Decarbonylation reactions of formic acid by Group Vlll halide complexes have been used to prepare new halogenocarbonyl complexes of the form c~s-[M(CO),X,]~-and cis-[M(CO),X,]-( M = 0 s or Ru; X = CI, Br, or I), [OS(CO)X,]~-and [M(CO),X,],(M = 0 s or Ru; X = Cl or Br), [M(CO)XJ2-(M = Ir, Rh, or Ru; X = CI or Br), and [Pt(CO)X,]-(X = CI or Br). A number of triphenylphosphine derivatives of these products were also made, e.g. M(CO),X,(PPh,), (M = 0 s or Ru; X = CI or Br). The vibrational spectra of the halogenocarbonyls were measured and assignments of fundamental modes proposed. The spectra of pentahalogeno-carbonyl and -nitrosy1 species were compared and 13C and 15N substitution used to confirm the assignments.WE recently briefly reported a number of new anionic octahedral halogeno-carbonyl complexes of ruthenium, osmium, and iridium, made by reaction of formic acid with metal halide species.l We now show that a wide range of such products may be prepared by careful control of reaction conditions. The Raman and i.r. spectra of the products in the solid state and in aqueous solution have been measured since the simple structures of the complexes should permit assignment of metalcarbon stretching and bending vibrations. We have already reported spectra of a number of mononitrosyl complexes of the form [M(NO)X6]n-; here we report their Raman spectra and compare the results with the spectra of [M(CO)X,]n-species.
