(Issue 13) pp:5715-5724
Publication Date(Web):May 26, 2009
DOI:10.1021/ic802177y
A series of neutral rare-earth metal amides supported by an imidazolidine-bridged bis(phenolato) ligand were synthesized, and their catalytic activity for the polymerization of l-lactide was explored. The amine elimination reactions of Ln[N(TMS)2]3(μ-Cl)Li(THF)3 with H2[ONNO] {H2[ONNO] = 1,4-bis(2-hydroxy-3,5-di-tert-butyl-benzyl)-imidazolidine} in a 1:1 molar ratio in tetrahydrofuran (THF) gave the neutral rare-earth metal amides [ONNO]Ln[N(TMS)2](THF) [Ln = La (1), Pr (2), Nd (3), Sm (4), Yb (5), and Y (6)] in high isolated yields. All of these complexes are fully characterized. X-ray structural determination revealed that complexes 1−6 are isostructural and have a solvated monomeric structure. The coordination geometry around each of the rare-earth metal atoms can be best described as a distorted trigonal bipyramid. It was found that complexes 1−6 are efficient initiators for the ring-opening polymerization of l-lactide, and the ionic radii of the central metals have a significant effect on the catalytic activity. A further study revealed that these rare-earth metal amides can initiate l-lactide polymerization in a controlled manner in the presence of 1 equiv of isopropyl alcohol.
Co-reporter:FengKui Song;ChunHui Yan;HongMei Sun;YingMing Yao;Qi Shen
Science Bulletin 2009 Volume 54( Issue 18) pp:3231-3236
Publication Date(Web):2009 September
DOI:10.1007/s11434-009-0434-6
Yttrium complexes stabilized by a diaminobis(phenolate) ligand were synthesized and their catalytic behavior was explored. Reaction of YCl3 with 1 equiv of LNa2 [L= Me2NCH2CH2N{CH2-(2-O-C6H2-tBu2-3, 5)}2] gave the yttrium chloride LYCl(THF) (1) in 92% yield. Complex 1 can be used as starting material to prepare the yttrium amido derivative. Complex 1 reacted with 1 equiv of LiNPh2 in THF to afford the expected yttrium amido complex LYNPh2 (2) in high yield. Both of complexes 1 and 2 have been well detected by elemental analysis, NMR spectra and single-crystal X-ray analysis. It was found that complex 2 can efficiently initiate the ring-opening polymerization of L-lactide and ɛ-caprolactone, and a controlled manner is observed in the former case.
Co-reporter:XiangZong Han;LiangLiang Wu;YingMing Yao;Yong Zhang;Qi Shen
Science Bulletin 2009 Volume 54( Issue 20) pp:
Publication Date(Web):2009 October
DOI:10.1007/s11434-009-0514-7
The synthesis and characterization of dimeric rare-earth amides stabilized by a dianionic N-aryloxo functionalized β-ketoiminate ligand are described. Reactions of 4-(2-hydroxy-5-methyl-phenyl) imino-2-pentanone (LH2) with Ln[N(SiMe3)2]3(μ-Cl)Li(THF)3 in a 1:1 molar ratio in THF gave the dimeric rare-earth amido complexes [LLn{N(SiMe3)2}(THF)]2 [Ln = Nd (1), Sm (2), Yb (3), Y (4)]. These complexes were well characterized, and the definitive molecular structures of complexes 3 and 4 were determined. It was found that complexes 1–4 can initiate the ring-opening polymerization of ɛ-caprolactone, and the ionic radii of the central metals have significant effect on the catalytic activity.
Co-reporter:Xiao-Ping Xu, Rui-Peng Qi, Bin Xu, Ying-Ming Yao, Kun Nie, Yong Zhang, Qi Shen
Polyhedron 2009 28(3) pp: 574-578
Publication Date(Web):
DOI:10.1016/j.poly.2008.11.031
Co-reporter:Hongmei Peng ; Zhenqin Zhang ; Ruipeng Qi ; Yingming Yao ; Yong Zhang ; Qi Shen ;Yanxiang Cheng
Inorganic Chemistry 2008 Volume 47(Issue 21) pp:9828-9835
Publication Date(Web):October 2, 2008
DOI:10.1021/ic8011469
The synthesis and reactivity of a series of sodium and rare-earth metal complexes stabilized by a dianionic N-aryloxo-functionalized β-ketoiminate ligand were presented. The reaction of acetylacetone with 1 equiv of 2-amino-4-methylphenol in absolute ethanol gave the compound 4-(2-hydroxy-5-methylphenyl)imino-2-pentanone (LH2, 1) in high yield. Compound 1 reacted with excess NaH to afford the novel sodium cluster [LNa2(THF)2]4 (2) in good isolated yield. Structure determination revealed that complex 2 has the 22-vertex cage structure. Reactions of complex 2 with anhydrous LnCl3 in a 1:4 molar ratio, after workup, gave the desired lanthanide chlorides [LLnCl(DME)]2 [Ln = Y (3), Yb (4), Tb (5)] as dimers. A further study revealed that complexes 3−5 are inert for chlorine substitution reactions. (ArO)3Ln(THF) (ArO = 2,6-But2-4-MeC6H2O) reacted with compound 1 in a 1:1 molar ratio in tetrahydrofuran (THF), after workup, to give the desired rare-earth metal aryloxides as dimers [LLn(OAr)(THF)]2 [Ln = Nd (6), Sm (7), Yb (8), Y (9)] in high isolated yields. All of these complexes are well characterized, and the definitive molecular structures of complexes 2 and 4−6 were determined. It was found that complexes 6−9 can be used as efficient initiators for l-lactide polymerization, and the ionic radii of the central metals have a significant effect on the catalytic activity.
