Competition between different nucleophilic sites belonging to the same Lewis bases. Part I. Aminophosphines towards borane

Abstract

The nature of the donor–acceptor interactions in aminophosphine–borane adducts has been investigated by means of the chemical behaviour of the borane group and ¹H, ¹¹B, and ³¹P n.m.r. spectra. The phosphorus atom appears to be a better acceptor than nitrogen towards BH₃ when these two donor atoms are linked together, such as in Me₂NPMe₂ and (Me₂N)₂PMe. However, when these two atoms are separated by a methylene bridge, as in (Et₂NCH₂)₃P, borane co-ordinates with nitrogen rather than with phosphorus. The results are explicable in terms of multiple bond behaviours and steric hindrance.