Carbonylation of Hydrido–Phosphanido-Bridged Dinuclear Platinum Complexes

The carbonylation of the solvento species [(PHCy2)(L)Pt(μ- PCy2)(μ-H)Pt(PHCy2){κP-P(OH)Cy2}][BF4]2(Pt–Pt) ([1-L]2+, L = CH2Cl2, thf, CH3CN) led to the formation of a singly bridged dicarbonyl PtI compound syn-[(PHCy2)(CO)Pt(μ- PCy2)Pt{κP-P(OH)Cy2}(CO)]+(Pt–Pt) (2+). The reaction proceeded in two steps: 1) Substitution of L by CO to give the intermediate syn-[(PHCy2)(CO)Pt(μ-PCy2)(μ-H)Pt(PHCy2)- {κP-P(OH)Cy2}]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(μ-PCy2){κ2P,O-μ-P(O)Cy2}- Pt(PHCy2)](Pt–Pt) (5). In this case the first step consisted of the carbonylation of 5 to give [(PHCy2)2Pt(μ-PCy2)Pt{κPP( O)Cy2}(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(μ-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.