Charge-transfer interactions between sulfur dioxide and group 8 half-sandwich complexes

Abstract

Mulliken-type charge-transfer complexes have been formed between basic half-sandwich compounds and SO₂ when [M(η⁵-C₅R₅)(CO)₂](M = Rh or Ir; R₅= Me₅, H₅ or H₄CF₃), [Ir(η⁵-C₅H₅)(CO)(C₂H₄)], and [M(η⁵-C₅H₅)(C₂H₄)₂](M = Co, Rh or Ir) are isolated in SO₂-doped argon matrices at 20 K; the ν(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 (η⁵-C₅Me₅)(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(η⁵-C₅Me₅)(CO)₂] with SO₂ is –13 ± 3 kJ mol^–1.