Co-reporter:Hongyan Xie, Xinli Liu, and Dongmei Cui
Organometallics September 25, 2017 Volume 36(Issue 18) pp:3597-3597
Publication Date(Web):September 1, 2017
DOI:10.1021/acs.organomet.7b00517
The stoichiometric reactions of phosphinimino-amino (PIA)-supported magnesium hydride complex 1, [L1MgH]2 (L1 = (2,6-iPr2-C6H3)NC(Me)CHP(Cy2)N(2,6-Me2-C6H3)), with pyridine N-oxide and 2-phenylpyridine N-oxide afforded 2,4-pentadiene-1-oximate complex 2 and 5-phenyl-2,4-pentadiene-1-oximate complex 3, respectively. The reaction of 1 with 2-methylpyridine N-oxide showed a unique regioselectivity to produce 2,4-hexadiene-1-oximate 4a in toluene and 3,5-hexadiene-2-oximate 4b in THF, respectively. Treatment of β-diketiminato (BDI)-supported magnesium hydride complex 5, [L2MgH]2 (L2 = (2,6-iPr2-C6H3)NC(Me)CHC(Me)N(2,6-iPr2-C6H3)), with quinoline N-oxide gave 1,2-dihydroquinoline type product 6, while treatment of complex 5 with 2-methylpyridine N-oxide either in toluene or THF afforded 1-methyl-2,4-pentadiene-1-oximate complex 7 as the only product. All these complexes were fully characterized by NMR spectroscopy and X-ray diffraction analyses, and mechanism researches were conducted to understand the ring-opening reaction of pyridine N-oxide.
Co-reporter:Fei Lin, Meiyan Wang, and Dongmei Cui
Macromolecules November 14, 2017 Volume 50(Issue 21) pp:8449-8449
Publication Date(Web):October 26, 2017
DOI:10.1021/acs.macromol.7b01928
The polymerization of a nature resourced aromatic compound benzofuran (BF) encounters the problems of low activity and molecular weight. Herein we report BF polymerization initiated by Lewis acids, which showed significant dependence on the type of Lewis acids, reaction solvents, and temperature. When a strong Lewis acid Al(C6F5)3 was used, PBFs with high molecular weights (Mn = 17.9 × 104) and narrow molecular weight distributions (Mw/Mn = 1.56) were achieved for the first time. In addition, these PBFs are amorphous polymer possessing high glass-transition temperature (Tg = 210 °C), good thermal stability (Td,5% loss = 344 °C) as well as high transparency (transmittance >89%). The active species was isolated and characterized through NMR and X-ray diffraction analyses; meanwhile, the polymer chain ends were identified by MALDI–TOF MS and NMR studies, which allowed us to elucidate the mechanism for benzofuran polymerization.
Co-reporter:Dr. Chunji Wu;Dr. Bo Liu;Fei Lin;Dr. Meiyan Wang; Dongmei Cui
Angewandte Chemie 2017 Volume 129(Issue 24) pp:7079-7083
Publication Date(Web):2017/06/06
DOI:10.1002/ange.201702128
AbstractIntroducing ethylene units into polybutadiene backbones is an approach to synthesize advanced rubber materials, which has been a research challenge because of distinct polymerization mechanisms of the two monomers. To date, only trans-1,4- and 1,2-regulated copolymers have been obtained. Herein, we reported the unprecedented cis-1,4 selective copolymerization of ethylene and butadiene by using the thiophene-fused cyclopentadienyl-ligated scandium complexes. The effects of the sterics and electronics of the catalytic precursors as well as the monomer loading mode on the activity and selectivity as well as the sequence lengths were investigated, and the mechanism was elucidated. Thus a novel ethylene-based rubber material possessing a high molecular weight, 80 % cis-1,4 regularity and a Tg=−94 °C without an obvious melting point owing to short polyethylene sequences even at its content up to 45 mol %, was isolated. This new rubber material exhibited excellent anti-flowing performance and strong tensile strength.
Co-reporter:Fei Lin, Meiyan Wang, Yupeng Pan, Tao Tang, Dongmei CuiBo Liu
Macromolecules 2017 Volume 50(Issue 3) pp:
Publication Date(Web):January 18, 2017
DOI:10.1021/acs.macromol.6b02413
The stereoselective and sequence controlled coordination copolymerizations of butadiene (BD) and styrene (St) with diblock, tapered, gradient, and random sequence distributions were achieved for the first time through varying the central metals of the rare-earth metal bis(alkyl) catalyst precursors (Flu-CH2-Py)Ln(CH2SiMe3)2(THF)x (Flu = fluorenyl, Py = pyridyl, x = 1: Ln = Nd(1), Y(2), Tm(3); x = 0, Ln = Sc(4)). The thermal behavior, morphology, and the mechanical property of these copolymers were analyzed, and their relationships were established for the first time. The mechanism of central metal size tuning the sequence distribution was discussed based on DFT calculations.
Co-reporter:Dr. Dongtao Liu;Dr. Meiyan Wang;Zichuan Wang;Dr. Chunji Wu;Yupeng Pan; Dongmei Cui
Angewandte Chemie 2017 Volume 129(Issue 10) pp:2758-2763
Publication Date(Web):2017/03/01
DOI:10.1002/ange.201611066
AbstractStyrene underwent unprecedented coordination–insertion copolymerization with naked polar monomers (ortho-/meta-/para-methoxystyrene) in the presence of a pyridyl methylene fluorenyl yttrium catalyst. High activity (1.26×106 g molY−1 h−1) and excellent syndioselectivity were observed, and high-molecular-weight copolymers (24.6×104 g mol−1) were obtained. The insertion rate of the polar monomers could be adjusted in the full range of 0–100 % simply by changing the loading of the polar styrene monomer. Strikingly, the copolymers had tapered, gradient, and even random sequence distributions, depending on the position of the polar methoxy group on the phenyl ring and thus on its mode of coordination to the active metal center, as shown by tracking the polymerization process and DFT calculations.
Co-reporter:Fei Lin;Zhaohe Liu;Tiantian Wang; Dongmei Cui
Angewandte Chemie International Edition 2017 Volume 56(Issue 46) pp:14653-14657
Publication Date(Web):2017/11/13
DOI:10.1002/anie.201707601
AbstractRare-earth metal complexes (Flu-CH2-Py)Ln(CH2SiMe3)2(THF)n (Ln=Sc(1), Lu(2), Tm(3), Y(4) and Gd(5)), upon the activation of [Ph3C][B(C6F5)4] and AliBu3, were employed to catalyze the polymerization of allene derivatives under mild conditions. The Gd, Y, Tm, Lu metal based precursors exhibited distinguished 2,3-selectivity (>99.9 %) for phenylallene (PA) polymerization, whereas the smallest Sc metal based precursor showed a moderate 2,3-selectivity. The activity increased with the central metal size following the trend of Gd(5)>Tm(4)>Y(3)>Lu(2)>Sc(1). Moreover, Gd(5) also realized the purely 2,3-selective polymerizations of polar or nonpolar allene derivatives, para-methylphenylallene, para-flourophenylallene and para-methoxyphenylallene, regardless of electron-donating or -withdrawing substituents. Owing to the highly regular backbones, these polymers (except PPA) were crystalline, thus being the first crystalline polymers based on allene derivatives.
