Preparation and properties of tertiary p-alkylarylphosphines containing straight-chain alkyl groups

Abstract

A series of tris(p-alkylaryl)phosphines with straight chain alkyl groups, P(p-C₆H₄–C_nH_2n+1)3 where n= 2–9, have been prepared by reaction of phosphorus trichloride with the Grignard reagent derived from the corresponding p-bromoalkylbenzene. When n= 2 and 3 the phosphines are crystalline solids, but for n > 3 they are viscous oils up to n= 9, which is a waxy solid. The phosphines have been characterised by microanalysis, and i.r., ¹H and ³¹P n.m.r., and mass spectrometry. The p-substituted-arylphosphines are more sensitive than triphenylphosphine to air; aerial oxidation converts them exclusively into the corresponding phosphine oxide, in contrast to trialkylphosphines which are oxidised to a complex mixture of products. The complexing ability of the new phosphines (PAr₃) is demonstrated by their ready displacement of 1,5-cyclo-octadiene (cod) from [M(cod)Cl₂](M = Pd and Pt) to yield trans-[Pd(PAr₃)₂Cl₂] and cis-[Pt(PAr₃)₂Cl₂], respectively.