Synthetic and reactivity studies of mono- and dicyclopentadienyl titanium,zirconium and hafnium complexes with the chlorodimethylsilyl-cyclopentadienyl ligand. X-ray molecular structure of Hf{(eta 5-C5H4) SiMe2OSiMe2OSiMe2(eta(5)-C5H4)}Cl-2 and Zr(eta(5)-1,3-(Bu2C5H3)-Bu-t)(eta(5)-C5H4SiMe2-eta-(NBu)-Bu-t)Cl

Reaction of the disilylated cyclopentadiene C5H4(SiClMe2)(SiMe3) with HfCl4 , in heptane, gave the monocyclopentadienyl complex Hf(eta(5)-C5H4SiClMe2)C l-3 (1c). Addition of two equivalents of C5H5(SiClMe2) to a solution of MCl 4, in toluene under reflux and in the presence of two equivalents of NEt3, afforded the dichloro derivatives M(eta(5)-C5H4SiClMe2)(2)Cl-2 [M = Ti (2a) , Hf (2c)]. Compounds 2a and 2c react with a stoichiometric amount of water with selective hydrolysis of the Si-Cl bonds to give the tetramethyldisilo xane-bridged diciclopentadienyl complexes M{(eta(5)-C5H4)SiMe2OSiMe2(eta(5) -C5H4)) Cl-2 [M = Ti (3a), Hf (3c)]. The reaction of the trichloro metal co mpounds M(eta(5)-C5H4SiClMe2)Cl-3 with Tl(1,3-'Bu2C5H3), K(C5Me5) or Tl(C5H 5) afforded the dichloro mixed dicycloyentadienyl MCp'(eta(5)-C5H4SiClMe2)C l-2 derivatives [Cp' = 1,3-'Bu2C5H3, M = Ti (4a), Zr (4b), Hf (4c); Cp' = C 5Me5, M = Zr (5b), Hf (5c); Cp' = C5H5, M = Hf (6c)]. The Si-Cl bond of the mixed dicyclopentadienyl complexes M(eta(5)-1,3-'Bu2C5H3)(eta(5)-C5H4SiClM e2)Cl-2, [M = Ti (4a), Zr (4b), Hf (4c)] reacts selectively with one equiva lent of LiNH'Bu in toluene at 50-60 degrees C to give the amidosilyl(cyclop entadienyl) compounds M(eta(5)-1,3-'Bu2C5H3)(eta(5)-C5H4SiMe2NH'Bu)Cl-2, [M = Ti (7a), Zr (7b), Hf (7c)]. The same reaction with two equivalents of th e lithium amide gives the ansa -cyclopentadienylsilyl-amido compounds M(eta (5)-1,3-'Bu2C5H3)(eta(5)-C5H4SiMe2-eta-N'Bu)Cl [M = Ti (8a), Zr (8b), Hf (8 c)]. The X-ray molecular structure of Hf((eta(5)-C5H4)SiMe2OSiMe2(eta(5)-C5 H4)}Cl-2 (3c) and Zr(eta(5)-1,3-'Bu2C5H3)(eta(5)-C3H4SiMe2-eta-N'Bu)Cl (8b) have been determined by diffraction methods. (C) 2000 Elsevier Science S.A . All rights reserved.