Study of the aqueous reactions of metallic ions with benzenetetracarboxylate ions - Part 1. Crystal structures of compounds of the types [M(H2O)(6)][C6H2(COO)(2)(COOH)(2)] (M = Mn, Co and Ni) and Ni(H2O)(5)(mu-C6H2(COO)(4))Ni(H2O)(5)center dot 6H(2)O

The reactions of several divalent transition metals with 1,2,4,5-benzenetet racarboxylate ions were studied in aqueous solution. Mn(II), Co(II) and Ni( II) produced ionic products of formula [M(H2O)(6)][C6H2(COO)(2)(COOH)(2)]. The three compounds were characterized by crystallographic methods. The res ults have shown that the three crystals are isostructural and that they bel ong to the monoclinic C2/c space group. The metal atom and two O atoms (fro m two aqua ligands) are located on a two-fold axis, while the other four aq ua ligands are located in general positions. The anions contain an inversio n center. The two hydrogens on the carboxylic functions form intramolecular H bonds with the carboxylate groups. The average M-OH2 bond distances are 2.181(1) Angstrom for Mn(II), 2.092(1) Angstrom for Co(II) and 2.056(1) Ang strom for Ni(II). The ions are linked together by extensive H bonds. With t he Ni salt, a dinuclear species, containing a bridging benzenetetracarboxyl ato ligand was synthesized and characterized by X-ray diffraction. The comp ound Ni(H2O)(5)(mu-C6H2(COO)(4))Ni(H2O)(5). 6H(2)O contains an inversion ce nter in the center of the phenyl ring. The average Ni-OH2 distance is 2.071 0(8) Angstrom and the sixth Ni-O bond is 2.0356(7) Angstrom. The Ni ... Ni distance is 11.360(2) Angstrom. The crystal is stabilized by a very elabora te H-bonding system forming a H-bonded three-dimensional network. (C) 2000 Elsevier Science S.A. All rights reserved.