Structural features of Me2Si-Bridged Cp/Phosphido group 4 metal complexes, "CpSiP" constrained-geometry Ziegler-Natta catalyst precursors

Double deprotonation of [(C5Me4H)-SiMe2-PH(cyclohexyl)] (4) was achieved by treatment with n-butyllithium in THF/pentane to afford the dianionic ligand [(C5Me4)-SiMe2-P(cyclohexyl)](2-) as its dilithio salt (5). The reagent 5 was transmetalated by subsequent treatment with [Cl2Ti(NMe2)(2)] (6a) to yield the dimethylsilanediyl-bridged Cp*/phosphido titanium complex [(C5Me4)-SiMe2-PCy]Ti(NMe2)(2) (7a; 67% isolated yield). The analogous reaction of 5 with [Cl2Zr(NEt2)(2)(THF)(2)] (6b) gave [(C5Me4)-SiMe2-PCy]Zr(NEt2)(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.