[(C6H10)(NH3)2][Ni(H2O)4C6H2(COO)4]•4H2O -: A coordination polymer with the chain-like polyanion {Ni(H2O)4[C6H2(COO)4]2-}n

Triclinic single crystals Of [(C6H10)(NH3)(2)]-[Ni(H2O)(4)C6H2(COO)(4)]center dot 4H(2)O have been prepared in aqueous solution at 55 degrees C. Space group P (1) over bar (Nr. 2), a = 691.23(6), b = 924.84(5), c 1082.43(7) pm, alpha = 74.208(6)degrees, beta = 75.558(7)degrees, gamma = 68.251(6)degrees, V = 0.60985(7) nm(3), Z = 1. The Nickel(II) species, located on a crystallographic inversion centre, is coordinated in a trans-octahedral fashion by two oxygen atoms stemming from the centrosymmetric pyromellitate anions and four from water molecules (Ni-O 205.82(12) - 208.11(13) pm). The connection between Ni2+ and [C6H2(COO)(4))](4-) leads to infinite chain-like polyanions extending parallel to [10(1) over bar] with {Ni(H2O)(4)[C6H2(COO)(4)](2-)}(n) composition. [(C6H10)(NH3)(2)](2+)-cations are accomodated between the chains, compensating for the negative charge of the polyanions. Thermogravimetric analysis in air showed that the loss of water of crystallisation occurs in two steps between 102 and 206 degrees C, corresponding to the loss of 6 and 2 water molecules per formula unit, respectively. The dehydrated sample was stable between 206 and 353 degrees C. Further decomposition yielded nickel(II) oxide (NiO).