The satellite-shaped Co-15 polyoxotungstate, [Co6(H2O)30}Co9Cl2(OH)3(H2O)9(ß-SiW8O31)3}]5-

The 15-cobalt-substituted polyoxotungstate [CO6(H2O)(30){Co9Cl2(OH)3(H2O)(9)(beta-SiW8O31)(3)}](5-) (1) has been characterized by single-crystal XRD, elemental analysis, IR, electrochemistry, magnetic measurements, and EPR. Single-crystal X-ray analysis was carried out on Na-5[CO6(H2O)(30){Co9Cl2(OH)(3)(H2O)(9)(beta-SiW8O31)(3)}]center dot 37H(2)O, which crystallizes in the hexagonal system, space group P6(3)/m, with a = 19.8754(17) angstrom, b = 19.8754(17) angstrom, c = 22.344(4) angstrom, alpha = 90 degrees, beta = 90 degrees, gamma = 120 degrees, and Z = 2. The trimeric polyanion 1 has a core of nine Coll ions encapsulated by three unprecedented (beta-SiW8O31) fragments and two Cl- ligands. This central assembly {Co9Cl2(OH)(3)(H2O)(9)(beta-SiW8O31)(3)}(17-) is surrounded by six antenna-like Co-parallel to(H2O)(5) groups resulting in the satellite-like structure 1. Synthesis of 1 is accomplished in a simple one-pot procedure by interaction of Coll ions with [gamma-SiW10O36](8-) in aqueous, acidic NaCl medium (pH 5.4). Polyanion 1 was studied by cyclic voltammetry as a function of pH. The current intensity of its Co-parallel to centers was compared with that of free Coll in solution. Our results suggest that 1 keeps its integrity in solution. Magnetic susceptibility results show the presence of both antiferro- and ferromagnetic coupling within the (Coll)9 core. A fully anisotropic Ising model has been employed to describe the exchange-coupling and yields g = 2.42 +/- 0.01, J(1) = 17.0 +/- 1.5 cm(-1), and J(2) = -13 +/- 1 cm(-1). Variable frequency EPR studies reveal an anisotropic Kramer's doublet.