Tris(2,6-dimethoxyphenyl)phosphine sulfide reacted with alkyl iodides or bromides under mild conditions to give stable alkylthiophosphonium salts, which reacted with thiols at room temperature in the presence of a catalytic amount of tris(2,6-dimethoxyphenyl)phosphine to give the tertiary phosphonium salt and unsymmetrical disulfides.