Mingqiang Xue

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Name: 薛明强; MingQiang Xue

Organization: Soochow University , China

Department: Department of Chemistry

Title: Professor(PhD)

TOPICS

Organic Chemistry

Chemicals
References

Catalytic addition of amines to carbodiimides by bis(β-diketiminate)lanthanide(II) complexes and mechanistic studies

Co-reporter:Mingqiang Xue, Yu Zheng, Yubiao Hong, Yingming Yao, Fan Xu, Yong Zhang and Qi Shen

Dalton Transactions 2015 vol. 44(Issue 46) pp:20075-20086

Publication Date(Web):20 Oct 2015

DOI:10.1039/C5DT03674G

Reduction reactions of bis(β-diketiminate)lanthanide(III) chlorides formed in situ by reactions of anhydrous LnCl3 with 2 equiv. of sodium salt of the β-diketiminate ligand in THF with a Na/K alloy afforded a series of bis(β-diketiminate)lanthanide(II) complexes LnL2(THF)n (L = L2,6-Me2 = [N(2,6-Me2C6H3)C(Me)]2CH−, n = 1, Ln = Eu (1); L = L2,4,6-Me3 = [N(2,4,6-Me3C6H2)C(Me)]2CH−, n = 1, Ln = Eu (2); L = L2,6-iPr2 = [N(2,6-iPr2C6H3)C(Me)]2CH−, n = 0, Ln = Eu (3), Sm (4); L = L2,6-ipr2Ph = [(2,6-iPr2C6H3)NC(Me)CHC(Me)N(C6H5)]−, n = 0, Ln = Eu (5), Yb (6); L = L2-Me = [N(2-MeC6H4)C(Me)]2CH−, n = 1, Ln = Yb (7)) in high yields. All the complexes, especially the complexes of SmII (4) and EuII (5), were found to be excellent pre-catalysts for catalytic addition of amines to carbodiimides to multi-substituted guanidines with a wide scope of substrates. The activity depends both on the central metals and the ligands with the active sequence of YbII < EuII and EuII < SmII and L2,6-Me2 < L2,4,6-Me3 ∼ L2,6-iPr2 < L2,6-ipr2Ph for the ligands. The mechanistic study by the isolation of guanidinate species and their reactivity revealed that EuII monoguanidinate complexes Eu(L2,6-Me2)[(C6H5N)C(NHCy)(NCy)](DME) (8) and Eu(L2,6-ipr2Ph)[(C6H5N)C(NHCy)(NCy)](THF)2 (9) should be the key active intermediates for the systems with EuII complexes and a YbIII bis(guanidinate) complex Yb(L2-Me)[(C6H5N)C(NHCy)(NCy)]2 (11) for the system using a YbII complex.

Bis(-diketiminato) lanthanide amides: synthesis, structure and catalysis for the polymerization of l-lactide and -caprolactone

Co-reporter:Yu Zheng;Rui Jiao;Xiao-dong Shen;Ming-qiang Xue;Ying-ming Yao;Yong Zhang ;Qi Shen

Applied Organometallic Chemistry 2014 Volume 28( Issue 6) pp:

Publication Date(Web):

DOI:10.1002/aoc.3150

Treatment of the chlorides (L^2,6-iPr2_Ph)₂LnCl (L^2,6-iPr2_Ph = [(2,6-ⁱPr₂C₆H₃)NC(Me)CHC(Me)N(C₆H₅)]⁻) with 1 equiv. of NaNH(2,6-ⁱPr₂C₆H₃) afforded the monoamides (L^2,6-iPr2_Ph)₂LnNH(2,6-ⁱPr₂C₆H₃) (Ln = Y (1), Yb (2)) in good yields. Anhydrous LnCl₃ reacted with 2 equiv. of NaL^2,6-iPr2_Ph in THF, followed by treatment with 1 equiv. of NaNH(2,6-ⁱPr₂C₆H₃), giving the analogues (L^2,6-iPr2_Ph)₂LnNH(2,6-ⁱPr₂C₆H₃) (Ln = Sm (3), Nd (4)). Two monoamido complexes stabilized by two L^2-Me ligands, (L^2-Me)₂LnNH(2,6-ⁱPr₂C₆H₃) (L^2-Me = [N(2-MeC₆H₄)C(Me)]₂CH)⁻; Ln = Y (5), Yb (6)), were also synthesized by the latter route. Complexes 1, 2, 3, 4, 5, 6 were fully characterized, including X-ray crystal structure analyses. Complexes 1, 2, 3, 4, 5, 6 are isostructural. The central metal in each complex is ligated by two β-diketiminato ligands and one amido group in a distorted trigonal bipyramid. All the complexes were found to be highly active in the ring-opening polymerization of L-lactide (L-LA) and ε-caprolactone (ε-CL) to give polymers with relatively narrow molar mass distributions. The activity depends on both the central metal and the ligand (Yb < Y < Sm ≈ Nd and L^2-Me < L^2,6-iPr2_Ph). Remarkably, the binary 3/benzyl alcohol (BnOH) system exhibited a striking ‘immortal’ nature and proved able to quantitatively convert 5000 equiv. of L-LA with up to 100 equiv. of BnOH per metal initiator. All the resulting PLAs showed monomodal, narrow distributions (M_w/M_n = 1.06 − 1.08), with molar mass (M_n) decreasing proportionally with an increasing amount of BnOH. The binary 4/BnOH system also exhibited an ‘immortal’ nature in the polymerization of ε-CL in toluene. Copyright © 2014 John Wiley & Sons, Ltd.

