Development of systematic synthetic method for iridium dimer complexes

点击翻译按钮获取中文摘要

A bis (μ-acetato) dicarbonyldichlorodiiridium (II) complex, [Ir_2(μ-O_2CMe)_2Cl_2(CO)_2]1, was prepared by the one-step reaction of H_2IrCl_6 with MeCO_2Li under O_2 in a mixture of acetic acid and acetic anhydride. Dissolution of 1 into various ligating solvents gave [Ir_2(μ-O_2CMe)_2Cl_2(CO)_2L_2] (L=McCN : 2, dmso : 3, py : 4, 4-isopropylpyridine : 5). X-ray 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 the 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 Vvs Fc^+/Fc, respectively. Bis (μ-acetato) dichlorodicarbonyldiiridium (II) complexes with group 15 compounds as the axial ligands, [Ir_2(μ-O_2CMe)_2Cl_2(CO)_2L_2] (L=PPh_36, PCy_37, P (OPh)_38, AsPh_39, SbPh_310) were synthesized. The Ir-Ir distances were longer than those of 2-4. The complexes had a chemically reversible one- … More electron oxidation wave of which E_<1/2> values were between 0.21 of 7 and 0.75 V of 8 depending on their axial ligands. The ESR spectra of 6^<+ >, 7^<+ > and 9^<+ > at 77 K were pseudoaxially symmetric. Their hyperfine splitting indicates that their odd electron is delocalized equivalently onto the two axial phosphorous or arsenic atoms. The odd electron densities were estimated from the hyperfine coupling tensors as ρ【approximately equal】0.1 on the P atom of 6^<+ > and 7^<+ > and ρ【approximately equal】0.15 on the As atom of 9^<+ >. These ESR results indicate that their SOMO is the σ_<IrIr> orbital with σ_<IrP>^* or σ_<IrAs>^* character. DFT calculations of model complexes, [Ir_2(μ-O_2CH)_2Cl_2(CO)_2(PH_3)_2]^<+ > and [Ir_2(μ-O_2CH)_2Cl_2(CO)_2(AsH_3)_2]^<+ >, gave an electronic structure consistent with the ESR results. Similar DFT calculatiouts of [Ir_2(μ-O_2CH)_2Cl_2(CO)_2(py)_2]^<+ > gave results that its odd electron is accommodated in the orbital with σ_<IrIr>, σ^*_<IrN> and π_<IrCr>^* character. This calculated result, however, is not consistent with the previously reported results of the ESR study of [Ir_2(μ-O_2CMe)_2Cl_2(CO)_2(py)_2]^<+ >. Less