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Reactions of the hexanuclear clusters of niobium and tantalum with mercury(II) halides

Mercury(II) halides react with [(M_6Br_(12))Br_2(H_2O)_4]×4H_2O to yield the compounds of the composition [M_6Br_(12)(H_2O)_6][HgBr_2X_2]×12H_2O (M = Nb, Ta; X = Cl, Br; I). The substances crystallize in the cubic crystallographic system and contain complex cations [M_6Br_(12)(H_2O)_6]^(2+) and tetrahedrally coordinated mercury(II) atom in [HgX_4]^(2-) anions. The magnetic susceptibility measurement of [Nb_6Br_(12)(H_2O)_6][HgBr_4]×12H_2O in the temperature range 4.2 to 300 K indicates diamagnetic behaviour; the electrical conductivity measurement on the single crystal gives a value of sigma_(295 K) = 0.01 Omega^(-1) cm^(-1) (E_a = 0.20 eV), characteristic for semiconducting materials. To the same crystallographic system belong the substances with [Ta_6Cl_(12)(H_2O)_6]^(3+) cation. These compounds are paramagnetic with large spin temperature dependent magnetic susceptibility. Data on electronic, magnetic and electrical properties for [M_6Br_(12)(H_2O)_6]^(2+) and [Ta_6Cl_(12)(H_2O)_6]^(3+) are correlated.

hexanuclear complexes of niobium and tantalum; magnetic and electrical properties

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