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.