Activation of Hydrogen and Related Small Molecules by the Unsaturated Cluster Complex PtOs₃(CO)₇(PBu^t₃)(μ-PBu^t₂)(μ₄-CHCMeCH)

Reactions of the unsaturated mixed metal cluster complex PtOs₃(CO)₇(PBu^t₃)(μ-PBu^t₂)(μ₄-CHCMeCH), 1, with hydrogen, HGePh₃, and PhC₂H have been investigated. Compound 1 reacts reversibly with hydrogen at room temperature to yield the dihydrido complex PtOs₃(CO)₇(PBu^t₃)(μ-PBu^t₂)(μ₄-CHCMeCH)(μ-H)(H), 2. A computational analysis shows that the hydrogen addition occurs by oxidative addition at the electronically unsaturated platinum atom and passes through two unstable intermediates before giving the final product 2. Compound 1 reacts with HGePh₃ at the Ge−H bond to form the complex PtOs₃(CO)₇(PBu^t₃)(μ-PBu^t₂)(μ₄-CHCMeCH)(GePh₃)(μ-H), 3, but in this reaction the HGePh₃ addition occurred at one of the osmium atoms and a CO ligand was shifted to the platinum atom. Compound 1 reacts with PhC₂H by loss of the platinum atom and the PBu^t₃ ligand to give the compound Os₃(CO)₇(μ-PBu^t₂)[μ₃-η⁵-CHCMeC(H)CCPhH], 4. In the process, the PhC₂H molecule became bonded to the CHCMeCH ligand in 1 and its hydrogen atom was shifted to the phenyl-substituted carbon atom to form a triply bridging CHCMeC(H)CCPhH ligand. All of the products were characterized by single-crystal X-ray diffraction analyses.