Co-reporter:Ruipeng Qi, Bao Liu, Xiaoping Xu, Zijian Yang, Yingming Yao, Yong Zhang and Qi Shen
Dalton Transactions 2008 (Issue 37) pp:5016-5024
Publication Date(Web):23 Jul 2008
DOI:10.1039/B804914A
The synthesis, characterization and reactivity of heteroleptic rare earth metal complexes supported by the carbon-bridged bis(phenolate) ligand 2,2′-methylene-bis(6-tert-butyl-4-methyl-phenoxo) (MBMP2−) are described. Reaction of (C5H5)3Ln(THF) with MBMPH2 in a 1:1.5 molar ratio in THF at 50 °C produced the heteroleptic rare earth metal bis(phenolate) complexes (C5H5)Ln(MBMP)(THF)n (Ln = La, n = 3 (1); Ln = Yb (2), Y (3), n = 2) in nearly quantitative yields. The residual C5H5−groups in complexes 1 to 3 can be substituted by the bridged bis(phenolate) ligands at elevated temperature to give the neutral rare earth metal bis(phenolate) complexes, and the ionic radii have a profound effect on the structures of the final products. Complex 1 reacted with MBMPH2 in a 1:0.5 molar ratio in toluene at 80 °C to produce a dinuclear complex (MBMP)La(THF)(μ-MBMP)2La(THF)2 (4) in good isolated yield; whereas complexes 2 and 3 reacted with MBMPH2 under the same conditions to give (MBMP)Ln(MBMPH)(THF)2 (Ln = Yb (5), Y (6)) as the final products, in which one hydroxyl group of the phenol is coordinated to the rare earth metal in a neutral fashion. The reactivity of complexes 5 and 6 with some metal alkyls was explored. Reaction of complex 5 with 1 equiv. of AlEt3 in toluene at room temperature afforded unexpected ligand redistributed products, and a discrete ion pair ytterbium complex [(MBMP)Yb(THF)2(DME)][(MBMP)2Yb(THF)2] (7) was isolated in moderate yield. Furthermore, reaction of complex 5 with 1 equiv. of ZnEt2 in toluene gave a ligand redistributed complex [(μ-MBMP)Zn(THF)]2 (8) in reasonable isolated yield. Similar reaction of complex 6 with ZnEt2 also afforded complex 8; whereas the reaction of complex 5 with 1 equiv. of n-BuLi in THF afforded the heterodimetallic complex [(THF)Yb(MBMP)2Li(THF)2] (9). All of these complexes were well characterized by elemental analyses, IR spectra, and single-crystal structure determination, in the cases of complexes 1, 2 and 4–9.
Co-reporter:Bang-Yu Li, Ying-Ming Yao, Yao-Rong Wang, Yong Zhang, Qi Shen
Inorganic Chemistry Communications 2008 Volume 11(Issue 3) pp:349-352
Publication Date(Web):March 2008
DOI:10.1016/j.inoche.2007.12.035
SmCl3 reacted with sodium salt of the Schiff base ligand L (L=3,5-Bu2t-2-O–C6H2CH–N-8-C9H6N) in a 1:2 molar ratio in THF to afford samarium Schiff base chloride L2SmCl(THF) (1). Treatment of complex 1 with excessive metallic sodium produced an unprecedented samarium complex [Na(DME)3][SmL3′Na(DME)] (2), in which three Schiff base ligands were trimerized to form the new ligand L3′ by the reductive coupling reactions of imine groups involving a rare coupling reaction of CN bond of quinoline ring with imine group of Schiff base ligand.Reduction of samarium Schiff base chloride L2SmCl(THF) (1) (L=3,5-Bu2t-2-O–C6H2CH–N–8-C9H6N) with excessive metallic sodium produced an unprecedented samarium complex [Na(DME)3][SmL3′Na(DME)] (2), in which three Schiff base ligands were trimerized to form the new ligand L3′ by the reductive coupling reactions of imine groups involving a rare coupling reaction of CN bond of quinoline ring with imine group of Schiff base ligand.
Co-reporter:Bangyu LI, Yingming YAO, Yaorong WANG, Yong ZHANG, Qi SHEN
Journal of Rare Earths 2008 Volume 26(Issue 4) pp:469-472
Publication Date(Web):August 2008
DOI:10.1016/S1002-0721(08)60120-9
The lanthanide complexes containing a bulky tridentate [N,N,O] Schiff base ligand 3,5-But2-2-(OH)C6H2CH=N-8-C9H6N (HL) were synthesized and characterized. The reaction of anhydrous LnCl3 with NaL formed in situ in a 1:1 molar ratio in THF at room temperature afforded the lanthanide Schiff base dichloride complexes LnLCl2(DME) (Ln=Eu (1); Sm (2)). Complexes 1 and 2 can be used as precursors for the synthesis of the lanthanide cyclopentadienyl Schiff base derivatives. The reactions of complexes 1 and 2 with one equiv of NaCH3C5H4 in THF provided the desired products LnL(CH3C5H4)Cl(THF)·THF (Ln=Eu (3); Sm (4)) in good isolated yields. These complexes were characterized by elemental analysis, IR spectra, and X-ray structural determination, in the case of complexes 3 and 4. The crystal data of complex 3 are monoclinic, P21/c space group, a=1.3370(2) nm, b=1.5190(2) nm, c=1.8910(3) nm, β=109.846(4)°, V=3.6125(8) nm3, Z=4, Dc=1.416 mg/m3, μ=1.847 mm−1, F(000)=1584, R=0.0707, wR=0.1350. The crystal data of complex 4 are monoclinic, P21/c space group, a=1.3383(1) nm, b=1.5210(2) nm, c=1.8960(2) nm, β =109.878(3)°, V=3.6293(7) nm3, Z=4, Dc=1.407 mg/m3, μ=1.728 mm−1, F(000)=1580, R=0.0670, wR=0.1385.
