METAL-ION CONTROL OF ORGANIC-REACTIVITY - ELECTROPHILIC AND NUCLEOPHILIC REACTIONS OF COORDINATED 2-IMINOPROPANOATE

Chelate complexes derived from 2-imino carboxylato ligands contain both electrophilic and nucleophilic sites for reaction. To explore both the utility and control of these properties, reactions of the simple pyruvate imine complex [(NH3)4Co(NH=C(CH3)CO2)]2+ with a variety of polyfunctional molecules have been examined. Diethyl oxaloacetate reacts to provide a substituted pyridine, showing that the previously observed reaction of the complex with biacetyl to give a pyrroline can be varied to provide other heterocycles. Reactions with dimethyl acetylenedicarboxylate and methyl vinyl ketone, in contrast, provide branched-chain ligands via cyclization onto the metal center, the pathway for the methyl vinyl ketone reaction being confirmed by a crystal structure determination. Plausible mechanisms for the reactions are discussed in some detail.