Co-reporter:Dr. Chunji Wu;Dr. Bo Liu;Fei Lin;Dr. Meiyan Wang; Dongmei Cui
Angewandte Chemie International Edition 2017 Volume 56(Issue 24) pp:6975-6979
Publication Date(Web):2017/06/06
DOI:10.1002/anie.201702128
AbstractIntroducing ethylene units into polybutadiene backbones is an approach to synthesize advanced rubber materials, which has been a research challenge because of distinct polymerization mechanisms of the two monomers. To date, only trans-1,4- and 1,2-regulated copolymers have been obtained. Herein, we reported the unprecedented cis-1,4 selective copolymerization of ethylene and butadiene by using the thiophene-fused cyclopentadienyl-ligated scandium complexes. The effects of the sterics and electronics of the catalytic precursors as well as the monomer loading mode on the activity and selectivity as well as the sequence lengths were investigated, and the mechanism was elucidated. Thus a novel ethylene-based rubber material possessing a high molecular weight, 80 % cis-1,4 regularity and a Tg=−94 °C without an obvious melting point owing to short polyethylene sequences even at its content up to 45 mol %, was isolated. This new rubber material exhibited excellent anti-flowing performance and strong tensile strength.
Co-reporter:
Journal of Polymer Science Part A: Polymer Chemistry 2017 Volume 55(Issue 7) pp:1243-1249
Publication Date(Web):2017/04/01
DOI:10.1002/pola.28489
ABSTRACTBy merit of dual catalysis of the cationic rare-earth complex [(η5-Flu-CH2-Py)Ho(CH2SiMe3)2(THF) (Flu = fluorenyl, Py = pyridyl) for the living polymerizations of butadiene (BD) and styrene (St), the crystalline styrene-butadiene-styrene (SBS) triblock copolymers consisting of elastic polybutadiene (PBD) sequences with suitable 1,4 regularity (about 70%) and crystalline syndiotactic polystyrene (sPS, [rrrr] > 99%) sequences were successfully synthesized through sequential addition of St, BD, and St monomers. The catalytic system showed high polymerization activities for St and BD in a controlled manner. The crystalline styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) triblock copolymers were obtained by hydrogenation of the above SBS copolymers. The observation of a strong endothermic peak at 266 °C in their differential scanning calorimetry (DSC) curves confirmed the existence of the sPS blocks in the crystalline SEBS different from the industrial product Kraton SEBS-1652. Thermal degradation temperature of the crystalline SEBS (418 ± 2 °C) indicated the well thermostability and process window of this polymer. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 55, 1243–1249
Co-reporter:Fei Lin, Xingbao Wang, Yupeng Pan, Meiyan Wang, Bo Liu, Yi Luo, and Dongmei Cui
ACS Catalysis 2016 Volume 6(Issue 1) pp:176
Publication Date(Web):November 23, 2015
DOI:10.1021/acscatal.5b02334
Because of the steric bulkiness and the η5/κ1-constrained-geometry-configuration (CGC) geometry, the entire range of pyridyl-methylene-fluorenyl-stabilized rare earth metal bisalkyl complexes, (Flu-CH2-Py)Ln(CH2SiMe3)2(THF)x (Flu = fluorenyl; Py = pyridyl; for 1, Ln = Sc and x = 0; for 2–11, Ln = Lu, Tm, Er, Ho, Y, Dy, Tb, Gd, Nd, or Pr and x = 1), and monoalkyl complex, (Flu-CH2-Py)2La(CH2SiMe3) (THF) (12), has been successfully achieved for the first time via the sequential salt metathesis reactions. Activated by [Ph3C][B(C6F5)4] and AliBu3, complexes 1–9 showed high activity and perfect syndioselectivity for styrene polymerization, while the large Nd- and Pr-attached precursors 10 and 11 exhibited slightly decreased syndioselectivity but rather low activity; the monoalkyl La precursor 12 was completely inert. The activity increased with the decrease in the rare earth metal size, in striking contrast to the literature that has shown that a large metal facilitates a high activity, which was also not a result of an enthalpic effect (ΔH⧧) or an entropic effect (ΔS⧧) according to Eyring plots. The types of organoborates and the aluminum alkyls, the electron donors, and the polarity of the reaction medium, which affected the coordination of styrene to the active species, aroused significantly different catalytic activity, indicating that styrene coordination played the key role in the polymerization process. On the basis of this, the density functional theory calculation of the active species in the model of [(Flu-CH2-Py)Ln-nC17H19]+ revealed whenever the orbitals of the pyridyl-methylene fluorenyl ligand overlapped with those of the rare earth metals, the LUMO energy of the active species was lowered and thus the catalytic activity was high. Therefore, the LUMO energy of the active species could be adopted as a potential criterion to estimate the activity of a catalytic system for styrene polymerization. This work reveals for the first time the power of the pyridyl-methylene fluorenyl ligand and the nature of the factors influencing the catalytic performance.Keywords: DFT calculation; ligand design; rare-earth metal complexes; styrene polymerization; syndiotactic
Co-reporter:Chuanyang Li, Xinli Liu, Shasha He, Yubin Huang and Dongmei Cui
Polymer Chemistry 2016 vol. 7(Issue 5) pp:1121-1128
Publication Date(Web):18 Dec 2015
DOI:10.1039/C5PY01849H
Using a O,N,N,O-tetradentate Salan yttrium alkyl complex as the precursor and monohydric PEG as the chain transfer agent, rac-LA and MPC monomers were sequentially ring-opening polymerized via living immortal mode to give biodegradable triblock amphiphilic copolymers of (PEG-b-PLA-b-PMPC) (PEG = poly(ethylene glycol) and MPC = 5-methyl-5-propargyloxycarbonyl-propylene carbonate). The subsequent “click” reaction between the azide functionalized AIE fragment tetraphenylethylene TPE-N3 and the alkyne substituent on the PMPC block provided swiftly the first AIE functionalized biodegradable amphiphilic copolymers. These copolymers self-assembled into homogeneous micelles that exhibited a tailored PL intensity and fine AIE performance, and should be attractive candidates for bioimaging and chemosensor applications.
