from first principles PP-I-1

PP-II-71 H NMR Study of Activation of Dimethylated 2-Substituted BisindenylZirconocenes with Triisobutylaluminum and Isobutylalumoxanes inPolymerization of Hexene-1Faingol’d E.E., Babkina O.N., Zharkov I.V., Bravaya N.M.Institute of Problems of Chemical Physics Russian Academy of Sciences,142432, pr. akademika Semenova 1, Chernogolovka, Moscow Region, Russiafevgeny@mail.ruThe most common and effective activator of metallocene and post-metallocene catalysts inhomo- and copolymerization of olefins is polymethylalumoxane (MAO). However the mostsignificant drawback of MAO is the high cost and necessity to use it at high molar excess tothe precatalyst (Al MAO /precatalyst=10 3 -10 4 mol/mol). That’s why the search of new effectiveand cheap activators or the ways of activation is the task of high priority. In our publications[1,2] we have shown that dimethylated 2-substituted bisindenyl zirconocenes are activated bytriisobutylaluminum (TIBA) at low molar ratio Al TIBA / Zr ~ 10 2 mol/mol. The activity andstereospecificity of such systems in propylene polymerization is commensurable with MAOactivated ones. The aim of the work was 1 H NMR study of metallocene activation by TIBAand isobutylalumoxanes, the products of TIBA hydrolysis.Zirconocenes rac-Et (2-MeInd) 2 ZrMe 2 (1) and rac-Ме 2 Si(2-Me,4-PhInd) 2 ZrCl 2 (2) werechosen for 1 H NMR studies. Analysis of NMR spectra of catalytic systems 1 (2)/TIBA and1 (2)/TIBA/hexene-1 showed that, in fact, an activator of dimethylated 2-substitutedbisindenyl zirconocene were isobutylalumoxane impurities contained in a toluene solution ofcommercial TIBA. Experiments with TIBA free from impurities showed the formation ofcomplexes 1 (2)·TIBA which were inactive in 1-hexene polymerization. Syntheses ofdifferent isobutylalumoxanes by hydrolysis of TIBA are presented. It was shown thatisobutylalumoxanes (IBAO) are very effective activators of 1 (2) zirconocenes in 1-hexenepolymerization at low molar ratios of Al/Zr (10 1 -10 2 ).Acknowledgement:The work was supported by the Russian Foundation for Basic Research (project№ 10-03-00926-a) and Ministry of Education and Science of RF. (project № 02.740.11.0646).References:[1] A. N. Panin, Z. M. Dzhabieva, P. M. Nedorezova, V. I. Tsvetkova, S. L. Saratovskikh,O. N. Babkina, N. M. Bravaya, J.Polym.Sci. Part A: Polym.Chem, 39 (2001) 1915.[2] N.M. Bravaya, A.N. Panin, E.E. Faingol’d, O.N. Babkina, A. Razavi, J. Polym. Sci. A: Polym.Chem. 43 (2010) 2934.138