Catena-poly[[[aquabis(1H-benzimidazole-kappaN(3))cadmium(II)]-micro-phthalato-kappa(3)O,O':O"] hemihydrate]

The title compound is a polymeric complex bridged by a phthalate dianion, [[Cd(C(8)H(4)O(4))(C(7)H(6)N(2))(2)(H(2)O)].0.5H(2)O](n). The asymmetric unit contains two Cd complex units, and both Cd(II) atoms have the same distorted octahedral coordination geometry. Each phthalate dianion bridges two Cd atoms through the two terminal carboxy groups, one in a monodentate fashion and the other in a chelating mode, thus forming zigzag polymeric chains; pi-pi stacking occurs between neighboring chains. The bond angle involving the chelating carboxy group is large, but the corresponding bond distance is normal. This implies the existence of an electrostatic interaction between the Cd(II) atoms and the carboxy groups.