Co-reporter:Changguang Yao, Na Liu, Shiyu Long, Chunji Wu and Dongmei Cui
Polymer Chemistry 2016 vol. 7(Issue 6) pp:1264-1270
Publication Date(Web):21 Dec 2015
DOI:10.1039/C5PY01801C
The unprecedented highly cis-1,4 selective (>99%) coordination–insertion polymerization of the polar monomer 2-(4-methoxyphenyl)-1,3-butadiene (2-MOPB) has been achieved using a β-diketiminato yttrium bis(alkyl) complex to afford a hydrophilic plastic polymer P(2-MOPB) with a water contact angle of 87.7° and glass transition temperature of 34.2 °C. The copolymerization of polar 2-MOPB and non-polar isoprene has also been successfully realized for the first time to produce a type of highly modified cis-1,4 polyisoprene with a wide range of 2-MOPB content (8.2%–88.5%). The composition was adjusted by regulating the monomer feed ratio according to the copolymerization kinetics. Hydrogenation of P(2-MOPB) provided an unusual alternating copolymer, poly(4-methoxystyrene-alt-ethylene) that could not be obtained via any other methods.
Co-reporter:Lei Li, Shihui Li, and Dongmei Cui
Macromolecules 2016 Volume 49(Issue 4) pp:1242-1251
Publication Date(Web):February 5, 2016
DOI:10.1021/acs.macromol.5b02654
Living polymerization of 3-methylenehepta-1,6-diene (MHD) catalyzed by bis(phosphino)carbazoleide-ligated yttrium alkyl complex afforded a new product bearing pendant terminal vinyl groups with high stereotacticity (cis-1,4-selectivity up to 98.5%), proved by the NMR (1H, 13C, and 1D ROESY) spectroscopic analyses, which demonstrates overwhelmingly favorable chemoselectivity toward conjugated diene over α-olefin moieties. High cis-1,4 random copolymers of MHD and isoprene could also be obtained with pendant vinyl groups ranging from 10% to 90%. These vinyl groups in every chain unit can be cleanly and quantitatively converted into various functionalities via light-mediated thiol–ene reaction, resulting in homo- and copolymers of various functional butadiene derivatives, which display versatile thermal properties.
Co-reporter:Zichuan Wang, Dongtao Liu, and Dongmei Cui
Macromolecules 2016 Volume 49(Issue 3) pp:781-787
Publication Date(Web):January 15, 2016
DOI:10.1021/acs.macromol.5b02263
The homopolymerization of a polar monomer, 4-methylthiostyrene (MTS), was successfully achieved by a rare-earth metal based catalyst in the highest activity of 45.1 × 104 g molY–1 h–1 and the excellent syndioselectivity (rrrr > 99%). The polymerization was rather controllable that the resultant poly(methylthiostyrene)s (PMTS) had molecular weights comparable to the theoretic ones reaching up to 1.7 × 105 while the molecular weight distributions were narrow (PDI = 1.3–1.9). Moreover, the copolymerization of this polar MTS with the nonpolar styrene (St) performed fluently under various MTS-to-St ratios in a quasi-living mode. The monomer reactivity ratios were rMTS = 1.08 and rSt = 0.77, following the first Markov statistics, and was close to the ideal random copolymerization. Therefore, a series of unprecedented statistical random copolymers, P(St-r-MTS)s, where the compositions were strictly closed to the monomer fed ratios, had been accessed. Strikingly, both monomer sequences remained highly syndiotactic as their homopolymers regardless of the compositions, thus endowing P(St-r-MTS)s variable glass transition temperatures and melting points. The shortest number-averaged sequence length for these copolymers P(St-r-MTS) crystallizing from the melts was n̅St = 5.75 for PS sequences and n̅MTS = 8.11 for PMTS.
Co-reporter:Rong Wang, Dongtao Liu, Xiaohong Li, Jie Zhang, Dongmei Cui, and Xinhua Wan
Macromolecules 2016 Volume 49(Issue 7) pp:2502-2510
Publication Date(Web):March 23, 2016
DOI:10.1021/acs.macromol.6b00325
A novel vinylbiphenyl monomer, 2-methoxy-5-phenylstyrene (MOPS), was designed and efficiently synthesized to investigate the stereospecific polymerization of bulky and polar styrenic derivative. Regardless of its large side group and electron-donating o-methoxy substituent, this compound showed a high polymerizability and was readily converted to the corresponding polymers with moderate to high molecular mass through radical, anionic, and coordination polymerizations. The resultant polymers were characterized by a combination of 1H/13C NMR spectrometry, thermal analysis, and wide-angle X-ray diffraction. Radical polymerization initiated by AIBN in toluene at 60 °C produced a syndiotactic-rich (rr = 0.37) polymer as most bulky vinyl monomers, whereas anionic polymerizations induced by n-BuLi yielded only isotactic-rich polymers no matter if polar tetrahydrofuran (−78 °C, mm = 0.54) or apolar toluene (−40 °C, mm = 0.78) was employed as the solvent. The isotactic-rich microstructure obtained by anionic polymerization in polar solvent at low temperature, the condition that usually leads to syndiotactic-rich polymer, manifested the strong interactions between the o-methoxy groups of the growing chain end and the penultimate unit with the lithium counterion. Highly isotactic (mm = 0.95) and perfect syndiotactic (rr > 0.99) polymers were obtained via coordination polymerizations in toluene at ambient temperature with the β-diketiminatoyttrium precursor (I) and the heterocyclic-fused cyclopentadienylscandium complex (III) as the catalytic precursor, respectively. All the polymers were thermally stable with 5% weight loss temperatures above 360 °C. They underwent glass transitions in the temperature range of 124–140 °C depending on the tacticity, much higher than polystyrene, implying the dominant role of congestion effect of large side groups on the segment movement restriction of polymer chain. Both isotactic and syndiotactic polymers were crystalline and had melting points higher than 300 °C, although the atactic and less stereoregular polymers were amorphous. The facile synthesis in conjunction with stereostructure tailorability, high thermal stability, glass transition temperature, and melting point makes the polymer a promising candidate for not only helical functional material but also engineering plastics.
