Synthesis of new mixed ring zirconocenes and evidence of ring loss

Article abstract of DOI:10.1016/S0022-328X(97)00786-9

The synthesis of the substituted silyl cyclopentadiene ligand [C₅H₅-Si(CH₃)₂(p-C₆H ₄Br)] (Cp^SiH) (1) is described. Deprotonation of (1) gives (Cp^SiLi) (2) which reacts with 1/2 ZrCl₄ to produce the bent, sandwich complex Zr(Cp^Si)₂Cl₂ (3). Compound (3) can be alkylated to give Zr(Cp^Si)₂(CH₃)₂ (4). Reaction of Cp*ZrCl₃·(Et₂O)_1/2 with (2) in ether produces (3) and Zr(Cp^Si)(C₅Me₅)Cl₂ (5) as the minor and major products, respectively, whereas reaction in toluene produces only 5. Et₂O and THF are found to catalyze the observed ring loss during the synthesis of 5. Alkylation of 5 produces Zr(Cp^Si)(C₅Me₅)(CH₃)₂ (6).