Coordination chemistry of group 4 metal compounds with mixed-ligand, silyl-linked bis(amidinate) ligand and cyclopentadienyl

The synthesis and characterization of a class of group 4 metal derivatives based on the silyl-linked bis(amidinate) ligands [SiMe2{NC(Ph)N(2,6-R2Ph)Li}(2)] [L-1 (R = H) and L-2 (R = Me)] are described. The metal salts coordinated with cyclopentadienyl were used in order to increase the steric hindrance and lower the Lewis acidity of metal centers, which could prevent the N-ligands from rearranging. The tetra-dentate ligands L-1 and L-2 reacted with TiCl2(C5H5)(2) to give compounds 1 and 2 in tridentate and bidentate bonding modes, respectively. Treatment of the ligand L-1 with ZrCl3(C5H5) produced the half-sandwich zirconium complex 3. Reactions of the ligands with ZrCl2(C5H5)(2) afforded zirconium compounds 4 and 5, demonstrating the same geometry as 1. Comparing these analogous molecular structures, it suggests that the coordination modes of the N-ligands are variable according to the properties of the metal centers as well as the bulky hindrance of the terminal groups on the seven-membered N-C-N-Si-N-C-N backbone. (C) 2008 Elsevier B. V. All rights reserved.