Carbonylation of Hydrido-Phosphanido-Bridged Dinuclear Platinum Complexes

The carbonylation of the solvento species [(PHCy2)(L)Pt(-PCy2)(-H)Pt(PHCy2){P-P(OH)Cy-2}][BF4](2)(Pt-Pt) ([1-L](2+), L = CH2Cl2, thf, CH3CN) led to the formation of a singly bridged dicarbonyl Pt-I compound syn-[(PHCy2)(CO)Pt(-PCy2)Pt{P-P(OH)Cy-2}(CO)](+)(Pt-Pt) (2(+)). The reaction proceeded in two steps: 1) Substitution of L by CO to give the intermediate syn-[(PHCy2)(CO)Pt(-PCy2)(-H)Pt(PHCy2){P-P(OH)Cy-2}](2+)(Pt-Pt) ([1-CO](2+)) and 2) uptake of a second molecule of CO and elimination of [PH2Cy2](+) (as the BF4- salt) to give 2(+). The dicarbonyl complex [2][BF4] was also synthesized starting from the dicyclohexylphosphanido-bridged complex [(PHCy2)Pt(-PCy2){P-2,O--P(O)Cy-2}Pt(PHCy2)](Pt-Pt) (5). In this case the first step consisted of the carbonylation of 5 to give [(PHCy2)(2)Pt(-PCy2)Pt{P-P(O)Cy-2}(CO)](Pt-Pt) (6), which was transformed into 2(+) by protonation with HBF4 under an atmosphere of CO. Prolonged reaction times for the carbonylation of [1-L](2+) in halogenated solvents resulted in the formation of the symmetrical dicarbonyl compound syn-[(CO)(PHCy2)Pt(-PCy2)Pt(PHCy2)(CO)](+)(Pt-Pt) (3(+)) along with Cy2P(H)OBF3. Complexes 6 and [1-L][BF4](2) were also formed by the carbonylation of 5 and [1-OMe2][BF4](2) in the solid state.