Solid state 13C CP-MAS NMR spectra of iron (alkyne) carbonyl compounds

Abstract

The solid state 13C NMR spectra of a series of iron (alkyne) carbonyl complexes, enriched in 13C at the carbonyl groups, have been obtained using 13C-{ 1H} cross-polarisation (CP) and slow magic angle spinning (MAS). In general, more resonances are observed from the solid state than from samples in solution; this may be due either to crystal packing effects lifting the degeneracy of certain signals or to a slowing of carbonyl fluxionality in the solid state. The intensities of the spinning side bands in the 13C spectra have been used to derive values for the components of the 13C shielding tensor. The component of the shielding tensor assigned to the CO bond axis (σ 33) is sensitive to the bonding of the CO group, i.e. whether it is a terminal or asymmetrically bridging group.