Homden Damien M, Redshaw Carl, Hughes David L
School of Chemical Sciences and Pharmacy, University of East Anglia, Earlham Road, Norwich, Norfolk NR4 7TJ, UK.
Inorg Chem. 2007 Dec 10;46(25):10827-39. doi: 10.1021/ic701461b. Epub 2007 Nov 9.
The family of ligands containing an N2O2S2 core, namely, 1,2-di(3-Me-5-t-Bu-salicylaldimino-o-phenylthio)ethane (H2L1), 1,3-di(3-Me-5-t-Bu-salicylaldimino-o-phenylthio)propane (H2L2), 1,4-di(3-Me-5-t-Bu-salicylaldimino-o-phenylthio)butane (H2L3), and 1,2-di(3-Me-5-t-Bu-salicylaldamino-o-phenylthio)ethane (H2L4), have been prepared and complexed with a variety of vanadium chlorides and alkoxides to afford complexes of the form [V(X)L1] (X = O (1), Np-tol (2), Cl (3)), [V(O)(L2,3)] (L2 (4), L3 (5)), and [V(L4)] (6). Crystal structure determinations of H2L1 and H2L4 show the molecule to be centrosymmetric about the bridging ethane moiety, with structural determination of 1 and 3 revealing isostructural monomeric complexes in which the ligand chelates in such a way as to afford pseudo-octahedral coordination at the vanadium center. Prolonged reaction of H2L1 with [V(Np-tol)(OEt)3] led, via oxidative cleavage of the C-S bond, to the bimetallic complex [V2L1(3-Me,5-t-Bu-salicylaldimino-o-phenylthiolate)2] [VL'] (7), as characterized by single-crystal X-ray crystallography. 7 was also isolated from the reaction of H2L4 and [VO(On-Pr)3]. The ability of 1-7 to catalyze the homopolymerization of ethylene and the copolymerization of ethylene/1-hexene in the presence of dimethylaluminum chloride (DMAC) has been assessed: screening reveals that for ethylene homopolymerization 1-7 are all highly active (>1000 g/mmol.h.bar), with the highest activity (ca. 11 000 g/mmol.h.bar) observed using catalyst 3; the use of trimethyl aluminum (TMA) or methylaluminoxane (MAO) as the cocatalyst led only to poorly active systems producing negligible polymer. Analysis of the polyethylene produced showed high molecular weight linear polymers with narrow polydispersities. For ethylene/1-hexene copolymerization, activities as high as 1,190 g/mmol.h.bar were achieved (4); analysis of the copolymer indicated an incorporation of 1-hexene in the range of 5-13%.
含有N2O2S2核心的配体家族，即1,2 - 二(3 - 甲基 - 5 - 叔丁基 - 水杨醛亚氨基 - 邻苯硫基)乙烷(H2L1)、1,3 - 二(3 - 甲基 - 5 - 叔丁基 - 水杨醛亚氨基 - 邻苯硫基)丙烷(H2L2)、1,4 - 二(3 - 甲基 - 5 - 叔丁基 - 水杨醛亚氨基 - 邻苯硫基)丁烷(H2L3)和1,2 - 二(3 - 甲基 - 5 - 叔丁基 - 水杨醛氨基 - 邻苯硫基)乙烷(H2L4)，已被制备并与多种钒的氯化物和醇盐络合，得到形式为[V(X)L1](X = O (1)、Np - 甲苯基(2)、Cl (3))、[V(O)(L2,3)](L2 (4)、L3 (5))和V(L4)的配合物。H2L1和H2L4的晶体结构测定表明分子关于桥连乙烷部分呈中心对称，1和3的结构测定揭示了同构的单体配合物，其中配体以这样一种方式螯合，即在钒中心提供假八面体配位。H2L1与[V(Np - 甲苯基)(OEt)3]的长时间反应通过C - S键的氧化裂解导致双金属配合物[V2L1(3 - 甲基,5 - 叔丁基 - 水杨醛亚氨基 - 邻苯硫醇盐)2]VL'，通过单晶X射线晶体学表征。7也从H2L4与[VO(On - Pr)3]的反应中分离得到。评估了1 - 7在二甲基氯化铝(DMAC)存在下催化乙烯均聚和乙烯/1 - 己烯共聚的能力：筛选表明对于乙烯均聚，1 - 7都具有高活性(>1000 g/mmol·h·bar)，使用催化剂3观察到最高活性(约11000 g/mmol·h·bar)；使用三甲基铝(TMA)或甲基铝氧烷(MAO)作为助催化剂仅导致活性很差的体系，产生的聚合物可忽略不计。对所生产的聚乙烯的分析表明是具有窄多分散性的高分子量线性聚合物。对于乙烯/1 - 己烯共聚，实现了高达1190 g/mmol·h·bar的活性(4)；对共聚物的分析表明1 - 己烯的掺入量在5 - 13%范围内。
