Novel Inorganic Coordination Polymers Based on Cadmium Oxalates

Three new cadmium oxalate coordination polymers, I-III, with extended layered structures have been synthesized in the presence of imidazole. While I was prepared by the reaction between imidazolium oxalate and Cd, II and III were synthesized from their constituents using hydrothermal methods. [Cd(C2O4)(C3N2H4)]infinity (I): monoclinic, space group P21/c (no. 14), a=8.7093(1) ?, b=9.9477(3) ?, c=8.4352 ?, beta=93.796(1)?, Z=4; [Cd(C2O4)2(C3N2H4)3(H2O)]infinity (II): monoclinic, space group P21/c (no. 14), a=7.8614(2) ?, b=14.9332(3) ?, c=15.9153(4) ? beta=94.587(1)?, Z=4; [Cd(C2O4)2 (C3N2H4)3(H2O)]infinity (III): monoclinic, space group P21/c (no. 14), a=11.844(2) ?, b=9.066(1) ?, c=18.583(2) ?, beta=103.84(2)?, Z=4. While the structure of I is made from CdO5N distorted octahedra linked with oxalate, II and III are built-up from CdO6N, CdO5N2 distorted pentagonal bi-pyramids connected to oxalate units. The framework formulas of II and III are identical and their structures closely related. In all the cases, the networking between the Cd-O/N polyhedra and oxalates give rise to layered architectures with the amine molecules pointing in a direction perpendicular to the layers (in the inter-lamellar region). The difference in the linkages between the oxalates and the Cd atoms in I-III, produces unusual Cd-O-Cd one-dimensional chains, which have been observed for the first time.