Catalytic hydrogenation of olefins stands as one of the most important and fundamental transformations in syn- thetic organic chemistry. The strive for selectivity in this process has led to the development of numerous hetero- geneous, and homogeneous ~atalysts.~ Although kinetic rate studies indicate that many of these should provide high selectivity in reduction of monosubstituted olefins in the presence of more highly hindered ... (1) Alfred P. Sloan Fellow, 1987-1991; American ...