Spectroscopy, electrochemistry, and nucleophilicity of nickel and cobalt complexes of 2′-pyridine carboxaldehyde 2′-pyridyl hydrazone (papyH)

Nickel and cobalt complexes of pyridine-2-carboxaldehyde-2′-pyridylhydrazone (papyH) and N-methyl(pyridine-2-carboxaldehyde-2′-pyridyl-hydrazone) (papyMe) have been fully characterized through electrochemistry, titration, and alkylation with methyl iodide and compared with existing data on zinc and iron complexes. Both rate constants for alkylation and ligand pKa depend on the coordinated metal and can be understood based on the influence of d electrons on the ligand molecular orbitals.