The reaction of hydridocarbonyltris(triphenylphosphine)rhodium with carbon monoxide, and of the reaction products, hydridodicarbonylbis(triphenylphosphine)rhodium and dimeric species, with hydrogen

A detailed study has been made, using infrared and nuclear magnetic resonance techniques, of the interaction of carbon monoxide and hydridocarbonyltris(triphenylphosphine)rhodium(I), RhH(CO)(PPh3)3. The latter, which dissociates in solution to the square complex trans-RhH(CO)PPh3)2, initially forms the dicarbonyl complex RhH(CO)2(PPh3)2; in the presence of CO, this species loses hydrogen to give a yellow dimeric complex (Ph3P)2(CO)Rh(CO)2Rh(CO)(PPh3)2. These reactions are reversed by hydrogen to re-form RhH(CO)(PPh3)2. By sweeping with an inert gas, the yellow dimer loses carbon monoxide to form a red, solvated dimer, (Ph3P)2(S)Rh(CO)2Rh(S)(PPh3)2, which reacts with carbon monoxide to re-form the yellow dimer.