Structural variations in the complexes of cadmium(II), hexamethylenetetramine, and 2-, 3- and 4-nitrobenzoates

Four new cadmium(II)-)–hexamethylenetetramine (hmt) complexes {[Cd(2-nbz)2(μ2-hmt)(OH2)]·2H2O}n (1), [Cd(3-nbz)2(hmt)2(OH2)2]·2(3-nbzH) (2), [Cd(3-nbz)4(μ2-hmt)]n (3) and {[Cd2(4-nbz)4(μ2-hmt)2(OH2)2]·H2O}n (4) with three isomeric nitrobenzoates, [2-nbz = 2-nitrobenzoate, 3-nbz = 3-nitrobenzoate and 4-nbz = 4-nitrobenzoate] have been synthesized and structurally characterized by X-ray crystallography. Their identities have also been established by elemental analyses and IR studies. Complex 2 is a monomer. Complexes 1, 3 and 4 are 1D chains, with varied stereo arrangements. The presence of coordinating water and non-coordinating 3-nbzH molecules change the stereo arrangement of complex 2 from that of 3, which is devoid of both these types of molecules. In 3, two nitrogen atom of hmt coordinate to Cd(II) ion with N-–Cd-–N angle 114.4°. Various weak forces, i.e. π–π, CH–π and cation–π interactions play a key role in stabilizing the observed structures. This series of complexes demonstrates that although the nitro group does not coordinate to the metal center, its presence at the 2-, 3- or 4- position of the phenyl ring has a striking effect on the dimensionality as well as the structure of the resulted coordination polymers, probably due to the participation of the nitro group in cation⋯π and/or C-–H⋯π interactions.