Ligand Induced P-H Bond Formation vs Ligand Substitution, and a Comparison of the Reacivity of Two Isomers of [Pt2(m-PBut2)2(PBut2H)(CO)(H)]CF3SO3

The Pt-2((II)) isomeric terminal hydrides [(CO)(H)Pt(mu-PBu21)(2)Pt((PBu2H)-H-1)]CF ISO, (1a), and [(CO)Ptmu-Bu-2(1))(2)Pt((PBu2H)-H-1)(H)]CF3SO3 (1b), react rapidly with 1 atm of carbon monoxide to give the same mixture of two isomers of the P-2((I)) dicarbonyl [Pt-2(mu-PBu21)(CO)(2)((PBu2H)-H-1)(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 la and 1b towards carbon disulfide or isoprene. In both cases 1b reacts slowly to afford [Pt-2(mu-PBu21)(mu,eta(2),eta(2)-CS2)((PBu2H)-H-1)(2)]CF3SO3 (4-Pt), and [Pt-2(mu-PBu21)(mu,eta(2),eta(2)-isoprene) ((PBu2H)-H-1)(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.