Synthesis and Reactivities of Polyhydrido Osmium Arylsilyl Complexes Prepared from OsH₃Cl(PPh₃)₃

Reactions of silanes with transition-metal complexes are of interest because their relevance to Si–H bond activation, the structural properties of polyhydrides, and catalytic hydrosilylation reactions. This work presents the results derived from reactions of arylsilanes Ph₂SiH₂ and PhSiH₃ with OsH₃Cl­(PPh₃)₃ (1). Reaction of 1 with 1 equiv or excess Ph₂SiH₂ affords OsH₃(SiClPh₂)­(PPh₃)₃ (2) or OsH₄(SiClPh₂)­(SiHPh₂)­(PPh₃)₂ (3), respectively. These silyl complexes are formed via the oxidative addition of Si–H bonds and H/Cl exchange via silylene intermediates. Similarly, reaction of 1 with excess PhSiH₃ produced the analogous bis­(silyl) complex OsH₄(SiClHPh)­(SiH₂Ph)­(PPh₃)₂ (4). The bis­(silyl) complexes are dodecahedral tetrahydride complexes containing weak Si···H interactions. The complex 3 reacts with PPh₃ and CH₃CN to selectively eliminate Ph₂SiH₂. Computational studies show that the preference for reductive eliminations from 3 follows the order Ph₂SiH₂ > H₂ > Ph₂SiHCl > Ph₂HSi-SiClPh₂.