Co-reporter:MingLun Pang;YingMing Yao;Yong Zhang;Qi Shen
Science Bulletin 2008 Volume 53( Issue 13) pp:1978-1982
Publication Date(Web):2008 July
DOI:10.1007/s11434-008-0257-x
Reaction of homoleptic yttrium tris-alkyl complex YR3(R=CH2C6H4NMe2-o) with 1 equivalent of amine bis(phenol)s LH2 (L=Me2NCH2CH2N(CH2-(2-O-C6H2-Bu22-3,5))2) afforded the solvent-free yttrium alkyl complex LYR (1), which has been characterized with elemental analysis, 1H NMR and IR spectra, and structural determination. The coordination geometry around the center metal atom can be best described as a distorted octahedron. It was found that complex 1 can be used as an efficient catalyst for the Tishchenko reaction.
Co-reporter:Zhou Lanzhi, Wang Yuming, Yao Yingming, Zhang Yong, Shen Qi
Journal of Rare Earths 2007 Volume 25(Issue 5) pp:544-548
Publication Date(Web):October 2007
DOI:10.1016/S1002-0721(07)60559-6
(C5H5), Ln(THF) reacted with amine bis(phenol) LH2 [L = Me2NCH2CH2N {CH2-(2-O-C6H2-But-3-Me-5)}2] in a 1:1 molar ratio in THF to generate the amine bis(phenolato) cyclopentadienyl lanthanide complexes LLn(C5H5) (THF) · (THF)n (Ln = La (1), n = 0; Ln = Sm(2), n = 1) in high yields. Complexes 1 and 2 were fully characterized by elemental analysis, NMR (for 1) and IR spectra, and X-ray structural determination. The crystal data of complex 1 are monoclinic, P21/c space group, a = 1.1595(1) nm, b = 1.8588(2) nm, c = 1.6647(1) nm, β = 98.490(2)°, V = 3.5486(5) nm3, Z=4, Dc = 1.338 mg · m−3, μ = 1.240 mm−1, F(000) = 1488, R = 0.0249, wR = 0.0568. The crystal data of complex 2 are monoclinic, P21/c space group, a = 0.9692(1) nm, b = 1.4583(2) nm, c = 2.8192(3) nm, β = 96.805(2)°, V = 3.9584(7) nm3, Z = 4, Dc = 1.340 mg · m−3, μ = 1.524 mm−1, F(000) = 1668, R = 0.0346, wR = 0.0756. The attempts failed to synthesize the amine bis (phenolate) lanthanide alkoxides by the reactions of complexes 1 and 2 with alcohols. The preliminary results revealed that complex 1 can initiate ɛ-caprolactone polymerization.
Co-reporter:YingMing Yao;Qi Shen;Wing Tak Wong
Science Bulletin 2007 Volume 52( Issue 4) pp:467-470
Publication Date(Web):2007 February
DOI:10.1007/s11434-007-0048-9
The lanthanide coordination polymers bearing a 13-membered macrocycle, [(13-EDTA-pnOH)H2] were synthesized. The products [Ln(13-EDTA-pnOH)(H2O)2·NO3]n (Ln = Eu(1), Tb(2), Dy(3)) have been obtained by MS, IR and element analyses. The solid-state structure of 1 was established by single-crystal X-ray analysis. The coordination geometry around the central metal atom in complex 1 is a nine-coordinated, tricapped-trigonal prism having six donor atoms (two amine nitrogen atoms, two amide oxygen atoms and two carboxymethyl oxygen atoms) from one ligand, one oxygen atom from a neighboring ligand, and two more oxygen atoms from two water molecules. The europium atoms are linked by-Eu-O-C-O-Eu-bridges to form an infinite chain.
Co-reporter:XiaoPing Xu;YingMing Yao;Yong Zhang;Qi Shen
Science Bulletin 2007 Volume 52( Issue 12) pp:1623-1628
Publication Date(Web):2007 June
DOI:10.1007/s11434-007-0251-8
Lanthanide methoxides supported by carbon-bridged bis(phenolate) ligands 2,2′-methylene-bis(6-tert-butyl-4-methylphenoxo) (MBMP2−) [(MBMP)Ln(µ-OMe)(THF)2]2 (Ln = Nd (1), Yb (2)) were synthesized in high yields by the protolysis reaction using (C5H5)3Ln(THF) as starting materials, and complex 1 was structurally characterized. The coordination geometry around the center metal can be best described as a distorted octahedron. Complexes 1 and 2 were shown to be efficient initiators for the ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC) and L-lactide. The mechanism of DTC polymerization was explored by the end group analysis of the oligomer.
Co-reporter:Xiaoping Xu;Yingming Yao;Mingyu Hu;Yong Zhang;Qi Shen
Journal of Polymer Science Part A: Polymer Chemistry 2006 Volume 44(Issue 15) pp:4409-4419
Publication Date(Web):20 JUN 2006
DOI:10.1002/pola.21550
Lanthanide isopropoxides supported by carbon-bridged bisphenolate ligands of 2,2′-ethylene-bis(4,6-di-tert-butylphenoxo) {[(EDBP)Ln(μ-OPri)(THF)2]2, where Ln is Nd (1), Sm (2), or Yb (3) and THF is tetrahydrofuran} were synthesized by protic exchange reactions in high yields with Cp3Ln compounds as raw materials, and complex 1 was structurally characterized. Complexes 1–3 were shown to be efficient initiators for the ring-opening polymerization of ε-caprolactone (ε-CL) and 2,2-dimethyltrimethylene carbonate (DTC). Complexes 1–3 could initiate the controlled polymerization of ε-CL, and the polymerization rate was first-order with respect to the monomer. The influence of the reaction conditions on the monomer conversion, molecular weight, and molecular weight distribution of the resultant polymers was investigated. End-group analyses of the oligomers of ε-CL and DTC showed that the polymerization underwent a coordination–insertion mechanism. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4409–4419, 2006
Co-reporter:Zhen-Qin Zhang, Ying-Ming Yao, Yong Zhang, Qi Shen, Wing-Tak Wong
Inorganica Chimica Acta 2004 Volume 357(Issue 11) pp:3173-3180
Publication Date(Web):5 August 2004
DOI:10.1016/j.ica.2004.03.022
Reactions of the β-diketiminate lithium salt L2Li [L2={(2,6-Me2C6H3)NC(Me)}2CH] with anhydrous LnCl3 (Ln=Yb, Sm, Nd) in 1:1 molar ratio in THF afforded the new β-diketiminate lanthanide complexes L2LnCl(THF)(μ-Cl)2Li(THF)2 (Ln=Yb (1), Sm (2), Nd (3)). Recrystallization of complexes 1–3 from toluene gave the neutral complexes L2LnCl2(THF)2 (Ln=Yb (4), Sm (5), Nd (6)). Recrystallization of complexes 4 and 5 in hot toluene for two times gave the dinuclear complexes L2ClLn(μ-Cl)3LnL2(THF) (Ln=Yb (7), Sm (8)). Treatment of the mother liquor of complex 2 in hot toluene for three times gave the novel trinuclear complex L2SmCl(μ-Cl)3SmL2(μ-Cl)Li(L2H)(THF) (9). Each of these complexes was well characterized, while complexes 3, 7 and 9 have been characterized by X-ray diffraction structure determination.A series of lanthanide dichlorides supported by β-diketiminate L [L={(2,6-Me2C6H3)NC(Me)}2CH] were synthesized, and well characterized. These complexes show structural diversity under different crystallization conditions.
