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 revers ible, with an equilibrium constant of 100 M-1 at 303 K. In each case the ra te law for the forward reaction is first-order in both reagents. Rate const ants (M-1 s(-1)) at, 303 K are as follows: HSnBu3 (23) > HSnPh3 (1.5) > HGe Bu3 (0.15) > WSiEt3 (3.8 x 10(-3)). Comparisons are made to additions of gr oup 14 element hydrides to 16-electron Ir(I) complexes. The reaction with H SiPh3, which forms H3Os3(CO)(9)(SiPh3) and further addition products, was a lso examined.