Vanadium-Based Pro-Catalysts Bearing Depleted 1,3-Calix[4]arenes for Ethylene or ε-Caprolactone Polymerization

Reaction of [V(X)(OR)3] (X = O, Np-tolyl, R = nPr, tBu) with 5,11,17,23-tBu-25,27-dihydroxycalix[4]arene (LH2) led to the formation of [V(X)(OR)L]2 X = O, R = nPr (1); X = Np-tolyl, R = nPr (2); X = Np-tolyl, R = tBu (3) as the major product. In the case of X = O, the minor hydrolysis product {[VO(OnPr)]2(μ-O)L}2 (4) has also been characterized. Complexes (1)–(4), in the presence of the co-catalyst dimethylaluminum chloride and the reactivator ethyltrichloroacetate, are highly active (≤16,400 g/mmol h bar), thermally stable pro-catalysts for the polymerization of ethylene. The use of silica supports with (1) and (2) under slurry conditions yielded polymer with activities ≤30 g/mmol h. Complexes (1)–(3) have also been screened as pro-catalysts for the ring-opening polymerization of ε-caprolactone; the conversion rate order (1) (94%) > (2) (46%) > (3) (20%) was observed at 80 °C over 72 h.

将[V(X)(OR)₃]（X=O、N-对甲苯基，R=正丙基（nPr）、叔丁基（tBu））与5,11,17,23-叔丁基-25,27-二羟基杯[4]芳烃（LH₂）发生反应，主要生成[V(X)(OR)L]₂型产物，其中X=O、R=nPr时对应产物1；X=N-对甲苯基、R=nPr时对应产物2；X=N-对甲苯基、R=tBu时对应产物3。当X为O时，次要水解产物{[VO(OⁿPr)]₂(μ-O)L}₂（产物4）也得到了结构表征。化合物1~4在助催化剂二甲基氯化铝与活化剂三氯乙酸乙酯存在下，是活性可达≤16400 g/mmol·h·bar的热稳定乙烯聚合前催化剂。采用二氧化硅载体负载化合物1和2、在淤浆工艺条件下进行聚合时，所得聚合物的活性≤30 g/mmol·h。化合物1~3还被筛选为ε-己内酯开环聚合的前催化剂，在80℃下反应72小时后，单体转化率顺序为(1)（94%）> (2)（46%）> (3)（20%）。