Co-reporter:Xiaoping Xu;Yingming Yao;Yong Zhang;Qi Shen
Applied Organometallic Chemistry 2004 Volume 18(Issue 8) pp:
Publication Date(Web):10 AUG 2004
DOI:10.1002/aoc.667
A low-coordinate aryloxo erbium complex, [(ArO)3Er(THF)](MePh), has been synthesized by the reaction of anhydrous ErCl3 with three equivalents of NaOAr in tetrahydrofuran. The central erbium atom is coordinated by three oxygen atoms of the aryloxo ligands and one oxygen atom of the tetrahydrofuran molecule, resulting in a distorted tetrahedron. Copyright © 2004 John Wiley & Sons, Ltd.
Co-reporter:Ying-Ming Yao;Qi Shen;Wing-Tak Wong
Chinese Journal of Chemistry 2003 Volume 21(Issue 9) pp:
Publication Date(Web):26 AUG 2010
DOI:10.1002/cjoc.20030210922
Two new 15-membered functionalized macrocycles, dioxo-polyazacycloalkanes with three pendant acetato groups, have been synthesized by the condensation reaction of DTP A dianhydride (DTPA = diethylenetriaminepentaacetic acid) with 1,2-diaminopropane, (15-DTPA-1, 2-pn), or 1, 2-diaminocyclohexane, (15-DTPA-1,2-cy). Their lanthanide complexes [Ln(15-DTPA-1, 2-pn) (H2O)]2[Ln = Eu (1), Gd (2)] and [Ln(15-DTPA-1,2-cy)(H2O)]2[Ln = Eu (3), Gd (4)] were also prepared. Single crystal X-ray diffraction analyses of complexes 2 and 4 show that they have dimeric structures in solid state; each metal ion is nine-coordinated in a distorted tricapped-trigonal prism. In complex 4, the coexistence of two diastereoisomeric molecules in the crystal lattice was observed.
Co-reporter:Ruipeng Qi, Bao Liu, Xiaoping Xu, Zijian Yang, Yingming Yao, Yong Zhang and Qi Shen
Dalton Transactions 2008(Issue 37) pp:NaN5024-5024
Publication Date(Web):2008/07/23
DOI:10.1039/B804914A
The synthesis, characterization and reactivity of heteroleptic rare earth metal complexes supported by the carbon-bridged bis(phenolate) ligand 2,2′-methylene-bis(6-tert-butyl-4-methyl-phenoxo) (MBMP2−) are described. Reaction of (C5H5)3Ln(THF) with MBMPH2 in a 1:1.5 molar ratio in THF at 50 °C produced the heteroleptic rare earth metal bis(phenolate) complexes (C5H5)Ln(MBMP)(THF)n (Ln = La, n = 3 (1); Ln = Yb (2), Y (3), n = 2) in nearly quantitative yields. The residual C5H5−groups in complexes 1 to 3 can be substituted by the bridged bis(phenolate) ligands at elevated temperature to give the neutral rare earth metal bis(phenolate) complexes, and the ionic radii have a profound effect on the structures of the final products. Complex 1 reacted with MBMPH2 in a 1:0.5 molar ratio in toluene at 80 °C to produce a dinuclear complex (MBMP)La(THF)(μ-MBMP)2La(THF)2 (4) in good isolated yield; whereas complexes 2 and 3 reacted with MBMPH2 under the same conditions to give (MBMP)Ln(MBMPH)(THF)2 (Ln = Yb (5), Y (6)) as the final products, in which one hydroxyl group of the phenol is coordinated to the rare earth metal in a neutral fashion. The reactivity of complexes 5 and 6 with some metal alkyls was explored. Reaction of complex 5 with 1 equiv. of AlEt3 in toluene at room temperature afforded unexpected ligand redistributed products, and a discrete ion pair ytterbium complex [(MBMP)Yb(THF)2(DME)][(MBMP)2Yb(THF)2] (7) was isolated in moderate yield. Furthermore, reaction of complex 5 with 1 equiv. of ZnEt2 in toluene gave a ligand redistributed complex [(μ-MBMP)Zn(THF)]2 (8) in reasonable isolated yield. Similar reaction of complex 6 with ZnEt2 also afforded complex 8; whereas the reaction of complex 5 with 1 equiv. of n-BuLi in THF afforded the heterodimetallic complex [(THF)Yb(MBMP)2Li(THF)2] (9). All of these complexes were well characterized by elemental analyses, IR spectra, and single-crystal structure determination, in the cases of complexes 1, 2 and 4–9.