Unprecedented reaction of bridged bis(guanidinate) lanthanide complexes: sterically induced deprotonation

Co-reporter:Chuanyong Wang, Xingmin Zhang, Mingqiang Xue, Yong Zhang and Qi Shen

Dalton Transactions 2013 vol. 42(Issue 19) pp:7009-7018

Publication Date(Web):22 Feb 2013

DOI:10.1039/C3DT32882A

Reaction of LnCl3 with a lithium salt of bridged bis(guanidinate) bearing a rigid naphthalene linker [Li2{LH2}2Li2] (LH2 = 1,8-C10H6{NC(NiPr)(NHiPr)}2) (1), which was synthesized by the reaction of 1,8-diaminonaphthalene with 2 equiv. of nBuLi, followed by treatment with 2 equiv. of N,N′-diisopropylcarbodiimide, yielded the chlorides [LnCl{LH2}] (Ln = Yb (2), Y (3)) in good yields. Metathesis reaction of 2 and 3 with NaN(SiMe3)2 did not afford the corresponding amide complexes, but the deprotonation products of [Ln{LH}]2 (LH = 1,8-C10H6{NC(NiPr)(NHiPr)}{NC(NiPr)2}; Ln = Yb (4), Y (5)) were isolated instead. The LH in 4 and 5 both act as a bridging ligand binding to two metals in a μ–η1:η2:η2 fashion, and the re-arrangement of LH occurred during the reaction. The size of the amido group was found to have a great influence on the outcome of the metathesis reaction. Reaction of 2 with bulky NaNH(C6H3iPr2-2,6) afforded 4 as the only product, whereas the same reaction with less bulky LiNH(C6H4Cl-4) and LiNH(C6H4CH3-4) led to the corresponding amides, [Yb{LH2}(NHC6H4Cl-4)]2 (6) and [Yb{LH2}(NHC6H4CH3-4)]2 (7), respectively. The re-arrangement of ligands was also observed in both cases. A possible pathway for the deprotonation of LH2 was discussed. Molecular structures of 1–7 were determined by X-ray single crystal analysis.

Bridged bis(amidinate) lanthanide aryloxides: syntheses, structures, and catalytic activity for addition of amines to carbodiimides

Co-reporter:Jing Tu, Wenbo Li, Mingqiang Xue, Yong Zhang and Qi Shen

Dalton Transactions 2013 vol. 42(Issue 16) pp:5890-5901

Publication Date(Web):04 Feb 2013

DOI:10.1039/C3DT33069A

Various lanthanide aryloxide complexes supported by bridged bis(amidinate) ligand L, LLnOAr(DME) (L = Me3SiNC(Ph)N(CH2)3NC(Ph)NSiMe3, DME = dimethoxyethane, Ln = Y, Ar = 2,6-(Me)2C6H3 (1), 2,6-(iPr)2C6H3 (2), 2,6-(tBu)2-4-(Me)C6H2 (3); Ar = 2,6-(tBu)2-4-(Me)C6H2, Ln = Nd (4), Sm (5), Yb (6)) were synthesized, and complexes 1, 2 and 4–6 were characterized by single crystal X-ray diffraction. All the complexes are efficient precatalysts for catalytic addition of amines to carbodiimides. The catalytic activity is influenced by lanthanide metals and the aryloxide groups (Nd (4) ∼ Sm (5) < Y (3) ∼ Yb (6) and -2,6-(Me)2C6H3 < -2,6-(iPr)2C6H3 < -2,6-(tBu)2-4-(Me)C6H2). The catalytic addition reaction with 3 showed a good scope of substrates. The mechanism investigation revealed the real active intermediate being the monoguanidinate complexes supported by an aryloxide and an amidine-functionalized amidinate group, L′Ln[O2,6-(tBu)2-4-(Me)C6H2][RNCNHRN(Ar′)] (L′ = Me3SiNHC(Ph)N(CH2)3NC(Ph)NSiMe3, R = iPr, Ar′ = phenyl, Ln = Yb (8), Y (11); R = Cy, Ar′ = phenyl, Ln = Yb (10), Y (12); R = iPr, Ar′ = 4-ClC6H4, Ln = Yb (9)), which were isolated from the reactions of 6 (or 3) with amine and carbodiimide in a molar ratio of 1:1:1 and structurally characterized. The Ln-active group in the present precatalyst is a Ln–amidinate species, not the Ln–OAr group.

