Studies of phosphorus–phosphorus nuclear-spin coupling in species with phosphorus–nitrogen bonds

Abstract

¹ H-{³¹P} double-resonance experiments have been used to study 34 organophosphorus spacies with a P–N–P skeleton. The geminal ³¹P–³¹P coupling constant is large and positive in derivatives of three-co-ordinate phos-phorus and is increased by bulky or electronegative substituents on phosphorus. The results for several pairs of diastereoisomers, and also the temperature dependence, indicate a strong conformational dependence of the coupling which is related to the relative orientation of the lone pairs on phosphorus. In spacies with at least one four-coordinate phosphorus atom this last feature is absent, and the coupling constant is much smaller.