Poly[di-µ(3)-hy-droxy[µ(4)-5-(4-carb-oxy-phen-yl)pyridine-2-carboxyl-ato-κ(5)N,O(2):O(2'):O(4):O(4')]dicadmium].

The asymmetric unit of the title polymeric complex, [Cd(2)(C(13)H(7)NO(4))(OH)(2)](n), consists of two independent Cd(II) atoms, one 5-(4-carb-oxy-phen-yl)pyridine-2-carboxyl-ate ligand and two hy-droxy groups. One Cd(II) atom is six-coordinated by two O atoms from two ligand mol-ecules and by four µ(3)-OH groups in a distorted trigonal-prismatic geometry. The other is five-coordinated by one N and two O atoms from two ligands and by two µ(3)-OH groups, forming a distorted square-pyramidal geometry. The two independent Cd(II) atoms are connected by the ligand mol-ecules and the OH groups into a three-dimensional framework. O-H⋯O hydrogen bonds between the OH groups and the carboxyl-ate O atoms are observed.

catena-Poly[[dichloridozinc(II)]-µ-1,1'-(butane-1,4-di-yl)diimidazole-κN:N].

The title compound, [ZnCl(2)(C(10)H(14)N(4))](n), is a coordination polymer consisting of zigzag chains propagating in [001], in which the metal cation exhibits a distorted tetrahedral ZnCl(2)N(2) coordination. Adjacent chains are linked by inter-molecular C-H⋯Cl hydrogen bonds, forming a three-dimensional supra-molecular network.

A polymorph of diaqua-bis(pyrazine-2-carboxyl-ato-κN,O)copper(II).

The title compound, [Cu(C(5)H(3)N(2)O(2))(2)(H(2)O)(2)], is a new polymorph of the previously reported compound [Klein et al. (1982 ▶). Inorg. Chem.21, 1891-1897]. The Cu(II) atom, lying on an inversion center, is coordinated by two N atoms and two O atoms from two pyrazine-2-carboxyl-ate ligands and by two water mol-ecules in a distorted octa-hedral geometry with the water mol-ecules occupying the axial sites. Inter-molecular O-H⋯O, O-H⋯N and C-H⋯O hydrogen bonds connect the complex mol-ecules into a two-dimensional layer parallel to (10), whereas the previously reported polymorph exhibits a three-dimensional hydrogen-bonded network.