Preparation of (η-cyclo-octa-1,5-diene)halogenohydridobis(phosphine)-iridium(III) salts and kinetic study of the oxidative-addition reactions of (η-cyclo-octa-1,5-diene)bis(phosphine)iridium(I) salts with hydrohalogenic acids: evidence for anionic intermediates
The complexes [IrH(X)(cod)L2][PF6][cod = cyclo-octa-1,5-diene, X = Cl, Br, or I, L = PPh2(OMe) or PMePh2; X = Cl or Br, L = PEtPh2] and [IrHX2(cod)L](X = Br or I, L = PMePh2 or PEtPh2) have been synthesised from HX (X = Cl, Br, or I) and the salts [Ir(cod)L2][PF6][L = PPh2(OMe), PMePh2, or PEtPh2]. The equilibrium (i)[Ir(cod)L2]++ Cl– [IrCl(cod)L]+ L (i) exists due to steric crowding, and explains the presence of the second chloride in the end product. Kinetic studies on both the oxidative-addition reactions of [Ir(cod)L2]+ and [lrCl(cod)L] with HCl have revealed that the nucleophilic attack of Cl– precedes the protonation of the complexes.