Chemical shift effects in the 13C-NMR spectra of [(C5H5)(CO)2FeII]-substituted cyclohexanes, dioxanes and tetrahydropyrans

A set of empirically derived 13C-NMR chemical shift additivity constants have been calculated for the Fp-substituent on cyclohexane, tetrahydropyran and dioxane rings. These were tested against a series of alkyl substituted Fp-complexes. These parameters prove to be highly reliable; the calculated and experimental chemical shifts are within ±1 ppm. The parameters vary greatly between ring systems. One explanation for the differences relates to changes in conformation about the bond connecting the Fp-group to the various rings.