Synthesis, Spectra and Crystal Structure of Tetrakis(Triphenylarsine Oxide)Iron(III)-μ-Oxo-Tribromoiron(III) Tetrabromoferrate(III)-Acetonitrile

Abstract

The oxidation of triphenylarsine with dioxygen in reaction systems containing some iron compound and Br- anions in acetonitrile leads to the formation of a novel unsymmetrical oxo-bridged diiron(III) complex [(OAsPh3)4 Fe(μ-O)FeBr3]+ [FeBr4]- ·CH3CN, where OAsPh3 is triphenylarsine oxide. The title complex is also formed by direct reaction of iron(III) bromide and OAsPh3 with dioxygen in acetonitrile solution. The crystal structure of the complex was solved by X-ray diffraction techniques. The cation contains two unsymmetrical species with an Fe-O-Fe bond angle of 159.2(2)°; one iron atom is pentacoordinated by four OAsPh3 ligands and a γ-oxo ligand which connects the tetracoordinated Fe atom with the FeBr3O chromophore. Structural parameters and IR spectra of similar complexes are compared and discussed.