Synthesis of sulfidoosmium carbonyl cluster compounds by the photochemical decomposition of .mu.-(phenylthio)decacarbonylhydridotriosmium [HOs3(CO)10(.mu.-SPh)] and its subsequent reactions with selected small molecules. Synthesis and crystal and molecular structure of (.mu.3-sulfido)(.mu.3-carbonyl)nonacarbonyltriosmium [Os3(CO)9(.mu.3-CO)(.mu.3-S)]