The cluster Os3(CO)11(NCCH3) oxidatively adds across the Sb-H bond in SbPh2H to afford the clusters Os 3(CO)11(H)(μ-SbPh2) and Os 3(CO)11(μ-H)(μ-SbPh2)Os 3(CO)11. Similarly, its reaction with Sb 2Ph4 afforded Os3(CO)11(μ- SbPh2)2Os3(CO)11 as the major product. In both cases, the intermediate from the oxidative addition reaction was trapped as a W(CO)5 adduct. © 2014 American Chemical Society.