Syntheses of diiridium complexes with two bridging tetrachalcogenide ligands [{Ir(eta(5)-C5Me5)}(2)(mu-E-4)(2)] (E = Se or S) and their reactions with alkynes forming mono- or di-nuclear dichalcogenolene complexes

Treatment of [ClCp*Ir(mu-Cl)(2)IrCp*Cl] 1 (Cp* = eta(5)-C5Me5) with 2 equiv alents of Li2Se4 in THF at 50 degrees C afforded a diiridium complex with t wo bridging tetraselenide ligands [Cp*Ir(mu-Se-4)(2)IrCp*] 2. The sulfur an alog [Cp*Ir(mu-S-4)(2)IrCp*] 3 was also obtained by either the reaction of 1 with Li2S4 or treatment of a mixture of [ClCp*Ir(mu-SH)(2)IrCp*Cl] and S- 8 with NEt3. When treated with MeO2CC=CCO2Me (DMAD), 2 afforded the diselen olene complexes [Cp*Ir(mu-Se-4){mu-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 HC=CCO2Me (MAMC) resulted in formation of diiridium complexes with bridging diselenolene ligand(s) [Cp*Ir(mu-Se-4){m u-Se2C2H(CO2Me)}IrCp*] and [Cp*Ir{mu-Se2C2H(CO2Me)}(2)IrCp*] but no complex corresponding to [IrCp*{Se2C4(CO2Me)(4)}]. Reactions of 3 with these alkyn es were also carried out for comparison, which led to exclusive formation o f the mononuclear complexes: [IrCp*{S2C2(CO2Me)(2)}] and [IrCp*{S2C4(CO2Me) (4)}] for DMAD and [IrCp*{S2C2H(CO2Me)}] for MAMC, respectively. X-Ray anal yses were undertaken to clarify the detailed structures of seven complexes.