Co-reporter:Bo Liu and Dongmei Cui
Macromolecules 2016 Volume 49(Issue 17) pp:6226-6231
Publication Date(Web):August 18, 2016
DOI:10.1021/acs.macromol.6b00904
Chain shuttling polymerization (CSP) has exhibited unique privilege to combine monomer sequences of different properties into one macromolecular chain, which, however, is difficult to achieve because of low chain transfer efficiency and thus lead to poor architecture control over the resulting polymers. Herein, we reported that the pyridyl–methylene fluorenyl scandium complex 1 in combination with [Ph3C][B(C6F5)4] and AliBu3 showed a high transfer efficiency (93.8%) in the presence of 10 equiv of AliBu3 toward the chain-transfer polymerization (CTP) of isoprene (IP) in high 1,4-selectivity (83%). Meanwhile, under the same conditions, the analogous lutetium precursor 3 based system was 3,4-regioselective and exhibited almost perfect chain transfer efficiency (96.5–100%) in a wide range of AliBu3-to-Lu ratios from 10:1 to 100:1, indicating that each Lu generated apparently 100 polyisoprene (PIP) macromolecules. Both CTPs performed fluently without compromising the selectivity and the activity and had comparable chain transfer rate constants. Based on this, 1,4- and 3,4-regioselective CSPs were realized by mixing 1 and 3 in various ratios to give a series of PIPs bearing different distribution of 1,4- and 3,4-PIP sequences and Tg values. This work provides a new strategy to access stereoregular and architecture controlled polymers from a single monomer.
Co-reporter:Bo Liu, Lei Li, Guangping Sun, Dongtao Liu, Shihui Li and Dongmei Cui
Chemical Communications 2015 vol. 51(Issue 6) pp:1039-1041
Publication Date(Web):21 Nov 2014
DOI:10.1039/C4CC08962F
The polymerization of bio-renewable myrcene (MY), using a cationic β-diimidosulfonate lutetium catalyst in high activity, afforded an unprecedented isotactic 3,4-polymyrcene (PMY) with a low Tg (−42 °C). Based on this result, the random and block copolymerization of myrcene and isoprene (IP) resulted in novel elastomers that comprise the amorphous iso-3,4-PMY and iso-3,4-PIP sequences.
Co-reporter:Dongtao Liu, Rong Wang, Meiyan Wang, Chunji Wu, Zichuan Wang, Changguang Yao, Bo Liu, Xinhua Wan and Dongmei Cui
Chemical Communications 2015 vol. 51(Issue 22) pp:4685-4688
Publication Date(Web):06 Feb 2015
DOI:10.1039/C5CC00470E
Unprecedented coordination–insertion polymerizations of polar methoxyl substituted styrene derivatives, in despite of the position of the substituent, have been achieved using a pyridyl methylene fluorenyl yttrium bis(alkyl) precursor with high activity to give polar polystyrenes of high molecular weight and perfect syndiotacticity.
Co-reporter:Weifeng Rong, Dongliang He, Meiyan Wang, Zehuai Mou, Jianhua Cheng, Changguang Yao, Shihui Li, Alexander A. Trifonov, Dmitrii M. Lyubov and Dongmei Cui
Chemical Communications 2015 vol. 51(Issue 24) pp:5063-5065
Publication Date(Web):11 Feb 2015
DOI:10.1039/C4CC07262F
The first neutral rare-earth metal dinuclear dihydrido complexes [(NPNPN)LnH2]2 (2-Ln; Ln = Y, Lu; NPNPN: N[Ph2PNC6H3(iPr)2]2) bearing μ2-bridging hydride ligands have been synthesized. In the presence of THF, 2-Y undergoes intramolecular activation of the sp2 C–H bond to form dinuclear aryl–hydride complex 3-Y containing three μ2-bridging hydride ligands.
Co-reporter:Wei Zhao, Bo Liu, Xinli Liu, Xue Wang, Yang Wang, Changguang Yao, Chunji Wu and Dongmei Cui
Polymer Chemistry 2015 vol. 6(Issue 44) pp:7711-7716
Publication Date(Web):10 Sep 2015
DOI:10.1039/C5PY01164G
A highly efficient strategy for synthesizing hydroxyl-end and amide-core, highly stereoregular, star-shaped polylactide was established by employing a lutetium complex via immortal ROP of rac-lactide with a polyamine as the chain transfer agent.
Co-reporter:Changguang Yao, Hongyan Xie and Dongmei Cui
RSC Advances 2015 vol. 5(Issue 113) pp:93507-93512
Publication Date(Web):02 Nov 2015
DOI:10.1039/C5RA18713C
A series of amidino N-heterocyclic carbene ligand supported rare-earth metal bis(alkyl) complexes (2,6-R12C6H3NCR2NCH2CH2(NCHCHN(C6H2Me3-2,4,6)C))Ln(CH2SiMe3)2 [R1 = iPr, R2 = Ph, Ln = Lu (1a); R1 = iPr, R2 = Ph, Ln = Sc (1b); R1 = iPr, R2 = tBu, Ln = Lu (2a); R1 = Me, R2 = Ph, Ln = Lu (3a)] were synthesized and characterized by NMR spectroscopy. On activation with [(Ph3C)][(B(C6F5)4)], complexes 1a, 2a and 3a exhibited high activities and high 3,4-selectivities (96.9%) for the polymerization of 2-phenyl-1,3-butadiene in a living mode to afford new plastic polydienes with high glass-transition temperatures (44.3–56.1 °C). The 3,4-selectivity decreased with increasing the polymerization temperature (25–60 °C), but increased with polarity of polymerization solvent in the order of chlorobenzene > toluene > cyclohexane. In contrast, complex 1b was almost inert for the polymerization of 2-phenyl-1,3-butadiene owing to its steric bulkiness.
Co-reporter:Zehuai Mou, Hongyan Xie, Meiyan Wang, Na Liu, Changguang Yao, Lei Li, Jingyao Liu, Shihui Li, and Dongmei Cui
Organometallics 2015 Volume 34(Issue 16) pp:3944-3949
Publication Date(Web):August 6, 2015
DOI:10.1021/acs.organomet.5b00413
Treatment of heteroscorpionate zinc benzyloxy complex LZnOBn (1, L = (MePz)2CP(Ph)2NPh, MePz = 3,5-dimethylpyrazolyl) with phenylsilane (PhSiH3) gave a zinc hydride complex LZnH (2) containing a rare terminal hydride fragment. X-ray diffraction analysis and the DFT calculation confirm the zwitterionic structure of complex 2. The stoichiometric reaction of 2 with CS2 readily afforded a dithioformate complex LZnSCH(S) (3) of the C═S insertion into the Zn–H product. Moreover, complex 2 was an efficient catalyst for the hydrosilylation reaction of a series of silanes and aldehydes under mild conditions, featuring excellent functional group tolerance. The preliminary mechanistic study revealed that both zinc benzyloxy complex 1 and zinc hydride complex 2 were involved in the hydrosilylation process as the reaction intermediates.
