Poly[bis(benzimidazole-N³)copper(II)-μ-acetylenedicarboxylato-O:O'-μ-aqua] and Poly[bis(benzimidazole-N³)copper(II)-μ-aqua-μ-fumarato-O:O']

The title compounds, poly[bis(benzimidazole-N³)copper(II)-μ-acetylenedicarboxylato-O:O′-μ-aqua], [Cu(C₄O₄)(C₇H₆N₂)₂(H₂O)], (I), and poly[bis(benzimidazole-N³)copper(II)-μ-aqua-μ-fumarato-O:O′], [Cu(C₄H₂O₄)(C₇H₆N₂)₂(H₂O)], (II), have been synthesized, and their crystal structures determined by single-crystal X-ray diffraction at room temperature. Structures (I) and (II) are very similar. In both structures, the centrosymmetric Cu atoms are bridged by the dicarboxylic acid ions in a bis-monodentate fashion, forming polymeric chains. The Cu...Cu intrachain distances are 9.546 (1) Å in (I), and 9.276 (1) Å in (II). These chains are connected by bridging H₂O molecules, which are located on the twofold axes by Cu–H₂O bonds of 2.593 (1) Å in (I), and 2.668 (1) Å in (II). The Cu...Cu distances in the –Cu–H₂O–Cu– chains are 5.090 (1) and 5.199 (1) Å, in (I) and (II), respectively. The base of the elongated octahedron of the Cu^II atoms is formed by two short Cu–O and two short Cu–N bonds [Cu–O = 1.970 (1) and 1.946 (2) Å, Cu–N = 2.005 (2) and 2.016 (2) Å, in (I) and (II), respectively]. The modes of coordination of the carboxylate groups, and of the hydrogen bonds, are discussed. The isostructurality of the title compounds and of their previously investigated homologue, (III), has been analysed.

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