Synthesis of sulfido- and thiolato-bridged Ir3 cluster and its reactions with alkyne and isocyanide including highly regioselective cyclotrimerization of methyl propiolate

Reactions of a sulfido- and thiolato-bridged diiridium complex [(Cp∗Ir)2(μ-S)(μ-SCH2CH2CN)2] (Cp∗ = η5-C5Me5) with [(Cp∗MCl)2(μ-Cl)2] (M = Ir, Rh) afforded the sulfido- and thiolato-bridged trinuclear clusters [(Cp∗M)(Cp∗Ir)2(μ3-S)(μ2-SCH2CH2CN)2(μ2-Cl)]Cl (4: M = Ir, 5: M = Rh). Upon treatment with XyNC (Xy = 2,6-Me2C6H3) in the presence of KPF6 at 60 °C, 4 was converted into a mixture of a mononuclear XyNC complex [Cp∗Ir(SCH2CH2CN)(CNXy)2][PF6] (6) and a dinuclear XyNC complex [{Cp∗Ir(CNXy)}2(μ-S)(μ-SCH2CH2CN)][PF6] (7). On the other hand, reactions of 4 and 5 with methyl propiolate in the presence of KPF6 at 60 °C resulted in the formation of a cyclic trimer of the alkyne 1,3,5-C6H3(COOMe)3 as the sole detectable organic product. The reactions proceeded catalytically with retention of the cluster cores of 4 and 5, whereby the activity of the former was much higher than that of the latter.