Crystal structure of sodium tris(tetramethylammonium) pentamolybdodisulfate(VI) tetrahydrate, Na[NMe4]3S2Mo5O23·4H2O

Abstract

The structure of Na[NMe₄]₃S₂Mo₅O₂₃·4H₂O has been determined by the single-crystal X-ray method: monoclinic, space group P2/c, a= 29.25(2), b= 12.85(1), c= 18.24(1)Å, and β= 123.89(2)° and Z= 6. The structure was refined by full-matrix least squares to R′= 0.0678 for 5532 reflections. The existence of the Strandberg-type heteropolyion [S₂Mo₅O₂₃]^4–1 in the crystals has been confirmed. The geometry of 1 was compared systematically with various analogues containing S^IVO₃^2–, PO₄^3–, MePO₃^2– or NH₃C₂H₄PO₃^– as the central polyhedron. The UV spectrum of the salts Na[NMe₄]₃S₂Mo₅O₂₃·4H₂O and [NMe₄]₄S₂Mo₅O₂₃ in neat MeCN, hence the kernel heteropolyion 1 showed absorption maxima at λ= 213 and 243 nm (ε= 3.2 × 10⁴ and 3.3 × 10⁴ dm³ mol^–1 cm^–1). Spectroscopic measurements also indicate that 1 and [Mo₆O₁₉]^2– form simultaneously in aqueous–MeCN media containing Mo^VI and H₂SO₄.