Rhodium(I) and rhodium(III) carbonyl complexes containing tertiary phosphines or tertiary arsines and halogen formed by the decarbonylation of alcohols and by the direct use of carbon monoxide
Convenient syntheses of many new rhodium(I) and rhodium(III) complexes of types trans-[RhX(CO)L2](X = Cl, Br, I, or SCN; L = PR3 or AsR3) and [RhX3(CO)L2](X = Cl or Br; L = PR3) are described which involve treating rhodium complexes with carbon monoxide. Several of the complexes trans-[RhX(CO)(PR3)2] were also conveniently prepared by treating rhodium(III) complexes of type [RhX3(PR3)3] with a primary alcohol in the presence of a base (e.g., potassium hydroxide). The carbon monoxide ligand is derived from the alcohol, and the residual fragments from the alcohols, e.g., methane from ethanol, have been identified. Reactions of the rhodium(I) compounds described include metathesis of the halogen, addition of chlorine or acetyl halides, the action of halogen acids, and displacement of ligands by the chelating phosphine Ph2P·CH2·CH2·PPh2 to give [Rh(Ph2P·CH2·CH2·PPh2)2]Cl. The rhodium(III) complex [RhCl3(CO)(PEt2Ph)2] was reduced to the rhodium(I) complex [RhCl(CO)(PEt2Ph)2] by ethanol and potassium hydroxide. Infrared [ν(CO)] and dipole moment data are given.