Studies of nitrogen-15–phosphorus-31 nuclear spin–spin coupling by heteronuclear magnetic double resonance

Abstract

The signs and magnitudes of ¹J(³¹P–¹⁵N), ²J(³¹PNH), ³J(¹⁵NPCH), and certain other coupling constants, and phosphorus-31 and nitrogen-l 5 chemical shifts, have been determined in 24 organophosphorus compounds with P–N bonds and enriched in nitrogen-15. The coupling ¹K(PN) has substantial negative values in phosphorus(III) compounds and becomes more positive with values near zero when phosphorus is four-co-ordinate. The behaviour of ²J(³¹PNH) is consistent with the hybridization of nitrogen being close to sp² in these species. and this is attributed to p_π–d_π overlap with phosphorus and/or p_π–p_π overlap with N-phenyl groups.