A new two-dimensional molybdenum(V) nickel phosphate built up of [H18(Mo16O32)Ni16(PO4)26(OH)6(H2O)8]18- wheels

The new molybdenum(V) nickel phosphate Na6Ni6[(Mo2O4)(8)Ni-16(H2PO4)(4)(HPO4)(10)(PO4)(12)(OH)(6)(H2O)(8)].66H(2)O (1) was synthesized hydrothermally. The structure (orthorhombic, space group Cccm; a = 23.999(4), b = 36.595(6), c = 20.445(4) Angstrom) was solved from single-crystal data. The framework structure of 1 consists of anionic inorganic sheets formed by the linkages of large polyoxomolybdate rings via nickel(II) octahedra. Charge-compensating sodium atoms are interleaved between the sheets. Magnetic studies of compound 1 revealed that among the 22 nickel(II) centers, 10 are interacting. The chi(M)T = f(T) curve can be fitted using the dinuclear expression appropriate to the HDVV isotropic exchange Hamiltonian H = -2JS(1).S-2, with S-1 = S-2 = 1 and J = -24.1 cm(-1), showing that nickel is antiferromagnetically coupled within Ni-2 pairs.