The chemistry of some alkylcobaloxime complexes



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Texas Tech University


The synthesis of amino acids and their analogues (e.g., glycine or N-phenylglycine, etc.), employing a bis-(dimethylglyoximato) cobaltate as a template, is described. Carbon bonded N-methylaniline and Nmethylphthalimide adducts of cobaloxime with pyridine, occupying a sixth coordination position of the cobalt atom, were prepared and isolated. In the presence of a chemical reducing agent, these cobaloxime complexes were found to undergo reductive cleavage of the cobalt-carbon bond and lead to the formation of an amino acid in the presence of carbon dioxide. The amino acids thus produced were characterized by TLC, GC, NMR and ultraviolet spectroscopy.

Methylcobaloxime, with acetonitrile in the basal (sixth) coordination position of the cobalt atom, was prepared and isolated. This cobaloxime complex was found to undergo ligand substitution, in benzene solution, liberating free acetonitrile by THF, with and without the presence of crown ethers, were investigated. The rate constants obtained without the presence of crown ethers were found to be inversely dependent on the concentration of THF. The presence of crown ethers in the reaction mixture resulted in a retarded rate of the ligand substitution. The causes of the retardation effect on the reaction rates are discussed. The study was carried out at 25 C and the rate of the ligand substitution were monitored by observing the increase in the visible absorption that occurred at 455 nm.



Ligands, Complex compounds, Vitamin B12, Organocobalt compounds, Amino acids