Synthesis and Properties of Two Bis(1-Hydroxyethane-1,1-Diphosphonato(2-))nickelate(II) Ammonium Hydrates: Crystal and Molecular Structures of (NH4)2[Ni{CH3COH(PO3H)2}2(H2O)2] • 7H2O

Two hydrates of the ammonium salt of Ni(II) complex (NH(4))(2)[Ni(H(2)L)(2)] center dot nH(2)O, where H(2)L = MeCOH(PO(3)H)(2)(2-), n = 9 (I) and 3 (II) are obtained. Compound I is stable in contact with an aqueous solution, but in air it is spontaneously dehydrated to II. Complex II forms a metastable solution and does not change in air. The structure of I was determined by X-ray diffraction analysis. In the anionic complex, the Ni atom has a regular octahedral coordination due to four O atoms of two bidentate chelating ligands H(2)L and two O(w) atoms of water molecules cis-positioned to each other (Ni-O, 2.044-2.085 angstrom). In the crystals, the anionic complexes, ammonium cations, and molecules of water of crystallization are linked together by a branched network of hydrogen bonds.