Contributions to the little known chemistry of trivinylphosphine and trivinylarsine

Trivinylphosphine has been prepared via an improved synthetic method (from triphenyl phosphite). Vi₃P undergoes standard quaternization only with methyl iodide to give high yields of [MeVi₃P]I. The reactions with ethyl iodide, ethyl trifluoromethanesulfonate, benzyl bromide, and vinyl bromide failed to give the analogous phosphonium salts, and insoluble polymeric products were obtained instead. Polymerization also occurs upon attempted halogenation using hexachloroethane or elemental iodine. By contrast, trivinylarsine gives the corresponding arsonium salts with MeI, EtI, and BzBr without complications. A mechanism is proposed for the observed differences in reaction behavior taking into account complementary observations from previous investigations. The activation of the vinyl functions upon quaternization of Vi₃P is also evident from the propensity of [MeVi₃P]I to the spontaneous (or base-catalyzed) addition of up to 3 equiv of methanol to give the three salts [MeVi_nP(CH₂CH₂OMe)_3-n]I (n = 1-3). The three chalkogenides Vi₃PE (E = O, S, Se) can be prepared by addition of E to Vi₃P without polymerization, and coordination to AuCl also leads to a stable complex (Vi₃P)AuCl. No reaction was observed between Vi₃P and elemental tellurium. The crystal and molecular structures of [MeVi₃P]I(CHCl₃), [MeVi₂PCH₂ CH₂OMe]I, [MeVi₃As]I, [BzVi₃As]Br, Vi₃PO, Vi₃PSe, and (Vi₃P)AuCl have been determined, and their conformational characteristics are discussed.