Co-reporter:Bo Liu, Guangping Sun, Shihui Li, Dongtao Liu, and Dongmei Cui
Organometallics 2015 Volume 34(Issue 16) pp:4063-4068
Publication Date(Web):August 5, 2015
DOI:10.1021/acs.organomet.5b00502
The protonolysis reaction of β-iminophosphonamine ligand (NPNdipp = Ph2P(NC6H3iPr2-2,6)2) with one equivalent of rare-earth-metal tris(alkyl)s afforded the corresponding bis(alkyl) complexes NPNdippLn(CH2SiMe3)2(THF) (Ln = Sc (1), Lu (2), Y (3), Er (4)). The bis(4-methylbenzyl) complexes NPNdippLn(CH2Ph-4-Me)2(THF) (Ln = Nd (5), La (6)) were prepared by treatment of the tris(4-methylbenzyl) compounds Ln(CH2Ph-4-Me)3(THF)3 with β-iminophosphonamine ligand. The small-size rare-earth-metal-based complexes 1–4 upon activation with AliBu3 and [Ph3C][B(C6F5)4] showed high 3,4-selectivities up to 98.1% for isoprene polymerization. When the larger size rare-earth-metal-based 4-methylbenzyl complexes 5 and 6 were employed instead, moderate 3,4-selectivities were obtained since the opening coordination environment facilitated the 1,4-enchainment (Nd3+: 76.1%; La3+: 62.9%). Replacing AliBu3 by AlEt3, the 5 and 6 systems exhibited high activity and excellent trans-1,4 selectivity for both isoprene (96.5%, 0 °C) and butadiene (92.8%, 20 °C) polymerizations.
Co-reporter:Runhai Chen, Changguang Yao, Meiyan Wang, Hongyan Xie, Chunji Wu, and Dongmei Cui
Organometallics 2015 Volume 34(Issue 2) pp:455-461
Publication Date(Web):January 12, 2015
DOI:10.1021/om500992v
Heterocyclic-fused cyclopentadienyl scandium bis(alkyl) complexes L1–4Sc(CH2SiMe3)2THF ((5-Me-1-Ph-cyclopenta[b]pyrrol-4-yl)Sc(CH2SiMe3)2THF (1), (2,5-Me2-3-Ph-6H-cyclopenta[b]thiophenyl)Sc(CH2SiMe3)2THF (2), (2,4,5,6-Me4-4H-cyclopenta[b]thiophenyl)Sc(CH2SiMe3)2THF (3), (2,3,4,5,6-Me5-4H-cyclopenta[b]thiophenyl)Sc(CH2SiMe3)2THF) (4)) were facilely synthesized by alkane elimination reaction of Sc(CH2SiMe3)3(THF)2 with the heterocyclic-fused cyclopentadienyl ligands HL1–4 in high yields. Complexes 1–4 were characterized by 1H and 13C NMR spectroscopies and X-ray diffraction analyses as THF-solvated monomers, adopting a half-sandwich geometry. Upon activation of [Ph3C][B(C6F5)4]/AliBu3, these half-sandwich scandium complexes displayed various activities toward the copolymerization of ethylene (E) and dicyclopentadiene (DCPD). Complex 1, supported by the phenyl-substituted pyrrole-fused cyclopentadienyl ligand, showed a slightly higher activity than the phenyl-substituted thiophene-fused cyclopentadienyl complex 2. Among the thiophene-fused cyclopentadienyl complexes 2–4, 4, bearing pentamethyl substituents, showed the highest activity of 2.9 × 106 g/molSc·h·bar. The resultant copolymers had adjustable DCPD incorporation varying from 14.0 up to 46.1 mol %, of which the alternating poly(E-alt-DCPD) had a high Tg of 166 °C. In addition, no cross-linking was observed in the copolymers, suggesting that these catalytic systems were highly regioselective for the two active double bonds within DCPD.
Co-reporter:Changguang Yao, Fei Lin, Meiyan Wang, Dongtao Liu, Bo Liu, Na Liu, Zichuan Wang, Shiyu Long, Chunji Wu, and Dongmei Cui
Macromolecules 2015 Volume 48(Issue 7) pp:1999-2005
Publication Date(Web):March 26, 2015
DOI:10.1021/acs.macromol.5b00226
(E)-1-(4-Methylphenyl)-1,3-butadiene (E-1-MPBD) synthesized via the “Wittig-type” reaction was polymerized with the ternary catalytic system (Flu-NHC)Lu(CH2SiMe3)2/AliBu3/[Ph3C][B(C6F5)4] (Flu-NHC = C13H8CH2CH2(NCHCHN(C6H2Me3-2,4,6)C) to afford a new product containing exclusively trans-3,4 (>99%) units with perfect syndiotacticity (rrrr > 99%). The regio-3,4 tacticity was proved by the IR and NMR (1H and 13C) spectroscopic analyses, while the 3,4-stereotacticity was confirmed by a model polymer with lower regularity (3,4 = 90.9%, rrrr = 49.3%) prepared by the binary catalytic system (Am-NHC)Lu(CH2SiMe3)2/[Ph3C][B(C6F5)4] (Am-NHC = 2,6-iPrC6H3N═C(C6H5)NCH2CH2(NCHCHN(C6H2Me3-2,4,6)C). The trans-planar conformation was uncovered through 2D-NOESY and 13C CPMAS NMR technologies. This represents the first stereo 3,4-syndioselective polymerization of 1,3-dienes achieved by a rare-earth metal based catalyst. Moreover, hydrogenating the resulting polymer gave the highly syndiotactic poly(4-methylphenyl-1-butene), which cannot be achieved by any other manner at the present stage.
Co-reporter:Dr. Dongtao Liu;Changguang Yao;Rong Wang;Dr. Meiyan Wang;Zichuan Wang;Dr. Chunji Wu;Fei Lin;Dr. Shihui Li; Xinhua Wan; Dongmei Cui
Angewandte Chemie 2015 Volume 127( Issue 17) pp:5294-5298
Publication Date(Web):
DOI:10.1002/ange.201412166
Abstract
Stereoselective coordination/insertion polymerization of the polar ortho-methoxystyrene has been achieved for the first time by using the cationic β-diketiminato rare-earth-metal species. High activity and excellent isoselectivity (mmmm>99 %) were acheived. The unmasked Lewis-basic methoxy group does not poison the Lewis-acidic metal center, but instead activates the polymerization through σ-π chelation to the active species together with the vinyl group, thus lower the coordination and activation energies as compared with those of styrene derivatives lacking the methoxy group.
Co-reporter:Dr. Dongtao Liu;Changguang Yao;Rong Wang;Dr. Meiyan Wang;Zichuan Wang;Dr. Chunji Wu;Fei Lin;Dr. Shihui Li; Xinhua Wan; Dongmei Cui
Angewandte Chemie International Edition 2015 Volume 54( Issue 17) pp:5205-5209
Publication Date(Web):
DOI:10.1002/anie.201412166
Abstract
Stereoselective coordination/insertion polymerization of the polar ortho-methoxystyrene has been achieved for the first time by using the cationic β-diketiminato rare-earth-metal species. High activity and excellent isoselectivity (mmmm>99 %) were acheived. The unmasked Lewis-basic methoxy group does not poison the Lewis-acidic metal center, but instead activates the polymerization through σ-π chelation to the active species together with the vinyl group, thus lower the coordination and activation energies as compared with those of styrene derivatives lacking the methoxy group.
