Use of solid-state carbon-13 NMR spectroscopy to quantify the degree of asymmetry of bonding for semibridging carbonyl groups in iron carbonyl complexes

The solid-state {sup 13}C 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 {sup 13}C 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}{sub 2}-CO groups in this type of complex. 1 table, 4 figs., 30 refs.