Platinum Promoted Insertion of an Alkyne into a Metal−Hydrogen Bond

HOs(CO)4SnPh3, 1 reacts with PhC2H in the presence to Pt(PBut3)2 to yield the alkyne insertion product PtOs(CO)4(SnPh3)(PBut3)[μ-HC2(H)Ph], 2 containing a Pt(PBut3)(CO) group coordinated to the osmium atom and the alkenyl ligand. In the absence of PhC2H, 1 reacts with Pt(PBut3)2 to form a Pt(PBut3) adduct, PtOs(CO)4(SnPh3)(PBut3)(μ-H), 3 at the Os−H bond. This adduct is readily transformed to 2 upon reaction with PhC2H. In the absence of the Pt(PBut3) promoter, PhC2H does not react with 1.