Co-reporter:Bo Liu;Bao-yu Han;Chun-ling Zhang;Shi-hui Li 李世辉
Chinese Journal of Polymer Science 2015 Volume 33( Issue 5) pp:792-796
Publication Date(Web):2015 May
DOI:10.1007/s10118-015-1629-8
β-imidophosphonamido ligated lutetium alkyl complex (NPNDipp)Lu(CH2SiMe3)2(THF) (NPNDipp = Ph2P(NC6H3iPr2-2,6)2) with the activation of AliBu3 and [Ph3C][B(C6F5)4] exhibited high catalytic activity, medium syndio-(rr = 66%) but remarkably high 3,4-regioselectivity for the polymerization of β-myrcene (MY). In sharp contrast, high isotactic 3,4-polymyrcene (PMY) (mm = 95%) was obtained by the precursor (NPNEt)Lu(CH2SiMe3)2(THF) (NPNEt = PPh2(NC6H3iPr2-2,6)(NC6H4-Et-2)) with less bulky substituents on the N-aryl ring.
Co-reporter:Zehuai Mou, Bo Liu, Meiyan Wang, Hongyan Xie, Ping Li, Lei Li, Shihui Li and Dongmei Cui
Chemical Communications 2014 vol. 50(Issue 77) pp:11411-11414
Publication Date(Web):04 Aug 2014
DOI:10.1039/C4CC05033A
A highly isotactic stereoblock PLA has been obtained using the achiral heteroscorpionate zwitterionic zinc complexes as catalysts, for the first time, via a chain-end control mechanism.
Co-reporter:Bo Liu, Xingbao Wang, Yupeng Pan, Fei Lin, Chunji Wu, Jingping Qu, Yi Luo, and Dongmei Cui
Macromolecules 2014 Volume 47(Issue 24) pp:8524-8530
Publication Date(Web):December 1, 2014
DOI:10.1021/ma5019654
Precisely controlling the stereochemistry of a copolymerization by single catalyst, and achieving copolymers with predicted sequences, is a challenging project in organometallic and macromolecular sciences. This article reports that the copolymerization of isoprene and butadiene with the 3,4- and cis-1,4 different regioselectivities has been accessed through employing a pyridylmethylene functionalized fluorenyl ligated yttrium cationic species. The thus unprecedented regularity combination is attributed mainly to the backbiting interaction of the penultimate unit of the polymer chain to the active central metal ion according to the DFT calculation. Moreover, the compositions can be adjusted by regulating the monomer feed ratio according to the copolymerization kinetics study.
Co-reporter:Bo Liu, Lei Li, Guangping Sun, Jingyao Liu, Meiyan Wang, Shihui Li, and Dongmei Cui
Macromolecules 2014 Volume 47(Issue 15) pp:4971-4978
Publication Date(Web):July 17, 2014
DOI:10.1021/ma501085c
The rare-earth metal complexes bearing NSN-bidentate β-diimidosulfonate ligands (RNSNdipp)Ln(CH2SiMe3)2(THF)n (R = Ph, Ln = Lu (1a), n = 1, Y (1b), n = 2, Sc (1c), n = 1; R = PhNMe2, Ln = Lu (1d), n = 1) were synthesized by treatment of the ion-pairs [Ln(CH2SiMe3)2(THF)x][BPh4] with equimolar amount of the ligand lithium salts (RNSNdipp)Li(THF)2 (NSNdipp = S(NC6H4iPr2-2,6)2). Addition reaction between lutetium tris(alkyl)s, Ln(Z)3(THF)n and NSNdipp gave the corresponding dialkyl complexes (ZNSNdipp)Lu(Z)2(THF)n (Z = CH2SiMe3, n = 1 (1e); Z = o-CH2C6H4NMe2, n = 0 (1f)). Deprotonation of β-imidophosphonamido ligands H–NPNdipp and H–NPNEt (NPNdipp = Ph2P(NC6H3iPr2-2,6)2, NPNEt = PPh2(NC6H3iPr2-2,6)(NC6H4-Et-2)) with Lu(CH2SiMe3)3(THF)2 yielded the corresponding dialkyl complexes (NPNdipp)Lu(CH2SiMe3)2(THF) (2) and (NPNEt)Lu(CH2SiMe3)2(THF) (3). All the complexes had been structurally well-defined, and 1a, 1b, 1e, 2, and 3 were further characterized by X-ray diffraction analysis where the almost planar NSN rare-earth metal unit is Cs (or pseudo Cs) symmetry with the two alkyl groups arranging on both sides and a coordinated THF against it. Upon activation with [PhMe2NH][B(C6F5)4] and AliBu3, all these complexes exhibited high 3,4-regioselectivity (ranging from 91% to >99%) for the polymerization of isoprene. Moreover, the excellent isospecific selectivity up to mmmm > 99% have been achieved with complexes 1 depending on the electronics of the sulfur substituents to give crystalline polyisoprene with the highest Tm (170 °C) reported to date. The NPN-bidentate β-imidophosphonamide ligated rare-earth metal complexes provide both high syndio- and iso- 3,4-selectivities (3,4 > 99%, rr = 66%, mmmm = 96%) depending on the frameworks, steric environment and geometry of the ligands. The regio- and stereo- selective mechanisms proceeded in these systems were explicated by DFT simulation.
