A Cubane-Substituted Polyoxoanion: Structure and Magnetic Properties of Cs(2)[H(2)PW(9)Ni(4)O(34)(OH)(3)(H(2)O)(6)].5H(2)O.

The novel polyoxometalate [H(2)PW(9)Ni(4)O(34)(OH)(3)(H(2)O)(6)](2)(-) (1) has been synthesized and characterized by IR spectroscopy, polarography, elemental analysis, and magnetic measurements. An X-ray single-crystal analysis was carried out on Cs(2)[H(2)PW(9)Ni(4)O(34)(OH)(3)(H(2)O)(6)].5H(2)O, which crystallizes in the orthorhombic system, space group Pbcn, with a = 24.3131(3) Å, b = 21.5400(1) Å, c = 19.8936(3) Å, V = 10418.4(2) Å(3), Z = 8, and rho(calcd) = 3.767 g/cm(3). Structural analysis based on 14 734 independent reflections leads to a solution, R = 8.04% (I > 2sigma(I)). Anion 1 consists of a Ni(4)O(4) cubane fragment which is inserted into a trivacant lacunary B-alpha-[PW(9)O(34)](9)(-) Keggin unit. Magnetic measurements show that the Ni-Ni exchange interactions are ferromagnetic.