An unusual dirhenium complex containing the bridging 6-(diphenylphosphino)-2-pyridonate ligand

Abstract

The diamagnetic dirhenium(II) complex Re₂Cl₂(μ-pyphos)₂(pyphosH) (2) is a product of the reactions between (n-Bu₄N)₂Re₂Cl₈, Re₂(μ-O₂CMe)₄Cl₂ or cis-Re₂ (μ-O₂CMe)₂Cl₄(H₂O)₂ and 6-diphenylphosphino-2-pyridone (pyphosH) in refluxing acetonitrile. This formulation is based upon a single crystal X-ray structure determination and measurements of the magnetic susceptibility, EPR spectrum, electronic absorption spectrum and cyclic voltammetric properties of 2. Unlike the known dimolybdenum(II) complex Mo₂(μ-pyphos)₄, which contains four N,O-bound pyphos ligands, all three bridging ligands in 2 are N,P-bound. The two anionic pyphos ligands are also involved in weaker ‘axial’ coordination of their O atoms to the dirhenium core. The dirhenium units are linked into dimers-of-dimers through strong intermolecular hydrogen bonds.