Co-reporter:Zehuai Mou, Bo Liu, Xinli Liu, Hongyan Xie, Weifeng Rong, Lei Li, Shihui Li, and Dongmei Cui
Macromolecules 2014 Volume 47(Issue 7) pp:2233-2241
Publication Date(Web):March 27, 2014
DOI:10.1021/ma500209t
A series of oxophosphine (3,5-Me2Pz)2CHP(R)2O (Pz = pyrazole; R = tBu (HL1), Cy (HL2)) and iminophosphine (3,5-Me2Pz)2CHP(R)2NAr (R = Cy, Ar = Ph (HL3); R = Ph, Ar = Ph (HL4), Ar = 2,6-Me2-phenyl (HL5)) heteroscorpionate ligands were synthesized. Abstraction of the methide proton of these ligands by rare-earth-metal tris(alkyl)s, Ln(CH2SiMe3)3(THF)2, afforded the corresponding zwitterionic bis(alkyl) complexes L1–5Ln(CH2SiMe3)2(THF) (L1, Ln = Y (1a), Lu (1b); L2, Ln = Y (2a), Lu (2b); L3, Ln = Y (3a), Lu (3b); L4, Ln = Y (4a), Lu (4b); L5, Ln = Y (5a), Lu (5b), while metathesis reaction of the lithium salts of LiL3 and LiL4 with YCl3(THF)2 or YBr3(THF)2 followed by treatment with LiCH2SiMe3 and KN(SiHMe2)2, respectively, afforded the first heteroscorpionate yttrium mixed halogen/alkyl or amido complexes L3–4Y(Cl)(CH2SiMe3)(THF) (L3 (6a), L4 (7a)), L3–4Y(Cl)(N(SiHMe2)2)(THF) (L3 (8a), L4 (9a)), L4Y(Br)(CH2SiMe3)(THF) (10a), and L4Y(Br)(N(SiHMe2)2)(THF) (11a). The structures of these complexes were well-defined, and the molecular structures of 1a, 2a, 3b, 4b, 5a, and 7a were further characterized by single crystal X-ray diffraction analysis. Complexes 1–5 showed similar high activity toward the ROP of rac-LA at room temperature, and both the alkyl species participated in initiation, of which the lutetium complexes exhibited slightly higher selectivity than their yttrium analogues (Pr = 0.85–0.89 vs 0.80–0.84) despite the bulkiness of the ligands. Interestingly, the mixed halogen complexes 6a–11a were single-site initiators, where the σ-halogen moiety remaining on the central metal showed, for the first time, facilitating the heteroselectivity up to Pr = 0.98. This result sheds new light on designing specifically selective catalytic precursors.
Co-reporter:Lei Li, Bo Liu, Dongtao Liu, Chunji Wu, Shihui Li, Bo Liu, and Dongmei Cui
Organometallics 2014 Volume 33(Issue 22) pp:6474-6480
Publication Date(Web):October 23, 2014
DOI:10.1021/om5008264
A series of aluminum complexes LaAl2Me4 (1), Lb2Al4Me4 (2), and LcAl2Me4 (3) have been prepared from the reaction of AlMe3 with Salan- and Salen-type ligands (LaH2 = [2-OH-3,5-tBu2-C6H2CH2N(CH3)]2-(m-phenylene); LbH4 = [2-OH-3,5-tBu2-C6H2CH2NH]2-(m-phenylene); LcH2 = [2-OH-3,5-tBu2-C6H2CH═N]2-(m-phenylene)), respectively. All these complexes were characterized by NMR spectroscopy, X-ray diffraction, and elemental analyses, with complexes 1 and 3 adopting binuclear structures, while complex 2 being tetranuclear. In the presence of alcohol, the binuclear complexes 1 and 3 catalyzed controlled ring-opening homopolymerizations of both ε-CL and l-LA. In the copolymerization experiments, complexes 1 and 2 produced tapered copolymers of ε-CL and l-LA, while complex 3 was able to provide ε-CL-co-l-LA with tendentially random structure indicated by the average lengths of the caproyl and lactidyl sequences (LCL = 1.4; LLA = 2.6). Particularly, addition of excess alcohol into the catalytic system of complex 3 established the first “immortal” copolymerization of ε-CL/l-LA, which accelerated the polymerization rates of both monomers and, thus, afforded random copolymers with predictable molecular weights and narrow molecular weight distributions.
Co-reporter:Changguang Yao, Dongtao Liu, Ping Li, Chunji Wu, Shihui Li, Bo Liu, and Dongmei Cui
Organometallics 2014 Volume 33(Issue 3) pp:684-691
Publication Date(Web):January 24, 2014
DOI:10.1021/om400925a
The amidino-modified N-heterocyclic carbene ligated lutetium bis(alkyl) complex 1, (Am-NHC)Lu(CH2SiMe3)2, was synthesized by treatment of (AmH-NHC-H)Br ((2,6-iPrC6H3N═C(C6H5)NHCH2CH2(NCHCHN(C6H2Me3-2,4,6)CH)Br) with ((trimethylsilyl)methyl)lithium (LiCH2SiMe3) and lutetium tris(alkyls) (Lu(CH2SiMe3)3(THF)2) via double-deprotonation reactions and characterized by NMR spectroscopy and X-ray diffraction analysis. Under activation of an organoborate, complex 1 exhibited distinguished catalytic performance for the polymerization of isoprene with respect to high activity, 3,4-regioselectivity (99.3%), and livingness mode. In contrast to the systems reported to date, this system seemed not to be affected obviously by the polymerization temperature (0–80 °C), solvents, monomer-to-initiator ratios (500–5000), and type of organoborate. The resultant polymers have high glass-transition temperatures (38–48 °C) and moderate syndiotacticity (racemic enchainment triad rr 45%, pentad rrrr 20%). In addition, the living lutetium–polyisoprene active species could further initiate the ring-opening polymerization of ε-caprolactone to give selectively the poly(3,4-isoprene)-b-polycaprolactone block copolymers with controllable molecular weight (from 4.9 × 104 to 10.2 × 104) and narrow polydispersity.
Co-reporter:Hongyan Xie, Zehuai Mou, Bo Liu, Ping Li, Weifeng Rong, Shihui Li, and Dongmei Cui
Organometallics 2014 Volume 33(Issue 3) pp:722-730
Publication Date(Web):January 28, 2014
DOI:10.1021/om401056s
Alkane elimination reactions of phosphinimino-amine ligands HL1–8 ((2,6-Me2-C6H3NH)C(Ph)═CHPPh2(NAr) (Ar = C6H5 (HL1); 2,6-Me2-C6H3 (HL2); 2,6-Et2-C6H3 (HL3); 2,6-iPr2-C6H3 (HL4); 2-OMe-C6H4 (HL5); 2-Cl-C6H4 (HL6); 3-CF3-C6H4 (HL7); 4-MeO-C6H4 (HL8)) with MgnBu2, respectively, afforded a series of phosphinimino-amine-based complexes L1–8MgnBu(THF) (1–8) by releasing butane. Complexes 1–8 are phosphinimino-amine-ligated THF-solvated mono(alkyl)s, among which 1–4 adopt twisted tetrahedral geometries, whereas 5 contains a trigonal bipyramido geometry core. Complexes 1–8 all display high activity for the ring-opening polymerization of rac-lactide. The molecular weights of the resulting PLA are close to the theoretic values, and the molecular weight distributions are narrow. Moreover, these complexes show medium to high heteroselectivity, which, interestingly, increases with the decrease of the ligand steric hindrance; thus, complex 1, bearing a less bulky ligand, exhibits a heteroselectivity of Pr = 0.98, the highest value of a magnesium-based initiator achieved to date. The kinetics study showed that the polymerization rate is first-order dependent on both monomer and initiator concentrations, and the overall rate equation is −d[LA]/dt = 3.78 M–1 s–1 [LA][Mg].
