Patent ID: 7652160

Claim:
A compound having the formula: wherein M 2 is Zr or Hf; (R 5A ) and (R 5B ) are independently a hydrocarbyl group or a trihydrocarbylsilyl group, any of which having up to 20 carbon atoms, or hydrogen; n is an integer from 0 to 10, inclusive; and (X 3A ) and (X 4A ) are independently: 1) F, Cl, Br, or I; 2) a hydrocarbyl group having up to 20 carbon atoms, H, or BH 4 ; 3) a hydrocarbyloxide group, a hydrocarbylamino group, or a trihydrocarbylsilyl group, any of which having up to 20 carbon atoms; or 4) OBR A 2 or SO 3 R A , wherein R A is an alkyl group or an aryl group, any of which having up to 12 carbon atoms.