Anionic halogenocarbonyls of rhodium, iridium, and platinum

The decarbonylation of formic acid by platinum metal halogeno-complexes in the presence of the appropriate halogen acid provides a simple method for the preparation of salts containing the anions [MIII(CO)l5]2–, [RuIII(CO)Br5]2–, [OsIII(CO)Y5]2–, [IrIII(CO)Br4(MeOH)]–, [IrIII(CO)Br4]22–, [RhIII(CO)X4(MeOH)]–, [RhIII(CO)X4]22–, cis-[IrIII(CO)2X4]–, [PtII(CO)X3]–, cis-[IrII(CO)2Y3]22–, [Ir4II, I(CO)8X8]2–, cis-[IrI(CO)2Br2]– and cis-[RhI(CO)2Y2]–(M = Rh or Ir; X = Cl, Br, or I; Y = Cl or Br). Raman and i.r. spectra of these complexes have been studied and assignments of fundamental modes suggested. The structures of the complexes are discussed.