USE OF SOLID-STATE C-13 NMR-SPECTROSCOPY TO QUANTIFY THE DEGREE OF ASYMMETRY OF BONDING FOR SEMIBRIDGING CO GROUPS IN IRON CARBONYL-COMPLEXES

The solid-state C-13 NMR spectra of some substituted iron carbonyl complexes have been analyzed to give values for the carbonyl carbon chemical shift tensor components. It is shown that the lowest frequency tensor component and the chemical shift anisotropy correlate with the degree of bonding asymmetry in double-bridging carbonyl groups, whereas the C-13 isotropic chemical shift does not correlate. The correlations are proposed to form the basis for a method of estimating iron-carbon bond lengths for mu-2-CO groups in this type of complex.