Structure and spectral characteristics of (NH4)2[Re2(HPO4)4 • 2H2O]

The compound (NH4)(2)[Re-2(HPO4)(4) center dot 2H(2)O] has been synthesized and characterized by electronic and vibrational spectroscopy. The molecular structure has been determined by X-ray diffraction (MoK (alpha) radiation, lambda = 0.71073 angstrom). The (NH4)(2)[Re-2(HPO4)(4) center dot 2H(2)O] coordination units form centrosymmetrical binuclear ordering with each metal atom being coordinated in a distorted octahedron incorporating one rhenium atom, one oxygen atom of the water molecule, and four phosphate oxygen atoms in the equatorial plane. The rhenium-rhenium bond length (2.2207 angstrom) corresponds to a quadruple bond between the atoms. The [Re-2(HPO4)(4) center dot 2H(2)O](2-) complex anions in the crystal are associated through strong hydrogen bonds formed by the phosphate O-H center dot center dot center dot O groups. The stability of dirhenium(III) tetra-mu-phosphates in aqueous solutions is considered.