The bis(acetonitrile-κN)bis[N,N-bis(diphenylphosphanyl)ethanamine-κ2P,P']iron(II) tetrabromidoferrate(II) and μ-oxido-bis[tribromidoferrate(III)] complex salts.

Orange crystals of bis­(acetonitrile-κN)bis­[N,N-bis­(diphenyl­phosphan­yl)ethanamine-κ2P,P′]iron(II) tetra­bromido­fer­rate(II), [Fe(CH3CN)2(C26H25NP2)2][FeBr4], (I), and red crystals of bis­(acetonitrile-κN)bis­[N,N-bis­(diphenyl­phosphan­yl)ethanamine-κ2P,P′]iron(II) μ-oxido-bis­[tribromido­fer­rate(III)], [Fe(CH3CN)2(C26H25NP2)2][Fe2Br6O], (II), were obtained from the same solution after prolonged exposure to atmospheric oxygen, resulting in partial oxidation of the [FeBr4]2− anion to the [Br3FeOFeBr3]2− anion. The asymmetric unit of (I) consists of three independent cations, one on a general position and two on inversion centres, with two anions, required to balance the charge, located on general positions. The asymmetric unit of (II) consists of two independent cations and two anions, all on special positions. The geometric parameters within the coordination environments of the cations do not differ significantly, with the major differences being in the orientation of the phenyl rings on the bidentate phosphane ligand. The ethyl substituent in the cation of (II) and the Br atoms in the anions of (II) are disordered. The P—Fe—P bite angles represent the smallest angles reported to date for octa­hedral FeII complexes containing bidentate phosphine ligands with MeCN in the axial positions, ranging from 70.82 (3) to 70.98 (4)°. The average Fe—Br bond distances of 2.46 (2) and 2.36 (2) A in the [FeBr4]2− and [Br3FeOFeBr3]2− anions, respectively, illustrate the differences in the Fe oxidation states.