SYNTHESIS OF NEW MIXED RING ZIRCONOCENES AND EVIDENCE OF RING LOSS

The synthesis of the substituted silyl cyclopentadiene ligand [C5H5-Si (CH3)(2)(p-C6H4Br)] ((CpH)-H-Si) (1) is described. Deprotonation of (i ) gives ((CpLi)-Li-Si) (2) which reacts with 1/2 ZrCl4 to produce the bent, sandwich complex Zr(Cp-Si)(2)Cl-2 (3). Compound (3) can be alkyl ated to give Zr(Cp-Si)(2)(CH3)(2) (4). Reaction of CpZrCl3 .(Et2O)(1/ 2) with (2) in ether produces (3) and Zr(Cp-Si)(C5Me5)Cl-2 (5) as the minor and major products, respectively, whereas reaction in toluene pr oduces only 5. Et2O and THF are found to catalyze the observed ring lo ss during the synthesis of 5. Alkylation of 5 produces Zr(Cp-Si)(C5Me5 )(CH3)(2) (6). (C) 1998 Elsevier Science S.A. All rights reserved.