Co-reporter:Min Lu, Yingming Yao, Yong Zhang and Qi Shen
Dalton Transactions 2010 - vol. 39(Issue 40) pp:NaN9537-9537
Publication Date(Web):2010/09/03
DOI:10.1039/C0DT00025F
A dianionic phenoxyamido ligand was the first to be used to stabilize organo-rare-earth metal amido complexes. Amine elimination reaction of Nd[N(TMS)2]3(μ-Cl)Li(THF)3 (TMS = SiMe3) with aminophenol [HNOH] {[HNOH] = N-p-methylphenyl(2-hydroxy-3,5-di-tert-butyl)benzylamine} in a 1:1 molar-ratio gave the anionic phenoxyamido neodymium amide [NO]2Nd[N(TMS)2][Li(THF)]2 (2) in a low isolated yield. A further study revealed that the stoichiometric reactions of Ln[N(TMS)2]3(μ-Cl)Li(THF)3 with the lithium aminophenoxy [HNOLi(THF)]2 (1) in tetrahydrofuran (THF) gave the anionic rare-earth metal amido complexes [NO]2Ln[N(TMS)2][Li(THF)]2 [Ln = Nd (2), Sm (3), Yb (4), Y (5)] in high isolated yields. All of these complexes are fully characterized. X-Ray structure determination revealed that complex 1 has a solvated dimeric structure, and complexes 2–5 are isostructural, and have solvated monomeric structures. Each of the rare-earth metal ions is coordinated by two oxygen atoms and two nitrogen atoms from two phenoxyamido ligands and one nitrogen atom from the N(TMS)2 group to form a distorted trigonal bipyramidal geometry. Each of the lithium atoms in complexes 2–5 is coordinated with one oxygen atom and one nitrogen atom from two different phenoxyamido groups, and one oxygen atom from one THF molecule to form a trigonal planar geometry. Furthermore, the catalytic behavior of complexes 2–5 for the ring-opening polymerization of L-lactide was explored.
Co-reporter:Song Sun, Hao Ouyang, Yunjie Luo, Yong Zhang, Qi Shen and Yingming Yao
Dalton Transactions 2013 - vol. 42(Issue 46) pp:NaN16364-16364
Publication Date(Web):2013/09/09
DOI:10.1039/C3DT52014E
The amine elimination of lanthanide tris(amide) complexes with the phenylene-bridged bis(β-diketiminate) ligands PARAMe-H2, METAMe-H2 and PARAPr-H2 (PARAMe-H2 = 2[2,6-Me2C6H3NHC(Me)C(H)C(Me)N]-(para-phenylene), METAMe-H2 = 2[2,6-Me2C6H3NHC(Me)C(H)C(Me)N]-(meta-phenylene), PARAPr-H2 = 2[2,6-iPr2C6H3NHC(Me)C(H)C(Me)N]-(para-phenylene)), and the mono-β-diketiminate ligand L2,6-iPr2Ph-H (2,6-iPr2C6H3)NHC(Me)CHC(Me)N(C6H5)) afforded the bimetallic lanthanide amide complexes PARAMe-{Ln[N(SiMe3)2]2}2 (Ln = Y (1), Sm (2)), METAMe-{Y[N(SiMe3)2]2}2 (3), PARAPr-{Ln[N(HSiMe2)2]2}2 (Ln = Y (4), Sm (5)), and the monomeric complexes L2,6-iPr2Ph-Y[N(SiMe3)2]2 (6) and L2,6-iPr2Ph-Y[N(HSiMe2)2]2 (7). In the presence of AlR3 and on activation with 1 equiv. of [Ph3C][B(C6F5)4], complexes 1–7 showed a high activity toward the 1,4-selective polymerization of isoprene. The heterometallic Y/Al methyl complex [L2,6-iPr2Ph]Y[(μ-Me)2AlMe2]2 (8) was prepared to elucidate the real active precursor in the polymerization.
Co-reporter:Jinshui Qiu, Min Lu, Yingming Yao, Yong Zhang, Yaorong Wang and Qi Shen
Dalton Transactions 2013 - vol. 42(Issue 28) pp:NaN10189-10189
Publication Date(Web):2013/05/01
DOI:10.1039/C3DT50918D
Electronic properties of the aminophenolate groups have obvious effect on the synthesis of aminophenolate lanthanide–lithium complexes. Amine elimination reactions of Ln[N(SiMe3)2]3(μ-Cl)Li(THF)3 with lithium aminophenolates [ArNHCH2(3,5-tBu2C6H2-2-O)Li(THF)]2 (Ar = p-ClC6H4, [ONH]Cl-p; p-BrC6H4, [ONH]Br-p) in tetrahydrofuran (THF) in a 1:2 molar ratio gave the bimetallic lanthanide–lithium amido complexes [NO]Cl-p2Ln[N(SiMe3)2][Li(THF)]2 (Ln = Y (1), Yb (2)), and [NO]Br-p2Ln[N(SiMe3)2][Li(THF)]2 (Ln = Y (3), Yb (4)). When the Ar groups are p-MeOC6H4, ([ONH]MeO-p) and o-MeOC6H4 ([ONH]MeO-o), similar reactions generated the homoleptic lanthanide–lithium complexes [NO]MeO-p3Ln[Li(THF)]3 (Ln = Y (5), Yb (6)) and [NO]MeO-o2Ln[Li(THF)] (Ln = Y (7), Yb (8)) in high isolated yields, respectively. Whereas the bimetallic lanthanide–lithium amido complexes [NO]Cl-o2Ln[N(SiMe3)2][Li(THF)]2 (Ln = Y (9), Yb (10)) can be obtained in good yields, when the Ar group is o-ClC6H4 ([ONH]Cl-o). All of these complexes were well characterized. X-ray structure determination revealed that these complexes have solvated monomeric structures. In complexes 1–4, 9, and 10, the lanthanide atom is five-coordinated by two oxygen atoms and two nitrogen atoms from two aminophenoxy ligands and one nitrogen atom from N(SiMe3)2 group to form a distorted trigonal bipyramidal geometry, whereas in complexes 5–8, the central lanthanide atom is six-coordinated by oxygen atoms, and nitrogen atoms from the aminophenoxy ligands to form a distorted octahedron. It was found that complexes 1–10 are highly efficient initiators for the ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC), affording the polymers with high molecular weights, and the homoleptic heterobimetallic lanthanide complexes showed apparently high activity.
