Carbon-13 nuclear magnetic resonance spectra of rhodium carbonyl complexes

Abstract

The 13C NMR spectra of a series rhodium carbonyl complexes were measured. An approximate correlation of δ( 13CO) chemical shifts with carbonyl group stretching frequencies ν(CO) was observed. For square planar complexes the variations in ν(CO) parallel that of the coupling constants 1 J(RhC). The oxidative addition to planar rhodium(I) complex with formation of octahedral rhodium(III) complex results in opposite trends for ν(CO) and J. The greater ν(CO) value reflects the diminished electron density on the central atom and a lower coupling constant is due to the reduced contribution of the rhodium 5 s orbital in the RhCO bond.