Mixed-ligand complexes by reaction of metal carbonates and carboxylic acids under hydrothermal conditions

INOR 41

Graciela C. Díaz de Delgado, diaz@ula.ve, Jines E. Contreras, Ali Bahsas B, and José Miguel Delgado Q. Departamento de Química, Universidad de Los Andes, Facultad de Ciencias, Apdo. 40, La Hechicera, 5101 Mérida, Venezuela
The synthesis of new hybrid organic-inorganic materials continues to be an important area of research. Many of these materials are prepared under hydrothermal conditions using a metal source such as a carbonate or a hydroxide, and an organic compound such as a carboxylic acid. These processes often induce rearrangements, cleavage, decomposition, among other reactions, which may prevent the formation of a desired complex and/or lead to a completely different material. As part of our attempts to prepare Ba and Ca complexes of itaconic acid (methylenesuccinic acid) via hydrothermal routes, we obtained from the reaction with BaCO3 a mixed-ligand compound, Ba5[(Citraconate)2(2,3-dimethylfumarate)]. When the reaction was carried out with CaCO3, Ca-citramalate was obtained. Solution NMR indicated the presence of residual citraconate, mesaconate, itaconate, 2-(hydroxymethyl)-succinate, and traces of citramalate anions in the solid resulting from the reaction with BaCO3. For the Ca reaction, 2,3-dimethylfumarate and 5-oxotetrahydrofuran-3-carboxylate are also obtained.