Structure and Solid State Behavior of Metal Complexes of Dicarboxylic Acids: Aqua (Cis-4-Cyclohexene-1,2-Dicarboxylate) Cobalt (ii) Monohydrate. Graciela Díaz de Delgado, Belkis M. Ramírez, and William O. Velásquez, Departamento de Química, Facultad de Ciencias, Universidad de Los Andes, Mérida 5101, Venezuela

Metal complexes of unsaturated carboxylic acids provide different structural environments to study the solid state behavior of the potentially reactive organic moiety.

Aqua (cis-4-cyclohexene-1,2-dicarboxylate) cobalt (II) monohydrate was prepared by slow evaporation of an aqueous solution containing cis-4-cyclohexene-1,2-dicarboxylic acid and CoCO₃ in a molar ratio of 1:1. Light-red plates grew in the solution over a period of one month. The compound is monoclinic, P2₁/c, with lattice parameters a=9.329(2), b=5.876(1), c=17.970(3)Å, (=94.89(1)(, Z=4, wR²=0.1094, R=0.0440, S=1.095 for 1790 reflections with I>2### (I). The Co atom is six-coordinated in a relatively undistorted octahedral environment. The Co-O distances range from 2.060(2) to 2.143(2) Å. The carboxylate groups provide a bridge between two different metal atoms. The structure consists of zig-zag chains which run parallel to the b-axis and join through the carboxylate groups to form corrugated layers. These layers stack along the a-axis to complete the structure.

TG-DTG measurements from 20 to 750(C show that the material suffers continuous decomposition over the temperature range studied. Four weight loss processes take place with approximate peak temperatures of 120, 190, 300, and 400(C, corresponding to endothermic transitions in the DSC curve.

This work was possible thanks to grants NM-18 Programa de Nuevas Tecnologías and S1-95000938 from CONICIT, and by grant C-727-95-08-A from CDCHT-ULA.