Tris(monochloropheny1)phosphines 1-3 and tris(2,6-dichlorophenyl)phosphine (4) were prepared. The X-ray structure of 4 was determined. Electrochemical oxidation of 1-4 showed a good correlation between anodic peak potentials and Hammett d parameters in homologous series of substituted triarylphosphines. The ESR spectrum of radical-cation 4'+ was composed of a large doublet with the highest known coupling constant for triarylphosphoniumyl radicals (Ap = 366 G at -30 "C).