New bridging tridentate bis-cyclopentadienyl ligands [C5Me4(CH2)n]2PPh (n = 1, 2) for organometallic synthesis

Preparative procedures were developed for the synthesis of new transmethylated bis-cyclopentadienyl ligands with phosphine-containing bridging fragments. These ligands were isolated as the dilithium salts Li₂[(C₅Me₄CH₂)₂PPh] (1) and Li₂[(C₅Me₄CH₂CH₂)₂PPh] (3). Phosphorus-substituted 3-ansa-zirconocene dichloride [(C₅Me₄CH₂)₂PPh]ZrCl₂ was synthesized starting from 1. The NMR spectroscopic data provide evidence for the absence of the Zr←P coordination interaction in solution. A straightforward approach to 5-ansa-zirconocene dichloride [(C₅Me₄CH₂CH₂)₂PPh]ZrCl₂ starting from lithium salt 3 and ZrCl₄ was shown to be impossible. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1775–1779, September, 2007.