Oxidative Addition of Group 14 Hydrides to an Unsaturated Metal Cluster. Kinetics of Addition of HER₃ (ER₃ = SiEt₃, SiPh₃, GeBu₃, SnBu₃, SnPh₃) to H₂Os₃(CO)₁₀

The kinetics and mechanism of oxidative addition of HER₃ = HSiEt₃, HGeBu₃, HSnBu₃, HSnPh₃ to the unsaturated cluster H₂Os₃(CO)₁₀, initially forming H₃Os₃(CO)₁₀(ER₃), are reported. For HSiEt₃ the addition is readily reversible, with an equilibrium constant of 100 M^-1 at 303 K. In each case the rate law for the forward reaction is first-order in both reagents. Rate constants (M^-1 s^-1) at 303 K are as follows:  HSnBu₃ (23) > HSnPh₃ (1.5) > HGeBu₃ (0.15) > HSiEt₃ (3.8 × 10^-3). Comparisons are made to additions of group 14 element hydrides to 16-electron Ir(I) complexes. The reaction with HSiPh₃, which forms H₃Os₃(CO)₉(SiPh₃) and further addition products, was also examined.