Co-reporter:Yu Cui, Weikai Gu, Yaorong Wang, Bei Zhao, Yingming Yao and Qi Shen
Catalysis Science & Technology (2011-Present) 2015 - vol. 5(Issue 6) pp:NaN3312-3312
Publication Date(Web):2015/04/13
DOI:10.1039/C5CY00322A
A series of neutral rare-earth metal aryloxides and amides supported by a new pentadentate (N2O3) salen ligand were synthesized, and their catalytic behaviors for the ring-opening polymerization of rac-lactide (rac-LA) were explored. The protolysis reactions of N,N′-bis(3,5-di-tert-butylsalicylidene)-2,2′-diaminodiphenyl ether (LH2) with (ArO)3Ln(THF) (ArO = 2,6-But2-4-MeC6H2O) and Ln[N(SiMe3)2]3 in a 1:1 molar ratio in THF gave the neutral rare-earth metal aryloxides LLn(OAr)(THF)n [n = 0, Ln = Sc (1), Yb (2); n = 1, Ln = Y (3), Sm (4) and Nd (5)] and rare-earth metal amides LLnN(SiMe3)2 [Ln = Yb (6), Y (7)], respectively. X-ray structural determination showed that complexes 1, 2, 6 and 7 have monomeric structures, in which the coordination geometry around the rare-earth metal atom can be best described as a distorted trigonal prism. Complexes 3 and 5 are THF-solvated monomers and each of the rare-earth metal atoms is seven-coordinated to form a distorted capped trigonal prism. It was found that all of these complexes can efficiently initiate the ring-opening polymerization (ROP) of rac-LA to give heterotactic-rich polylactides (PLAs). The highly heterotactic PLA (Pr up to 0.93) was obtained using complex 2 as the initiator at a polymerization temperature of 0 °C. The observed increasing order of activity of 1 < 2 < 3 < 4 ≈ 5 is in agreement with the order of their ionic radii, whereas the order of stereoselectivity is in the reverse order. The rare-earth metal salen amides can initiate rac-LA polymerization in a controlled manner, while polymerization using the rare-earth metal salen aryloxides is less controlled at room temperature.
Co-reporter:Qiu Sun, Yaorong Wang, Dan Yuan, Yingming Yao and Qi Shen
Chemical Communications 2015 - vol. 51(Issue 36) pp:NaN7636-7636
Publication Date(Web):2015/03/27
DOI:10.1039/C5CC01780G
An in situ generated cationic zirconium complex stabilized by an n-butylamine-bridged bis(phenolato) ligand has been developed to catalyse hydroamination reactions of secondary amines, which is the first example of group 4 metal based catalysts capable of mediating intermolecular hydroamination reactions of N-aryl/alkyl amines.
Co-reporter:Jie Qin, Peng Wang, Qingyan Li, Yong Zhang, Dan Yuan and Yingming Yao
Chemical Communications 2014 - vol. 50(Issue 75) pp:NaN10955-10955
Publication Date(Web):2014/03/31
DOI:10.1039/C4CC02065K
Readily available lanthanide complexes stabilized by a bridged poly(phenolate) ligand have been used for the first time as efficient catalysts for the insertion of CO2 into epoxides to generate cyclic carbonates with high activity, high selectivity, and a wide substrate scope under mild conditions.
Co-reporter:Zhongjian Zhang, Xiaoping Xu, Song Sun, Yingming Yao, Yong Zhang and Qi Shen
Chemical Communications 2009(Issue 47) pp:NaN7416-7416
Publication Date(Web):2009/11/05
DOI:10.1039/B915414K
The “ate” and neutral bimetallic ytterbium bisamido complexes stabilized by a flexible bridged bis(phenolate) group are prepared, which exhibited high activity for the ring-opening polymerization of L-lactide.
Co-reporter:Chengwei Liu, Qinqin Qian, Kun Nie, Yaorong Wang, Qi Shen, Dan Yuan and Yingming Yao
Dalton Transactions 2014 - vol. 43(Issue 22) pp:NaN8362-8362
Publication Date(Web):2014/03/19
DOI:10.1039/C4DT00522H
Lanthanide anilido complexes stabilized by the 2,6-diisopropylanilido ligand have been synthesized and characterized, and their catalytic activity for hydrophosphonylation reaction was explored. A reaction of anhydrous LnCl3 with 5 equivalents of LiNHPh-iPr2-2,6 in THF generated the heterobimetallic lanthanide–lithium anilido complexes (2,6-iPr2PhNH)5LnLi2(THF)2 [Ln = Sm(1), Nd(2), Y(3)] in good isolated yields. These complexes are well characterized by elemental analysis, IR, NMR (for complex 3) and single-crystal structure determination. Complexes 1–3 are isostructural. In these complexes, the lanthanide metal ion is five-coordinated by five nitrogen atoms from five 2,6-diisopropylanilido ligands to form a distorted trigonal bipyramidal geometry. The lithium ion is coordinated by two nitrogen atoms from two 2,6-diisopropylanilido ligands, and one oxygen atom from a THF molecule. It was found that these simple lanthanide anilido complexes are highly efficient for catalyzing hydrophosphonylation reactions of various aldehydes and unactivated ketones to generate α-hydroxyphosphonates in good to excellent yields (up to 99%) within a short time (5 min for aldehydes, 20 min for ketones). Furthermore, the mechanism of hydrophosphonylation reactions has also been elucidated via1H NMR monitoring of reaction.
