Abstract: | Natural abundance 13C NMR studies have been carried out on a series of organophosphorus compounds possessing P? N bonds. For the first time a one-bond temperature-dependent 13C—31P nuclear spin coupling was observed for the P-phenyl carbons in bis(N,N-dibenzylamino)phenylphosphine (0-9 Hz) and bis(N,N-diethylamino)phenylphosphine (0–2 Hz). This temperature-dependent behavior can be rationalized in terms of free rotation about the phenyl phosphorus bond with concomitant hindered rotation about the P? N bonds. A conformational preference for the nitrogen and phosphorus lone pairs to exist in the trans orientation is indicated. In the similarly substituted 5-membered heterocyclic ring compound, 1,3-dimethyl-2-phenyl-1,3-diazaphospholidine, the phenyl one-bond coupling increases to (?) 42.1 Hz and becomes temperature independent. These data suggest that 1J(PC) is very responsive to electronic effects. |