Interdependence of phosphorus-31–selenium-77 NMR coupling constants in bicyclic phosphorus selenide compounds

Abstract

Bicyclic compounds exo,exo-α-P₄Se₃X₂ and exo,exo-α-P₄Se₃XI (X = CN, NMePh or NPrⁱ₂) and endo,exo-α-P₄Se₃(CN)₂ have been made in solution and their ³¹P and ⁷⁷Se NMR spectra completely analysed. Ab initio calculations of ³¹P and ⁷⁷Se NMR shieldings in exo,exo- and endo,exo-α-P₄Se₃(CN)₂ and in exo,exo-α-P₄Se₃(CN)I confirmed these assignments. In an unsymmetric compound exo,exo-α-P₄Se₃XI the twelve ³¹P–⁷⁷Se NMR coupling constants have values related to those in the corresponding symmetric compounds exo,exo-α-P₄Se₃X₂ and exo,exo-α-P₄Se₃I₂ by simple rules, useful for predicting couplings in exo,exo-α-P₄Se₃X₂ when the spectra of exo,exo-α-P₄Se₃XI and exo,exo-α-P₄Se₃I₂ have already been analysed.