Synthesis and characterisation of alkylaluminium benzimidazolates and their use in the ring-opening polymerisation of ε-caprolactone
作者:Miao Shen、Wei Huang、Wenjuan Zhang、Xiang Hao、Wen-Hua Sun、Carl Redshaw
DOI:10.1039/c0dt00514b
日期:——
The stoichiometric reactions of 2-(benzimidazol-2-yl)-6-methylpyridine (L1) or 8-(benzimidazol-2-yl)quinaldine (L2) with trialkylaluminium reagents R3Al (R = Me, Et and iBu) afforded the corresponding dialkylaluminium benzimidazolate complexes R2AlL (L1, R = Me (1), Et (2), iBu (3); L2 R = Me (4), Et (5), iBu (6)). Treatment of L1 with one or two equivalents of Et2AlCl led to the adducts EtAl(L1)2·AlEtCl2 (7) or Et2AlL1·AlEtCl2 (8), respectively. Complex 7 was also available via treatment of 8 with one equivalent of L1. Reaction of L1 with two equivalents of AlR3 (R = Me or Et) afforded R2AlL1·AlR3 (R = Me, 9; R = Et, 10), which were also formed when 1 or 2 were reacted with AlR3. Reaction of L2 with two equivalents of AlR3 (R = Me or Et) gave the complexes R2AlL2·AlR3 (R = Me, 11; R = Et, 12), which were also formed in the stoichiometric reaction of 4 or 5 with AlR3 (R = Me or Et). Screening of these complexes in the presence of BnOH, for the ring-open polymerisation of ε-caprolactone, revealed appreciable activities. Only the aluminium compounds ligated by 2-(benzimidazol-2-yl)-6-methylpyridine maintained high activity in the absence of BnOH. In all cases, polymers with bi- or multi-modal characteristics were produced.
2-(苯并咪唑-2-基)-6-甲基吡啶(L1)或8-(苯并咪唑-2-基)喹啉(L2)与三烷基铝试剂R3Al(R = 甲基、乙基和异丁基)的化学计量反应生成了相应的双烷基铝苯并咪唑盐复合物R2AlL(L1,R = 甲基(1),乙基(2),异丁基(3);L2 R = 甲基(4),乙基(5),异丁基(6))。用一个或两个当量的乙基二氯铝处理L1,分别得到加成物EtAl(L1)2·AlEtCl2(7)或Et2AlL1·AlEtCl2(8)。复合物7也可以通过用一个当量的L1处理8获得。L1与两个当量的AlR3(R = 甲基或乙基)反应生成了R2AlL1·AlR3(R = 甲基,9;R = 乙基,10),在将1或2与AlR3反应时也会形成这些复合物。L2与两个当量的AlR3(R = 甲基或乙基)反应生成复合物R2AlL2·AlR3(R = 甲基,11;R = 乙基,12),在将4或5与AlR3的化学计量反应中也会形成这些复合物。在BnOH存在下对这些复合物进行筛选,以研究ε-己内酯的开环聚合,显示出显著的活性。只有由2-(苯并咪唑-2-基)-6-甲基吡啶配位的铝化合物在没有BnOH的情况下保持了高活性。在所有情况下,产生的聚合物具有双峰或多峰特征。