Synthetic, nuclear magnetic resonance and X-ray crystallographic studies of conformations of polyorganophosphorus compounds

Abstract

Addition reactions between ERH₂(E = P or As; R = Ph, CH₂CH₂CN, Bu or C₆H₂Bu^t₃-2,4,6) and (Ph₂P)₂CCH₂ or (Ph₂P)₂CCHR′(R′= H or Me) yield the triphosphines (Ph₂P)₂CHCHR′ERH and the pentaphosphines [(Ph₂P)₂CHCH₂]₂ER and (Ph₂P)₂CHCH(Me)P(Ph)CH₂CH(PPh₂)₂. The two- and three-bond ³¹P–³¹P nuclear spin-spin coupling constants in these vary substantially with the bulk of substituents on or near phosphorus, probably as a result of conformation differences. The structures of (Ph₂P)₂CHCH₂PHPh, (Ph₂P)₂PCHCH₂PH(C₆H₂Bu^t₃-2,4,6) and [(Ph₂P)₂CHCH₂]₂PPh have been determined by X-ray diffraction and suggest that each of these species adopts a conformation in solution that is very similar to that found in the solid state.