Synthesis, Structure and Reactivity of Bis(phosphido)-Bridged Dinuclear Carbonyls of Platinum(I)

The platinum(I) dinuclear carbonyl [Pt-2([mu-PtBu2)(2)(PtBu2H)-(CO)] (4) reacts with carbon monoxide (80atm) to give the dicarbonyl complex [Pt(mu-PtBu2)(CO)](2) (9), which is thermally and air stable if protected from moisture. Wet solvents convert 9 into the known trinuclear hydride Pt-3(mu-PtBu2)(3)(CO)(2)- (H) (10), which is also formed by treating 9 with molecular hydrogen (180 atm). The reaction of 4 or 9 with phosphanes [PR3 = PMe3, PPh3, PCy3, PCy2H] results in the formation of the corresponding derivatives [Pt-2(mu-PtBu2)(2)(PtBu2H)(PR3)] [11, R = Me; 12, R = Ph; 13, R = Cy; 14, R-3 = Cy2H], [Pt-2(mu-PtBu2)(2)(CO)(PR3)] (15, R Me; 16, R = Ph; 17, R = Cy] or [Pt(mu-PtBu2)(PR3)](2) [18, R Me; 19, R = Ph; 20, R = Cy] in good yields. Complex 19 is protonated at platinum by CF3SO3H yielding the hydride [Pt-2(mu-PtBu2)(2)(H)(PPh3)(2)]-CF3SO3 (21). The protonation of asymmetrically substituted 12 forms rapidly the kinetic hydride [(tBu(2)HP)Pt(mu-PtBu2)(2)-Pt(H)(PPh3)]CF3SC)(3) (22a), which then isomerises slowly to the more stable isomer [(Ph3P)Pt(mu-PtBu2)(2)Pt(H)(PtBu2H)]-CF3SO3 (22b). Dicarbonyl 9 is instead protonated at the phosphorus atom of a bridging phosphide; the unstable product of this reaction can be intercepted by adding CO to give the monophosphido-bridged [Pt-2(mu-PtBu2)(PtBu2H)(CO)(3)]CF3SO3 (24) as a mixture of two isomers. The X-ray crystal and molecular structures of 9, of a 2:1 mixture of 9 and 10, and of complexes 18, 19 and 21 are also reported.