Co-reporter:Song Sun, Kun Nie, Yufang Tan, Bei Zhao, Yong Zhang, Qi Shen and Yingming Yao
Dalton Transactions 2013 - vol. 42(Issue 8) pp:NaN2878-2878
Publication Date(Web):2012/11/26
DOI:10.1039/C2DT31597A
A series of neutral bimetallic lanthanide amido complexes supported by rigid phenylene bridged bis(β-diketiminate) ligands were synthesized, and their catalytic behavior for the polymerization of L-lactide and rac-lactide was explored. The amine elimination reaction of Ln[N(TMS)2]3(μ-Cl)Li(THF)3 with PARA-H2, [PARA-H2 = 2[2,6-iPr2C6H3NHC(Me)C(H)C(Me)N]-(para-phenylene)] in a 2:1 molar ratio in THF at 25 °C afforded the corresponding bimetallic lanthanide amido complexes PARA-{Ln[N(SiMe3)2]2}2 [Ln = Nd(1), Sm(2), Y(3)] in high isolated yields. Similar reaction of Nd[N(TMS)2]3(μ-Cl)Li(THF)3 with META-H2, [META-H2 = 2[2,6-iPr2C6H3NHC(Me)C(H)C(Me)N]-(meta-phenylene)] at 90 °C in toluene for about 48 h gave META-{Nd[N(SiMe3)2]2}2 (4). Complexes 1–4 were well characterized by elemental analysis, IR spectroscopy, and their definitive structures were confirmed by an X-ray crystal structure analysis. The coordination environment and coordination geometry around the metal atoms are similar in these complexes. Each of the metal atoms is four-coordinated with two nitrogen atoms from the N,N-chelating β-diketiminate unit, and two nitrogen atoms from two (Me3Si)2N– groups to form a distorted tetrahedron. These complexes can serve as highly active initiators for L-lactide polymerization in toluene. In addition, they also showed high activity towards rac-lactide polymerization in THF at room temperature, giving heterotactic-enriched polymers (Pr ≈ 0.70), and complex 4 displays obviously higher activity in comparison with complex 1.
Co-reporter:Qiu Sun, Yaorong Wang, Dan Yuan, Yingming Yao and Qi Shen
Dalton Transactions 2015 - vol. 44(Issue 47) pp:NaN20360-20360
Publication Date(Web):2015/10/01
DOI:10.1039/C5DT02643A
A series of zirconium complexes bearing amine-bridged bis(phenolato) ligands of different steric and electronic properties have been synthesized, and their activities in catalyzing intermolecular hydroamination reactions have been studied and compared. In general, hexacoordinate zirconium dibenzyl complexes 1–4 stabilized by [ONNO]- or [ONOO]-type ligands were found to be less active than pentacoordinate complexes 5 and 7 that carry [ONO]-type ligands, which clearly imply that amine-bridged bis(phenolato) ligands play crucial roles in influencing catalytic activities. Complex 5 showed good activities and regioselectivities in catalysing reactions of various primary amines and alkynes. Moreover, reactions of challenging substrates, including secondary amines, internal alkynes, and hydrazines, were achieved with in situ generated cationic species from complex 5 and [Ph3C][B(C6F5)4].
Co-reporter:Kun Nie, Xiangyong Gu, Yingming Yao, Yong Zhang and Qi Shen
Dalton Transactions 2010 - vol. 39(Issue 29) pp:NaN6840-6840
Publication Date(Web):2010/06/03
DOI:10.1039/C001888K
A series of neutral lanthanide aryloxides supported by an amine bridged bis(phenolate) ligand were synthesized, and their catalytic behavior for the polymerization of L-lactide was explored. The reactions of (C5H5)3Ln(THF) with amine bridged bis(phenol)LH2 [L = Me2NCH2CH2N{CH2-(2-O-C6H2-But2-3,5)}2] in a 1:1 molar ratio, and then with 1 equivalent of 2,6-diisopropylphenol, p-cresol or 4-methoxyphenol, respectively, in situ in THF gave the neutral lanthanide aryloxides LLn(OC6H3-2,6-Pri2)(THF) [Ln = Nd (1), Sm (2), Yb (3)], LLn(OC6H4-4-CH3)(THF)n [Ln = Nd (4), Sm (5), n = 2; Ln = Y (6), n = 1] and LLn(OC6H4-4-OCH3)(THF)n [Ln = Nd (7), Sm (8), n = 2; Ln = Yb (9), n = 1] in high isolated yields. These complexes were well characterized by elemental analyses, IR spectra and NMR spectroscopy in the case of complex 6. The definitive molecular structures of complexes 1–8 were determined by single-crystal X-ray analyses, which revealed that both the substituents of the aryloxo groups and the ionic radii of the lanthanide metals affect the solid-state structures of the bis(phenolate) lanthanide aryloxides. It was found that complexes 1–9 are efficient initiators for the ring-opening polymerization of L-lactide, and the structures of the aryloxo groups have no obvious effect on the catalytic activity and controllability. A further study revealed that complex 6 can initiate the highly heteroselective ring-opening polymerization of rac-lactide.
Co-reporter:Xiangyong Gu, Ping Lu, Weigang Fan, Pixu Li and Yingming Yao
Organic & Biomolecular Chemistry 2013 - vol. 11(Issue 41) pp:NaN7091-7091
Publication Date(Web):2013/09/03
DOI:10.1039/C3OB41600C
A visible light-promoted atom transfer Ueno–Stork reaction was developed using Ir(ppy)2(dtb-bpy)PF6 as the sensitizer. 2-Iodoethyl propargyl ethers or 2-iodoethyl allyl ethers were used as the radical precursors to construct tetrahydrofuran-containing fused [6,5] and [5,5] bicyclic frameworks.
