Gold(I) and palladium(II) complexes containing the functionalized ylides triarylphosphonium cyanomethylide or 2-cyanoethylide (R₃P=CHR', R'= CN, CH₂CN)

The coordination properties of ylides R₃P=CHCN and R₃P=CHCH₂CN were studied. Ylide R₃P=CHCN reacts with [AuCl(tht)] (molar ratio 1:1, tht=tetrahydrothiophene) to give [AuCl{CH(PPh₃)CN}] (1). Dinuclear complexes [(AuL)₂-{μ-C(PR₃)CN}]ClO₄ · nH₂O (n = 1, L = PPh₃, R = Ph (2a) or Tol (= 4-MeC₆H₄) (2b); n = 0, R = Tol, L = P(pmp)₃ (2c; pmp = 4- MeOC₆H₄ or AsPh₃ (2d)) are the products of reactions between phosphonium salts (R₃PCH₂CN)ClO₄ (R = Ph or Tol) and [Au(acac)L] (molar ratio 1:3, L = PPh₃ or P(pmp)₃; acacH = acetylacetone). The reaction of [Au(acac)PPh₃] with (Ph₃PCH₂CH₂CN)ClO₄ (Au/P 2-5) gives the mononuclear complex [Au{CH(PPh₃)CH₂CN}(PPh₃)]ClO₄ · 0.5 H₂O (3). Complexes 2b or 2c react with [Au(acetone)L]ClO₄ (molar ratio 1:1, L = PPh₃ or P(pmp)₃), prepared in situ from [AuCl(L)] and AgClO₄ in acetone, to give the corresponding trinuclear derivatives [(AuL)₂{μ₃-{C(PTol₃)CN}(AuL)}](ClO₄)₂ (L = PPh₃ (4a) or P(pmp)₃ (4b)]. We attempted unsuccessfully to prepare single crystals of 4a or 4b or of the triflate salt [{Au(PPh₃)}₂{μ₃{C(PTol₃)CN}(AuPPh₃)}] (TfO)₂ · H₂O (4a'), obtained by reacting 4a with 2 equiv. of KCF ₃SO₃. In complexes 2 and 4, two new types of coordination of the ylides R₃P = CHCN are present. Attempts to coordinate three AuL groups to the N-atom of (R₃PCCN)^- induced by aurophilicity (see A and B) were unsuccessful. The reaction between PdCl₂ and R₃P=CHCN (molar ratio 1:2) gives trans-[PdCl₂{CH(PTol₃)CN}₂] (5).