含氮杂茂配体的类茂配合物NpCpTiCl_2催化乙烯聚合研究

茂金属催化烯烃聚合时不仅须大量甲基铝氧烷(MAO)作助催化剂,而且其稳定性较差,结构修饰困难,这都一定程度上限制了茂金属催化剂的发展.近几年来,将非环戊二烯类配体与IVB 族金属作用形成的配合物应用于催化烯烃聚合的研究大量出现1],其中非环戊二烯配体有脒化物2,3]、酰胺基4,5]、NFDA3唑啉6]、卟啉7 ]、烷氧基8]、芳氧基9～11]、和β-二酮12,13]、8-羟基喹啉14～16]等.这些非茂配合物均可催化乙烯或丙烯聚合,但活性都较低.我们曾制备了含配位原子为氧或氮的非环戊二烯基配体的半茂配合物,即茂金属中一个环戊二烯基配体被非环戊二烯基配体取代,使金属中心与一个茂和一个非茂配体配位而形成的桥连或非桥连型的配合物17,18].这类配合物不仅稳定性好,而且消耗的助催化剂量较少,活性高,对所得聚合物的结构有一定的控制作用.桥连型半茂配合物以“限制几何构型”催化剂为代表16,19～20 ],非桥连型半茂配合物的报道较少,如CpTi(OiPr)Me2和CpTi(OAr)X2 21 ,22].我们选择氮杂茂类配体为非环戊二烯阴离子配体,氮杂茂环以一价阴离子的形式与金属中心钛配位,与另一个环戊二烯阴离子形成类茂型配合物.这种类茂配合物易于制备, 稳定性好,而且消耗的助催化剂量较小.

CATALYSIS OF THE METALLOCENE ANALOGIC COMPLEX (NpCpTiCl2) CONTAINING THE AZOLE LIGAND (Np) FOR ETHYLENE POLYMERIZATION

Synthesis and elemental analysis of metallocene analogic complexes (NpCpTiCl 2) containing the azole ligand (Np) are described,in which Np is Pr=Pyrolyl (C 4H 4N)(1); Id=Indolyl (C 8H 6N)(2); Ai=7 Azaindolyl (C 7H 5N 2)(3); Iz=Indazolyl (C 7H 5N 2)(4); Bi=Benzimidazolyl (C 7H 5N 2)(5),respectively.It is proved by the experiments that NpCpTiCl 2 is active for ethylene polymerization at 30℃ and 0.1?mPa with MAO activation,and the results show that the activity of 1 and 2 which contain one nitrogen in the azole ring is higher than 4 and 5 which contain two nitrogens,while 3 is inactive.For the NpCpTiCl 2/MAO system,the activity is “up and down” type with increase in the Al/Ti molar ratio,and up to the highest when the Al/Ti molar ratio is about 500.The polyethylene obtained is characteristic of narrow distribution with molecular weight M w around 35×10 4 and molecular weight ratio M w/ M n less than 3.