-Diketiminatoytterbium aryloxides: synthesis, structural characterization, and catalytic activity for addition of amines to carbodiimides

Co-reporter:Ling-xia Cai;Ying-ming Yao;Ming-qiang Xue;Yong Zhang ;Qi Shen

Applied Organometallic Chemistry 2013 Volume 27( Issue 6) pp:366-372

Publication Date(Web):

DOI:10.1002/aoc.2996

The steric effect of an aryloxido group on the synthesis and molecular structures of ytterbium aryloxides supported by β-diketiminato ligand L (L = [N(2,6-Me₂C₆H₃)C(Me)]₂CH⁻) is reported. Reactions of β-diketiminatoytterbium dichloride, LYbCl₂(THF)₂, with NaOAr¹ in THF (Ar¹ = [2,6-^tBu₂-4-MeC₆H₂], THF = tetrahydrofuran) at 60°C gave the corresponding ytterbium complexes LYb(OAr¹)Cl(THF) (1) and LYb(OAr¹)₂ (1), depending on the molar ratio of dichloride to sodium aryloxide, respectively, while the same reactions with NaOAr² and NaOAr³ (Ar² = [2,6-ⁱPr₂C₆H₃], Ar³ = [2,6-Me₂C₆H₃]) in 1:1 or 1:2 molar ratio in THF afforded only bisaryloxide complexes LYb(OAr²)₂(THF) (1) and LYb(OAr³)₂(THF) (4) in good yields, respectively. Complexes 1, 2, 3, 4 were fully characterized, including X-ray crystal structure analyses. All the complexes are efficient pre-catalysts for the catalytic addition of amines to carbodiimides giving guanidines. Copyright © 2013 John Wiley & Sons, Ltd.

Synthesis of a Naphthalene-Bridged Bis(guanidinato)ytterbium(II) Complex and an Unexpected Pathway in Its Reaction with CH3CN, p-ClC6H4CH2CN, and Ph2CHCN

Co-reporter:Chuanyong Wang, Xingmin Zhang, Mingqiang Xue, Yong Zhang, and Qi Shen

Organometallics 2013 Volume 32(Issue 13) pp:3618-3624

Publication Date(Web):June 21, 2013

DOI:10.1021/om400200f

A novel binuclear ytterbium(II) complex supported by a naphthalene-bridged bis(guanidinate) ligand, [Yb(μ-L)(THF)]2 (1; L = 1,8-C10H6{NC(NiPr)(NHiPr)}2), was synthesized by the reduction reaction of [Yb(L)Cl(THF)2] with Na/K alloy in THF and structurally characterized. The reactions of 1 with CH3CN and p-ClC6H4CH2CN resulted in the formation of the corresponding binuclear (crotononitrileamido)ytterbium(III) complexes [Yb(L)(μ(N,N′)-N(H)C(Me)═C(H)C≡N)(THF)]2 (2) and [Yb(L)(μ(N,N′)-N(H)C(CH2C6H4-p-Cl)═C(C6H4-p-Cl)C≡N)(THF)]2 (3) via metalation of the nitrile, followed by insertion of a second nitrile molecule. Treatment of 1 with the bulkier Ph2CHCN afforded the mononuclear (keteniminato)ytterbium(III) complex [Yb(L)(N═C═CPh2)(THF)2] (4) by deprotonation of Ph2CHCN. The molecular structures of 2–4 have been determined.

Bridged bis(amidinate) lanthanide aryloxides: syntheses, structures, and catalytic activity for addition of amines to carbodiimides

Co-reporter:Jing Tu, Wenbo Li, Mingqiang Xue, Yong Zhang and Qi Shen

Dalton Transactions 2013 - vol. 42(Issue 16) pp:NaN5901-5901

Publication Date(Web):2013/02/04