Hydrothermal synthesis and crystal structure of a heteropolyoxotungstate formed by sandwich-type heteropolyanion [Gd(PW11O39)(2)](11-) and reduced [Cu(en)(2)](+) cations

A heteropolyoxotungstate, [Cu(en)(2)](2)H-8[Gd(PW11O39)(2)] (H(2)en)(0.5) center dot 3H(2)O (1), has been hydrothermally synthesized and characterized by IR, XPS, TGA and single-crystal X-ray diffraction. Compound 1 crystallizes in the triclinic system, space group P (1) over bar, with a = 12.651(2) angstrom(3), b = 20.559(3) angstrom(3), c = 21.729(3) angstrom(3), alpha = 71.379(2), beta = 82.829(2), gamma = 75.532(2)degrees, V = 5179.5(14) angstrom(3), Z = 2, R-1 = 0.0702 and R-2 = 0.1479. The heteropolyanion is composed of two monovacant [alpha-PW11O39](7-) Keggin moieties linked via a Gd atom leading to a sandwich-type structure. The Gd center is in a distorted square antiprismatic coordination environment with eight oxygen atoms, four from each of the two [alpha-PW11O39](7-) moieties.