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

Abstract

A bis(µ-acetato)dicarbonyldichlorodiiridium(II) complex, [Ir₂(µ-O₂CMe)₂Cl₂(CO)₂] 1, was prepared by a one-step reaction of H₂IrCl₆ with MeCO₂Li under O₂ in a mixed solvent of acetic acid and acetic anhydride. Dissolution of 1 in various ligating solvents gave [Ir₂(µ-O₂CMe)₂Cl₂(CO)₂L₂] (L = MeCN 2, dmso 3, py 4 or 4-isopropylpyridine 5). Crystal structure determinations of 2, 3 and 4 gave the Ir–Ir distances of 2.569(1), 2.5980(5) and 2.5918(5) Å, 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 quasi-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 their cationic radicals, of which frozen solutions gave pseudo-axially symmetric ESR spectra. The g tensors g₁ = 2.62, g₂ = 2.49 and g₃ = 1.81 for 4⁺˙ and g_⊥ = 2.51 and g_∥ = 1.82 for 5⁺˙ suggest that their odd electron is accommodated in the δ_IrIr* orbital.