Trends in the nitrogenoxygen stretching frequency of 4-substituted pyridine N-oxide coordination compounds

Abstract

Trends in the nitrogenoxygen stretching frequency, ν NO, for twenty-four series of 4-substituted pyridine N-oxide complexes have been investigated and compared. It was found that the complexes fall into several general categories based on the correlation of ν NO and Δν NO (the decrease in ν NO of the ligands upon coordination) with σ PyO substituent constants. The data suggest that the trends depend significantly on the effective charge of the central metal ion but that stereochemistry, steric effects, and the previously proposed π-bonding effects also contribute.