Structural Features of Me<INF>2</INF>Si-Bridged Cp/Phosphido Group 4 Metal Complexes, “CpSiP” Constrained-Geometry Ziegler−Natta Catalyst Precursors

Double deprotonation of [(C<INF>5</INF>Me<INF>4</INF>H)−SiMe<INF>2</INF>−PH(cyclohexyl)] (<BO>4</BO>) was achieved by treatment with n-butyllithium in THF/pentane to afford the dianionic ligand [(C<INF>5</INF>Me<INF>4</INF>)-SiMe<INF>2</INF>−P(cyclohexyl)]^2- as its dilithio salt (<BO>5</BO>). The reagent <BO>5</BO> was transmetalated by subsequent treatment with [Cl<INF>2</INF>Ti(NMe<INF>2</INF>)<INF>2</INF>] (<BO>6a</BO>) to yield the dimethylsilanediyl-bridged Cp*/phosphido titanium complex [(C<INF>5</INF>Me<INF>4</INF>)−SiMe<INF>2</INF>−PCy]Ti(NMe<INF>2</INF>)<INF>2</INF> (<BO>7a</BO>; 67% isolated yield). The analogous reaction of <BO>5</BO> with [Cl<INF>2</INF>Zr(NEt<INF>2</INF>)<INF>2</INF>(THF)<INF>2</INF>] (<BO>6b</BO>) gave [(C<INF>5</INF>Me<INF>4</INF>)−SiMe<INF>2</INF>−PCy]Zr(NEt<INF>2</INF>)<INF>2</INF> (<BO>7b</BO>; isolated in 59% yield). Single crystals of the complexes <BO>7a</BO>,<BO>b</BO> 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 <BO>7a</BO>,<BO>b</BO> both give active homogeneous Ziegler−Natta catalysts for ethene/1-octene copolymerization upon activation with excess methylalumoxane.