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.