Preparation and crystal structure of tetraaqua-bis(hydrogenopyridine-2,3(di carboxylate)bis(pyridine-2,3-dicarboxylate)hexa silver(I) [Ag-6(C7H4NO4)(2)(C7H3NO4)(2)(H2O)(4)](n)

The title compound was precipitated by the action of freshly prepared Ag2O on an aqueous solution of pyridine-2,3-dicarboxylic acid. The white compound was redissolved in hot water and crystals suitable for X-ray diffraction study were grown. The crystal is a polymeric network; five-membered chelate rings (-C-N-Ag-O-C-) and dimeric units (AgOCO')(2) sequenced in two types of similar chains linked by Ag-Ag bonds and short intermolecular hydrogen bonds are presented simultaneously. The four Ag atoms of the asymmetric unit show two different environments. Ag(1) and Ag(2), sitting on a symmetry centre, are each included in two chelating rings. So, Ag(1) and Ag(2) are in four-coordinated planar environments: Ag(1)-N(21) = 2.166(5), Ag(1)-O(24) = 2.705(4), Ag(2)-N(11) = 2.172(4), Ag(2)-O(11) = 2.706(5) Angstrom, N(21)-Ag(1)-O(24) = 67.7(2), N(11)-Ag(2)-O(11) = 68.4(2)degrees. Ag(3) and Ag(4) are included in eight-membered rings, (AgOCO')(2) with bipyramidal trigonal arrangement constituted by two Ag atoms [Ag(3)-Ag(3(ii)) = 2.843(2), Ag(3)-Ag(4(i)) = 3.090(2), Ag(4)-Ag(4(v)) = 2.894(1) Angstrom, two oxygen carboxylic atoms [Ag(3)-O(23) = 2.271(5), Ag(3)-O(24(ii)) = 2.245(4), Ag(4)-O(12(v)) = 2.236(6), Ag(4)-O(11) = 2.242(6) Angstrom] and one aqueous oxygen atom [Ag(3)-O(wl) = 2.329(6), Ag(4)-O(w2) = 2.399(5) Angstrom]. The H carboxylic hydrogen atoms of the hydrogenopyridine-2,3-dicarboxylate ligands being split between two carboxylate groups are involved in short intermolecular hydrogen bonds between two carboxylic groups: O(13)...O(22(ii)) = 2.459(4) Angstrom. Copyright (C) 1996 Elsevier Science Ltd