Ligand induced PH bond formation and a comparison of the reactivity of two isomers of the carbonyl hydride [Pt2(μ-PBut 2)2(H)(CO)(PBut 2H)]CF3SO3

The Pt2 (II) isomeric terminal hydrides [(CO)(H)Pt(μ-PBut 2)2Pt(PBut 2H)]CF3SO3 (1a), and [(CO)Pt(μ-PBut 2)2Pt(PBut 2H)(H)]CF3SO3 (1b), react rapidly with 1 atm of carbon monoxide to give the same mixture of two isomers of the Pt2 (I) dicarbonyl [Pt2(μ-PBut 2)(CO)2(PBut 2H)2]CF3SO3 (3-Pt); the solid state structure of the isomer bearing the carbonyl ligands pseudo-trans to the bridging phosphide was solved by X-ray diffraction. A remarkable difference was instead found between the reactivity of 1a and 1b towards carbon disulfide or isoprene. In both cases 1b reacts slowly to afford [Pt2(μ-PBut 2)(μ,η2,η2-CS2)(PBut 2H)2]CF3SO3 (4-Pt), and [Pt2(μ-PBut 2)(μ,η2,η2-isoprene) (PBut 2H)2]CF3SO3 (6-Pt), respectively. In the same experimental conditions, 1a is totally inert. A common mechanism, proceeding through the preassociation of the incoming ligand followed by the PH bond formation between one of the bridging P atoms and the hydride ligand, has been suggested for these reactions.