Diverse coordination behaviors of the silyl-linked bis(amidinate) ligand [SiMe2{NC(Ph)N(Ph)}2]2- to zirconium center

The reactions between the silyl-linked bis(amidinate) ligand [SiMe2{NC(Ph)N(Ph)Li(thf)(2)}(2)] and ZrCl4 in different stoichiometric chemistry, 2:1. 1:1, and 1:2, were explored. The resulting zirconium compounds, 1, 2, and 3, showed different molecular structural features which were confirmed by X-ray crystallographic analysis. The metal center in I was located in a highly saturated coordination environment with four amidinate moieties. Compound 2 exhibited an unprecedented linked tris(amidinate) N-C-N-Si-N-C-N-Si-N-C-N skeleton formed after the intermolecular rearrangement. In compound 3, a novel silyl-linked imino-amidinate ligand via the intramolecular rearrangement was involved. The mechanism for the formation Of Compounds 2 and 3 was proposed. Compound 2 was found to be a highly active catalyst for ethylene polymerization in the presence of methylalumoxane (MAO). (C) 2009 Elsevier Ltd. All rights reserved.