Conformational effects on P–N–P coupling constants in diphosphinoamines and related compounds

Abstract

1 H-{31P} and 31P n.m.r. measurements on the triphosphazanes (Ph2P·NR)2PPh show that J(PNP) is +280 Hz when R = Me and 25.1 Hz when R = Et. A similar marked dependence on the R groups has been found for the diphosphinoamines, Ph2P·NR·PPhCl (R = Me, Et, Prn, Pri, and But)(+334 to –35 Hz), and this may be related to the conformations about the P–N bonds, which are influenced by the stereochemical bulk of R. 1H-{31P} INDOR experiments on the symmetrical diphosphinoamines, Ph2P·NR·PPh2(R = Me, Et, and Pri), indicatethat J(PNP) is much greater when R = Me than when R = Et or Pri.