Reactions of osmium tetraoxide with triphenylphosphine. Reformulation of oxotrichlorobis(triphenylphosphine)osmium(V)

Article abstract of DOI:10.1021/ic50187a009

The osmium(V) complex OsOCl₃(PPh₃)₂, which was purported to be formed upon reacting osmium tetraoxide with triphenylphosphine and hydrochloric acid in refluxing ethanol, is shown to be a mixture of OsO₂Cl₂(PPh₃)₂ and trans-OsCl₄(PPh₃)₂. This conclusion is supported by infrared and X-ray photoelectron spectroscopic (XPS) measurements and the isolation of analytically pure samples of the osmium(VI) and osmium(IV) complexes. The dicarbonyl complex Os(CO)₂Cl₂(PPh₃)₂ has also been isolated from the OsO₄-PPh₃-HCl reaction mixture in ethanol when long reflux periods (6-8 h) are used. The reaction of OsO₂Cl₂(PPh₃)₂ with refluxing pyridine produces the osmium(II) complex OsCl₂(py)₃(PPh₃), while trans-OsCl₄(PPh₃)₂ is reduced to the osmium(III) complexes OsCl₃(py)₂(PPh₃) and OsCl₃(PPh₃)₂(CH₃CN) by pyridine and acetonitrile, respectively. These mixed-ligand complexes exhibit a rich redox chemistry as demonstrated by cyclic voltammetry.