A Family of 1,1,3,3‐Tetraalkylguanidine (H‐TAG) Solvated Zinc Aryloxide Precatalysts for the Ring‐Opening Polymerization of
rac
‐Lactide
摘要:
AbstractReaction of [Zn(μ‐TAG){N(SiMe3)2}]2 {TAG = N=C[N(CH2CH3)2N(CH3)2] (DEDMG), N=C{[NCH2CH2CH2CdH2(N–Cd)]N(CH2CH3)2} (DEPYRG) and N=C{[NCH2CH2CH2CH2CeH2(N–Ce)]N(CH2CH3)2} (DEPIPG)} with 2 equiv. of ethanol (EtOH) and 2 equiv. of HOAr {OAr = OC6H3(CMe3)‐2‐(CH3)‐6 (BMP) or OC6H2[C(CH3)3]2‐2,6‐(CH3)‐4 (4MeDBP)} results in dizinc alkoxides with the general formula [Zn(μ‐OEt)(OAr)(H‐TAG)]2 (1–3). Et2Zn was additionally treated with 2 equiv. of 1,1,3,3‐tetramethylguanidine (H‐TMG) and H‐BMP or HOC6H3(C6H5)2‐2,6 to yield [Zn(BMP)2(H‐TMG)2] (4) and [Zn{OC6H3(C6H5)2‐2,6}2(H‐TMG)2] (5). Complexes 1, 2, 4, and 5 were characterized by single‐crystal X‐ray diffraction. Polymerization of rac‐lactide with 1–5 and [Zn(μ‐OMe)(4MeDBP)(H‐TMG)]2 (6) were found to generate polylactide (PLA). The bulk powders for all complexes were found to be in agreement with the crystal structures based on elemental analyses, FTIR spectroscopy, and 1H and 13C NMR spectroscopic studies.
Synthesis and characterization of a series of zinc complexes stabilized by 1,1,3,3-tetraalkylguanidinate (TAG) ligands: [Zn(μ-TAG){N(SiMe3)2}]2
摘要:
A series of novel structurally varied low-coordinate zinc complexes utilizing 1,1,3,3-tetraalkylguanidinate (TAG) ligands were synthesized and characterized. Li(TAG) and lithium bis-trimethylsilylamide, LiN(SiMe3)(2), were successfully reacted with ZnCl2 in a 1:1 ratio to yield the corresponding dinuclear complexes with the general formula [Zn(mu-TAG) {N(SiMe3)(2)}](2), where[GRAPHICS]and[GRAPHICS]Compounds 1-6 were characterized by single-crystal X-ray diffraction. The bulk powders for all complexes were found to be in agreement with the crystal structures based on elemental analyses, FT-IR spectroscopy, and H-1 and C-13 NMR studies. (C) 2007 Elsevier Ltd. All rights reserved.