Synthesis of dinuclear gold-(I), -(II), and -(III) complexes containing ylide ligands [(RO2C)CHPPh2CH(CO2R)]–(R = Me or Et) and trinuclear gold(I) complexes containing ylide ligands [(RO2C)CPPh2CH(CO2R)]2–(R = Me or Et)

Abstract

The complexes [Au₂{µ-[CH(CO₂R)]₂PPh₂}₂][R = Me, (1a); or Et, (1b)] can be obtained by treating [Ag₂{µ-[CH(CO₂R)]₂PPh₂}₂](R = Me or Et) with [AuCl(tht)](tht = tetrahydrothiophene)(1 : 2). Complexes (1a) and (1b) react with Cl₂Iph or I₂(1 : 1) to give gold(II) complexes [(AuX)₂{µ-[CH(CO₂R)]₂PPh₂}₂][X = Cl, R = Me (2a) or Et (2b); X = I, R = Me (3a) or Et (3b)]. If an excess of Cl₂ or I₂(1 : 2) is used gold(III) complexes [(AuX₂)₂{µ-[CH(CO₂Me)]₂PPh₂}₂][X = Cl, (4) or I, (5)] can be obtained. The corresponding derivatives with R = Et could not be prepared under the same conditions because a mixture containing mainly the gold(II) complexes (2b) and (3b) is obtained Reaction of (4) with AgClO₄(1 : 2) in acetonitrile and, after removal of AgCl and addition of L (1 : 2) gives the first reported cationic gold(II) complexes [(AuL)₂{µ-[CH(CO₂Me)]₂PPh₂}₂][ClO₄]₂[L = pyridine. (6); 3-bromopyridine, (7); 4-cyanopyridine, (8); 2,4-dimethylpyridine, (9); PPh₃, (10); or AsPh₃, (11)]. The phosphonium salts [PPh₂(CH₂CO₂R)₂]ClO₄, react with [Au(acac)L](acac = acetylacetonate)(1 : 4) to give [(AuL)₂{µ-C(CO₂R)PPh₂CH(AuL)(CO₂R)}]ClO₄[L = PPh₃, R = Me (12a) or Et (12b); L = PMe₂Ph, R = Me (13); L = P(C₆H₄OMe-4)₃, R = Et (14)].