Synthesis and crystal structure of Ni(VO3)(2)center dot 4H(2)O and alpha-Ni(VO3)(2)center dot 2H(2)O

Two new nickel metavanadate hydrates, NL(VO3)(2). 4H(2)O and alpha-Ni(VO3)( 2). 2H(2)O, have been synthesized using a "chimie douce" process; their cry stal structures have been solved from single-crystal X-ray diffraction data . The tetrahydrate Ni(VO3)(2). 4H(2)O crystallizes in the monoclinic space group C2/c with a unit cell of dimensions a = 12.969(5)Angstrom, b = 9.817( 3) A, c = 6.880(2) Angstrom, beta = 112.14(3)degrees; Z = 4; the structure was determined from 1055 independent reflections and refined until R = 0.02 4 and R-w = 0.034, An orthorhombic cell has been found for the dihydrate al pha-Ni(VO3)(2) 2H(2)O: a = 5.530(1)Angstrom, b = 10.621(10) Angstrom, c = 1 1.756(5) Angstrom, Z = 4, space group Pnma; the structure was determined fr om 1201 independent reflections until R = 0.017 and R-w = 0.018, The struct ures of the two materials mainly differ in the vanadium environment in the (VO3)(n)(n-) metavanadate chains. They are constituted of edge-linked VO5 s quare pyramids in the tetrahydrate and from vertex-linked VO4 tetrahedra in the dihydrate, As the hydrogen atoms were localized in these two compounds , all the hydrogen bonds existing in these structures were clearly evidence d. (C) 2000 Acdemic Press.