文献类型：期刊文献

英文题名：Magnesium and Calcium Complexes Containing Biphenyl-Based Tridentate Iminophenolate Ligands for Ring-Opening Polymerization of rac-Lactide

作者：Yi, Wei;Ma, Haiyan[1]

机构：[1]E China Univ Sci & Technol, Shanghai Key Lab Funct Mat Chem, Shanghai 200237, Peoples R China; E China Univ Sci & Technol, Lab Organometall Chem, Shanghai 200237, Peoples R China

年份：2013

卷号：52

期号：20

起止页码：11821

外文期刊名：INORGANIC CHEMISTRY

收录：;WOS:【SCI-EXPANDED(收录号:WOS:000326065600019)】；

基金：This work is subsidized by the National Natural Science Foundation of China (Grant 21074032), the Program for New Century Excellent Talents in University (Grant NCET-06-0413 to H.M.), and the Fundamental Research Funds for the Central Universities (Grants WD1113011 and WK1214048). All financial support is gratefully acknowledged. H.M. also is thankful for the very kind donation of a Braun glovebox by the AvH Foundation.

语种：英文

摘要：A series of racemic 2-[(2'-methoxybiphenyl-2-ylimino)methyl]-4-R-2-6-R-1-phenols ((LH)-H-1-(LH)-H-8) were reacted with {Mg[N(SiMe3)(2)](2)}(2) and Ca[N(SiMe3)(2)](2)center dot 2THF (THF = tetrahydrofuran), respectively, to provide nine heteroleptic magnesium complexes L1-8MgN(SiMe3)(2) [R-1 = P-i(r), R-2 = H (1a); = Bu-t, R-2 = Me (2a and 2a center dot THF); R-1 = R-2 = Bu-t (3a); R-1 = R-2 = CMe2Ph (4a); R-1 = CPh3, R-2 = Bu-t (5a); R-1 = 1-piperidinylmethyl, R-2 = Bu-t (6a); R-1 = Cl, R-2 = Bu-t (7a); R-1 = Br, R-2 = Bu-t (8a)], two homoleptic calcium complexes (L-2,L-5)(2)Ca (2b and 5b), and one heteroleptic calcium complex [(L-4)CaN(SiMe3)(2)center dot THF] (4b), which have been fully characterized. In the solid state, magnesium complexes 2a and 6a are isostructural, and each possesses a monomeric structure, while magnesium complexes 7a and 8a are dimeric, where the two metal centers are bridged by two phenolate oxygen atoms of the ligands. The coordination geometry around the magnesium center in these complexes can be best described as a distorted tetrahedral geometry. Although bearing the same iminophenoloate ligand, the molecular structures of complexes 2a and 2a center dot THF are different from each other. In complex 2a center dot THF, the coordination of one molecule of THF to the magnesium atom leads to dissociation of the methoxy group of the ligand from the metal center. The homoleptic calcium complex 2b has a six-coordinate metal core ligated by all six donor atoms of two iminophenolate ligands. The heteroleptic magnesium complexes 1a-8a and calcium complex 4b proved to be efficient initiators for the ring-opening polymerization of rac-lactide at ambient temperature in THF or at 70 degrees C in toluene, and the polymerizations were better controlled in the presence of 2-propanol. The introduction of a bulky ortho substituent on the phenoxy unit of the ligand resulted in an increase of the catalytic activity of the corresponding metal complex. Microstructure analysis of the resultant poly(rac-lactide) samples via homonuclear-decoupled H-1 NMR spectroscopy revealed P-r values ranging from 0.60 to 0.81, which closely depended on the employed catalyst and polymerization conditions.