An unusual compound containing μ-O-bridged Re2 6+ cores in very different coordination environments

The reaction of Re2(O2CC6H5)4Cl2 with PMe3 in ethanol in the presence of traces of air or a small amount of H2O2 affords the unusual compound [Cl(PMe3)3Re(μ-O2CC6H5)Re(O)]2(μ-O)2 (1). The crystal structure of this new rhenium ‘dimer of dimers’ type compound has been established by X-ray crystallography. In this centrosymmetric molecule each dirhenium unit is supported by one benzoate ligand and further ligated by Cl, PMe3 and O-ligands; the two dinuclear units are united by two μ-O atoms. Interestingly, the rhenium centers have rarely observed distinctly different coordination environments within the dimers, namely ReClOP3ReO4, which can be formally considered as Re(II)Re(IV) or Re(I)Re(V).