Co-reporter:Ya Xu, Dan Yuan, Yaorong Wang and Yingming Yao
Dalton Transactions 2017 - vol. 46(Issue 18) pp:NaN5855-5855
Publication Date(Web):2017/03/28
DOI:10.1039/C7DT00789B
Different aluminum complexes were synthesized by the reaction of aluminum alkyls with a hexadentate salen-type Schiff base. The reaction of N,N′-bis(3,5-di-tert-butylsalicylidene)-2,2′-(ethylenedioxy)dianiline (LH2) with one equiv. of AlMe3 in toluene at 100 °C proceeded by methane elimination to produce the intermediate methyl complex [AlMeL] (1), and then subsequent intramolecular methyl migration to give the aluminum complex [AlL′] (2) [L′ = (2-O-3,5-tBu2C6H2)CHNC6H4OCH2CH2OC6H4NCH(Me)(2′-O-3′,5′-tBu2C6H2)]. The reaction of the same ligand with AlEt3 under the same experimental conditions involved ethane elimination, ethylene elimination and intramolecular hydrogen migration, and led to the complex [AlL′′] (3) [L′′ = (2-O-3,5-tBu2C6H2)CHNC6H4OCH2CH2OC6H4NCH2(2′-O-3′,5′-tBu2C6H2)]. However, the interaction of two equivalents of AlMe3 and AlEt3 afforded the corresponding binuclear complexes [(AlMe2)2L] (4) and [(AlEt2)2L] (5), respectively, and no methyl or hydrogen migration was found. The solid-state structures of aluminum complexes 1–3 were determined by single-crystal X-ray diffraction. It was found that complexes 2–5 show a very effective catalytic activity for the cycloaddition of epoxides and CO2 in the presence of NBu4Br as a cocatalyst at atmospheric pressure.
Co-reporter:Chao Gong, Hao Ding, Chengrong Lu, Bei Zhao and Yingming Yao
Dalton Transactions 2017 - vol. 46(Issue 18) pp:NaN6038-6038
Publication Date(Web):2017/04/20
DOI:10.1039/C7DT00871F
A divalent ytterbium amidate 1 ([Yb3L6]·2C7H8 for short) was synthesized via amine-elimination of Yb[N(SiMe3)2]2(TMEDA) with an amide proligand N-2,6-diisopropylphenylbenzamide HL (L = 2,6-iPr2C6H3NC(O)Ph) and structurally characterized to be a trinuclear symmetric cluster. Further studies on the reduction of iPrNCNiPr by complex 1 provide Yb(III) complex 2 in hexane–THF ([(YbL2)2(μ-NiPrCNiPr)][YbL3(THF)]·C7H8), which is composed of two subunits in a unit cell, one is a bridged Yb(III) carbene, just the same as complex 4 ([(YbL2)2(μ-NiPrCNiPr)]·3C7H8) obtained in the same reaction in toluene, and the other is a homoleptic monomeric Yb(III) amidate (YbL3). It is also found that complex 2 decomposed to complex 3 ([YbL3]2·2C7H8) and 4 at 90 °C in toluene. Complexes 1–4 were confirmed by X-ray structure determination. Furthermore, complex 4 was proved to be a more active species than its precursor 1 in the catalytic addition of amines to carbodiimides. Finally, complex 1 was found to be an excellent pre-catalyst for the guanylation reaction with a wide scope of substrates.
![Phenol, 2,2',2''-[nitrilotris(methylene)]tris[4,6-dichloro-](http://img.cochemist.com/ccimg/860800/860777-87-3.png)
![Phenol, 2,2',2''-[nitrilotris(methylene)]tris[4,6-dichloro-](http://img.cochemist.com/ccimg/860800/860777-87-3_b.png)
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![PYRROLIDINE, 2-METHYL-1-[(4-NITROPHENYL)METHYL]-4,4-DIPHENYL-](http://img.cochemist.com/ccimg/846600/846577-00-2_b.png)
![2-Azaspiro[4.5]decane, 3-methyl-](http://img.cochemist.com/ccimg/592500/592478-37-0.png)
![2-Azaspiro[4.5]decane, 3-methyl-](http://img.cochemist.com/ccimg/592500/592478-37-0_b.png)
![Pyridine, 2-[(1Z)-2-(diphenylphosphino)ethenyl]-](/data/chemimg/102900/350798-41-3.png)
![Pyridine, 2-[(1Z)-2-(diphenylphosphino)ethenyl]-](/data/chemimg/102900/350798-41-3_b.png)
![3-Penten-2-one, 4-[[2,6-bis(1-methylethyl)phenyl]amino]-](http://img.cochemist.com/ccimg/206000/205993-26-6.png)
![3-Penten-2-one, 4-[[2,6-bis(1-methylethyl)phenyl]amino]-](http://img.cochemist.com/ccimg/206000/205993-26-6_b.png)
![Propanedioic acid, [(1S)-3-oxo-1,3-diphenylpropyl]-, dimethyl ester](http://img.cochemist.com/ccimg/165000/164931-80-0.png)
![Propanedioic acid, [(1S)-3-oxo-1,3-diphenylpropyl]-, dimethyl ester](http://img.cochemist.com/ccimg/165000/164931-80-0_b.png)
![Phosphine, [2-(4-methoxyphenyl)ethyl]diphenyl-](http://img.cochemist.com/ccimg/152100/152076-32-9.png)
![Phosphine, [2-(4-methoxyphenyl)ethyl]diphenyl-](http://img.cochemist.com/ccimg/152100/152076-32-9_b.png)
![PHOSPHINE, [2-(4-CHLOROPHENYL)ETHYL]DIPHENYL-](http://img.cochemist.com/ccimg/152100/152076-31-8.png)
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![2-[[(2-HYDROXY-3,5-DIMETHYLPHENYL)METHYL-(2-HYDROXYETHYL)AMINO]METHYL]-4,6-DIMETHYLPHENOL](/data/chemimg/392300/118328-21-5.png)
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