A one-step synthesis of an iridium(II) dinuclear complex. Preparation, structures and properties of bis(mu-acetato)dicarbonyldichlorodiiridium(II) complexes

A bis(mu-acetato)dicarbonyldichlorodiiridium(II) complex, [Ir-2(mu-O2CMe)(2 )Cl-2(CO)(2)] 1, was prepared by a one-step reaction of H2IrCl6 with MeCO2L i under O-2 in a mixed solvent of acetic acid and acetic anhydride. Dissolu tion of 1 in various ligating solvents gave [Ir-2(mu-O2CMe)(2)Cl-2(CO)(2)L- 2] (L=MeCN 2, dmso 3, py 4 or 4-isopropylpyridine 5). Crystal structure det erminations of 2, 3 and 4 gave the Ir-Ir distances of 2.569(1), 2.5980(5) a nd 2.5918(5) Angstrom, respectively, which are in the range of reported Ir- II-Ir-II single-bond distances. CV of 2, 4 and 5 exhibited a one-electron q uasi-reversible oxidation wave at E-1/2 of 1.30, 0.97 and 0.94 V vs. Fc(+)- Fc, respectively. Complex 3 gave no CV response in the potential window of dmso. Electrolytic or radiolytic one-electron oxidation of 4 and 5 gave the ir cationic radicals, of which frozen solutions gave pseudo-axially symmetr ic ESR spectra. The g tensors g(1)=2.62, g(2)=2.49 and g(3)=1.81 for 4(+.) and g(perpendicular to)=2.51 and g(parallel to)=1.82 for 5(+.) suggest that their odd electron is accommodated in the delta(IrIr)* orbital.