Syntheses of diiridium complexes with two bridging tetrachalcogenide ligands [{Ir(η5-C5Me5)}2(μ-E4)2] (E = Se or S) and their reactions with alkynes forming mono- or di-nuclear dichalcogenolene complexes

Abstract

Treatment of [ClCp*Ir(μ-Cl)2IrCp*Cl] 1 (Cp* = η5-C5Me5) with 2 equivalents of Li2Se4 in THF at 50 °C afforded a diiridium complex with two bridging tetraselenide ligands [Cp*Ir(μ-Se4)2IrCp*] 2. The sulfur analog [Cp*Ir(μ-S4)2IrCp*] 3 was also obtained by either the reaction of 1 with Li2S4 or treatment of a mixture of [ClCp*Ir(μ-SH)2IrCp*Cl] and S8 with NEt3. When treated with MeO2CCCCO2Me (DMAD), 2 afforded the diselenolene complexes [Cp*Ir(μ-Se4){μ-Se2C2(CO2Me)2}IrCp*] and [IrCp*{Se2C2(CO2Me)2}] as well as the DMAD adduct to the latter [IrCp*{Se2C4(CO2Me)4}]. Analogous treatment of 2 with HCCCO2Me (MAMC) resulted in formation of diiridium complexes with bridging diselenolene ligand(s) [Cp*Ir(μ-Se4){μ-Se2C2H(CO2Me)}IrCp*] and [Cp*Ir{μ-Se2C2H(CO2Me)}2IrCp*] but no complex corresponding to [IrCp*{Se2C4(CO2Me)4}]. Reactions of 3 with these alkynes were also carried out for comparison, which led to exclusive formation of the mononuclear complexes: [IrCp*{S2C2(CO2Me)2}] and [IrCp*{S2C4(CO2Me)4}] for DMAD and [IrCp*{S2C2H(CO2Me)}] for MAMC, respectively. X-Ray analyses were undertaken to clarify the detailed structures of seven complexes.