A study of electronic transmission in cobalt(III) dimethylglyoxime complexes by nuclear magnetic resonance spectroscopy

Abstract

The n.m.r. spectra of a number of cobalt(III) dimethylglyoxime complexes of the type Co(DH)₂LX where L is triphenylphosphine or pyridine have been measured. The chemical shifts of the dimethylglyoxime methyl hydrogens and the hydrogen-bonded hydrogens depend on the axial ligands and a correlation has been found between the chemical shift of the methyl hydrogens and the Hammett σ_para-function of the ligand X. This correlation is interpreted as lending support to the suggestion that the ground-state cis-effect in these complexes reflects changes in the electron density in the cis-ligand.