CHARGE-TRANSFER INTERACTIONS BETWEEN SULFUR-DIOXIDE AND GROUP-8 HALF-SANDWICH COMPLEXES

Mulliken-type charge-transfer complexes have been formed between basic half-sandwich compounds and SO2 when [M(eta(5)-C(5)R(5))(CO)(2)] (M = Rh or Ir; R(5) = Me(5), H-5 or H4CF3), [Ir(eta(5)-C5H5)(CO)(C2H4)], and [M(eta(5)-C5H5)(C2H4)(2)] (M = Co, Rh or Ir) are isolated in SO2-doped argon matrices at 20 K; the nu(CO) bands of the complexes are shifted to high frequency of those of the precursor molecules and prominent charge-transfer bands are observed; the same species have been detected when the compounds [M(eta(5)-C(5)Me(5))(CO)(2)] (M = Rh or Ir) are embedded in polyethylene discs and treated with SO2 at 213-298 K; the enthalpy of complexation of [Ir(eta(5)-C(5)Me(5))(CO)(2)] with SO2 is -13 +/- 3 kJ mol(-1).