Co-reporter:Dr. Shihui Li;Dr. Meiyan Wang;Bo Liu;Lei Li; Jianhua Cheng;Dr. Chunji Wu;Dr. Dongtao Liu;Dr. Jingyao Liu;Dr. Dongmei Cui
Chemistry - A European Journal 2014 Volume 20( Issue 47) pp:15493-15498
Publication Date(Web):
DOI:10.1002/chem.201404809
Abstract
The first four-coordinate methanediide/alkyl lutetium complex (BODDI)Lu2(CH2SiMe3)2(μ2-CHSiMe3)(THF)2 (BODDI=ArNC(Me)CHCOCHC(Me)NAr, Ar=2,6-iPr2C6H3) (1) was synthesized by a thermolysis methodology through α-H abstraction from a Lu–CH2SiMe3 group. Complex 1 reacted with equimolar 2,6-iPrC6H3NH2 and Ph2CO to give the corresponding lutetium bridging imido and oxo complexes (BODDI)Lu2(CH2SiMe3)2(μ2-N-2,6-iPr2C6H3)(THF)2 (2) and (BODDI)Lu2(CH2SiMe3)2(μ2-O)(THF)2 (3). Treatment of 3 with Ph2CO (4 equiv) caused a rare insertion of Lu–μ2-O bond into the CO group to afford a diphenylmethyl diolate complex 4. Reaction of 1 with PhN=CO (2 equiv) led to the migration of SiMe3 to the amido nitrogen atom to give complex (BODDI)Lu2(CH2SiMe3)2-μ-{PhNC(O)CHC(O)NPh(SiMe3)-κ3N,O,O}(THF) (5). Reaction of 1 with tBuNC formed an unprecedented product (BODDI)Lu2(CH2SiMe3){μ2-[η2:η2-tBuNC(=CH2)SiMe2CHCNtBu-κ1N]}(tBuNC)2 (6) through a cascade reaction of NC bond insertion, sequential cyclometalative γ-(sp3)-H activation, CC bond formation, and rearrangement of the newly formed carbene intermediate. The possible mechanistic pathways between 1, PhNCO, and tBuNC were elucidated by DFT calculations.
Co-reporter:Weifeng Rong ; Jianhua Cheng ; Zehuai Mou ; Hongyan Xie
Organometallics 2013 Volume 32(Issue 19) pp:5523-5529
Publication Date(Web):September 26, 2013
DOI:10.1021/om400803q
The scandium bis(alkyl) complex bearing the phosphazene ligand L1Sc(CH2SiMe3)2 (1) (L1 = N(PPh2═NPh)2) reacted with an equimolar amount of 2,6-diisopropylaniline to afford the corresponding mixed alkyl/anilido complex L1Sc[NHC6H3(iPr)2](CH2SiMe3) (2). Under mild conditions (20 °C, 4 h or 0 °C, 12 h), complex 2 could be swiftly transformed to the terminal imido complex L1Sc═N[C6H3(iPr)2](DMAP)2 (4) in the presence of DMAP (DMAP = 4-N,N-dimethylaminopyridine). Correspondingly, treatment of the yttrium and lutetium bis(alkyl) complexes L2Ln(CH2SiMe3)2 (L2 = N[Ph2PNC6H3(iPr)2]2; Ln = Y (7), Lu (8)) with equimolar amounts of 2,6-diisopropylaniline gave the mixed alkyl/anilido complexes L2Ln[NHC6H3(iPr)2](CH2SiMe3) (Ln = Y (9), Lu (10)), which, however, underwent dealkylation of the Ln–CH2SiMe3 species at temperatures of 60 °C for 9 and 100 °C for 10 to afford bis(anilido) complexes L2Ln[NHC6H3(iPr)2]2 (Ln = Y (11), Lu (12)) as redistribution products. All these complexes have been characterized by 1H, 13C{1H}, and 31P{1H} NMR spectroscopy and X-ray diffraction analyses, and clear structural insight into the behavior of an imido functionality on a lanthanide metal center was provided.
Co-reporter:Zehuai Mou, Bo Liu, Meiyan Wang, Hongyan Xie, Ping Li, Lei Li, Shihui Li and Dongmei Cui
Chemical Communications 2014 - vol. 50(Issue 77) pp:NaN11414-11414
Publication Date(Web):2014/08/04
DOI:10.1039/C4CC05033A
A highly isotactic stereoblock PLA has been obtained using the achiral heteroscorpionate zwitterionic zinc complexes as catalysts, for the first time, via a chain-end control mechanism.
Co-reporter:Bo Liu, Lei Li, Guangping Sun, Dongtao Liu, Shihui Li and Dongmei Cui
Chemical Communications 2015 - vol. 51(Issue 6) pp:NaN1041-1041
Publication Date(Web):2014/11/21
DOI:10.1039/C4CC08962F
The polymerization of bio-renewable myrcene (MY), using a cationic β-diimidosulfonate lutetium catalyst in high activity, afforded an unprecedented isotactic 3,4-polymyrcene (PMY) with a low Tg (−42 °C). Based on this result, the random and block copolymerization of myrcene and isoprene (IP) resulted in novel elastomers that comprise the amorphous iso-3,4-PMY and iso-3,4-PIP sequences.
Co-reporter:Dongtao Liu, Rong Wang, Meiyan Wang, Chunji Wu, Zichuan Wang, Changguang Yao, Bo Liu, Xinhua Wan and Dongmei Cui
Chemical Communications 2015 - vol. 51(Issue 22) pp:NaN4688-4688
Publication Date(Web):2015/02/06
DOI:10.1039/C5CC00470E
Unprecedented coordination–insertion polymerizations of polar methoxyl substituted styrene derivatives, in despite of the position of the substituent, have been achieved using a pyridyl methylene fluorenyl yttrium bis(alkyl) precursor with high activity to give polar polystyrenes of high molecular weight and perfect syndiotacticity.
Co-reporter:Weifeng Rong, Dongliang He, Meiyan Wang, Zehuai Mou, Jianhua Cheng, Changguang Yao, Shihui Li, Alexander A. Trifonov, Dmitrii M. Lyubov and Dongmei Cui
Chemical Communications 2015 - vol. 51(Issue 24) pp:NaN5065-5065
Publication Date(Web):2015/02/11
DOI:10.1039/C4CC07262F
The first neutral rare-earth metal dinuclear dihydrido complexes [(NPNPN)LnH2]2 (2-Ln; Ln = Y, Lu; NPNPN: N[Ph2PNC6H3(iPr)2]2) bearing μ2-bridging hydride ligands have been synthesized. In the presence of THF, 2-Y undergoes intramolecular activation of the sp2 C–H bond to form dinuclear aryl–hydride complex 3-Y containing three μ2-bridging hydride ligands.
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