Structural Features of Me₂Si-Bridged Cp/Phosphido Group 4 Metal Complexes, “CpSiP” Constrained-Geometry Ziegler−Natta Catalyst Precursors

Abstract

Double deprotonation of [(C 5 Me 4 H)−SiMe 2 −PH(cyclohexyl)] ( 4 ) was achieved by treatment with n -butyllithium in THF/pentane to afford the dianionic ligand [(C 5 Me 4 )-SiMe 2 −P(cyclohexyl)] 2 - as its dilithio salt ( 5 ). The reagent 5 was transmetalated by subsequent treatment with [Cl 2 Ti(NMe 2 ) 2 ] ( 6a ) to yield the dimethylsilanediyl-bridged Cp*/phosphido titanium complex [(C 5 Me 4 )−SiMe 2 −PCy]Ti(NMe 2 ) 2 ( 7a; 67% isolated yield). The analogous reaction of 5 with [Cl 2 Zr(NEt 2 ) 2 (THF) 2 ] ( 6b ) gave [(C 5 Me 4 )−SiMe 2 −PCy]Zr(NEt 2 ) 2 ( 7b; isolated in 59% yield). Single crystals of the complexes 7a, b were obtained from pentane. The X-ray crystal structure analyses revealed distorted “constrained geometry” group 4 metal complex structures due to the presence of a chiral, nonplanar coordination geometry at the phosphorus atom. Complexes 7a, b both give active homogeneous Ziegler−Natta catalysts for ethene/1-octene copolymerization upon activation with excess methylalumoxane.