DFT study of reductive functionalization in cis and trans cobalt-methyl-bipyridine complexes

Density functional theory (DFT) calculations were utilized to study the reductive functionalization (RF) of a bipyridine Co(III)-methyl complex, an integral step in metal-catalyzed hydrocarbon functionalization. In general, for the different X co-ligands modeled, ground and transition states were computed to be cis geometric isomers and singlet spin states, thus implying RF with these 3d metal complexes will proceed without impediment from large amplitude geometric changes or spin forbidden reactions. Barriers for nucleophilic attack (NA) by hydroxide were also compared with Co-Me bond homolysis, and the former revealed to be lower by a substantial free energy margin. Furthermore, the differences between the NA free energy barriers and the bond dissociation free energies (BDFE) varied for each ligand, indicating that the X co-ligands, although cis to the cobalt-methyl-nucleophile active site, can have significant impact in determining which catalysts will prove desirable. Overall, this research suggests that the bipyridine Co(III) complexes studied here are worthy of experimental studies.