The trimethylphosphine adducts of zirconocene and hafnocene silyl hydride complexes have been prepared and the X-ray crystal structure of the zirconocene complex has been determined. In addition, the mechanism of formation of these complexes and a study of the reactivity of the zirconocene complex are presented. The complex Cp2Zr(H)(SiPh3)(PMe3) (2) crystallizes in the monoclinic space group P2(1)/c with a = 9.336 (2) angstrom, b = 28.863 (8) angstrom, c = 11.051 (3) angstrom, beta = 111.11 (2)-degrees, and Z = 4; R(w) = 0.048.