Synthesis and structure of d-metal complexes with 2,3,5,6-tetraoxo-4-nitropyridine: Crystal structure of Ni(H2O)(6)(C5HO6N2)(2) center dot 2H(2)O

Crystal hydrates of nickel(II) perchlorate and cobalt(II), copper(II), and zinc(II) chlorides react with ammonium 2,3,5,6-tetraoxo-4-nitropyridinate (NH4)(2)(C5HO6N2)(2) to produce the M(H2O)(6)(C5HO6N2)(2) . 2H(2)O complexes. The crystal structure of Ni(H2O)(6)(C5HO6N2)(2) . 2H(2)O has been determined by X-ray single-crystal diffraction. In the course of complex formation, complex cations [Ni(H2O)(6)](2+) are substituted for the ammonium cations in the organic salt, the organic anions are linked with the coordinated water molecules by O...H-O hydrogen bonds, and the dimers of 2,3,5,6-tetraoxo-4-nitropyridinate anions are spatially rearranged so that they cease to be charge-transfer complexes as in the initial (NH4)(2)(C5HO6N2)(2) salt