Phosphorus–phosphorus nuclear spin coupling in tetraorganobiphosphines and some of their derivatives

Abstract

The signs and magnitudes of ³¹P^–31P and ³¹P–H spin-coupling constants in tetraorganobiphosphines RR′PPRR′ with Me, Ph, and/or Bu^t as substituents, and in their sulphides and selenides RR′P(X)P(X)RR′(X = S or Se), have been determined by ¹H-{³¹P} heteronuclear double resonance. Large variations in ¹J(³¹P-³¹P) arise as a result of changes in the phosphorus hybridization and/or effective nuclear charge, and smaller variations as a result of changes in the position of rotameric equilibrium in the gauche conformers of the biphosphines.