STRUCTURES OF SODIUM COMPLEXES OF CITRACONIC ACID. Graciela Daz de Delgado, Teresa Gonzlez, and Alexander Briceo V. Laboratorio de Cristalografa, Departamento de Qumica, Facultad de Ciencias, Universidad de Los Andes, Mrida 5101, Venezuela.

The structures of two sodium complexes of citraconic acid are presented in this paper. Sodium citraconate monohydrate (1) and sodium hydrogen citraconate (2) were obtained by slow evaporation of H₂O/DMSO solutions containing citraconic acid and sodium carbonate in molar ratios of 1:1 and 2:1 respectively. Crystal data for (1): Monoclinic, C2/m, with lattice parameters a=10.967(3), b=6.811(2), c=10.207(3), =88.23(2), Z=4. The refinement on F² converged at wR²=0.1000, R=0.0337, S=1.084 for 862 reflections with I>2(I). Crystal data for (2): Monoclinic, P2₁/c, with lattice parameters a=12.003(4), b=5.395(2), c=10.213(4), =111.12(2), Z=4, wR²=0.1927, R=0.0761, S=1.098 for 953 reflections with I>2(I).

Compound (1) is a coordination polymer where the two sodium atoms display different coordination geometries. One sodium atom is pentacoordinated with Na-O distances in the range 2.278(2)-2.596(2) while the other is coordinated to six oxygen atoms with Na-O distances between 2.362(1) and 2.546(1). In compound (2) layers of Na atoms with citraconate moieties above and below the plane stack along the a-axis. The sodium atom is hexacoordinated with Na-O distances of 2.329(2) to 2.596(2).

This work was supported by CONICIT, Grants NM-18 and S1-9500038, and by CDCHT-ULA Grant C-755-95-08-F.