Di- and Trinuclear Mixed-Valence Copper Amidinate Complexes from Reduction of Iodine

Molecular examples of mixed-valence copper complexes through chemical oxidation are rare but invoked in the mechanism of substrate activation, especially oxygen, in copper-containing enzymes. To examine the cooperative chemistry between two metals in close proximity to each other we began studying the reactivity of a dinuclear Cu­(I) amidinate complex. The reaction of [(2,6-Me2C6H3N)2C­(H)]2Cu2, 1, with I2 in tetrahydrofuran (THF), CH3CN, and toluene affords three new mixed-valence copper complexes [(2,6-Me2C6H3N)2­C­(H)]2Cu2(μ2-I3)­(THF)2, 2, [(2,6-Me2C6H3N)2­C­(H)]2Cu2(μ2-I) (NCMe)2, 3, and [(2,6-Me2C6H3N)2­C­(H)]3Cu3(μ3-I)2, 4, respectively. The first two compounds were characterized by UV–vis and electron paramagnetic resonance spectroscopies, and their molecular structure was determined by X-ray crystallography. Both di- and trinuclear mixed-valence intermediates were characterized for the reaction of compound 1 to compound 4, and the molecular structure of 4 was determined by X-ray crystallography. The electronic structure of each of these complexes was also investigated using density functional theory.通过化学氧化得到的混合价态铜配合物（mixed-valence copper complexes）的分子实例较为罕见，但这类配合物常被关联至含铜酶中底物（尤其是氧气）活化的反应机制。为探究彼此紧邻的双金属之间的协同化学行为，我们启动了对双核Cu(I)脒基配合物反应活性的研究。配合物[(2,6-Me₂C₆H₃N)₂C(H)]₂Cu₂（记为1）分别与碘单质在四氢呋喃（THF）、乙腈（CH₃CN）及甲苯中反应，依次得到三种新型混合价态铜配合物：[(2,6-Me₂C₆H₃N)₂C(H)]₂Cu₂(μ₂-I₃)(THF)₂（2）、[(2,6-Me₂C₆H₃N)₂C(H)]₂Cu₂(μ₂-I)(NCMe)₂（3）与[(2,6-Me₂C₆H₃N)₂C(H)]₃Cu₃(μ₃-I)₂（4）。前两种化合物通过紫外-可见（UV–vis）光谱与电子顺磁共振（electron paramagnetic resonance）光谱完成了表征，并借助X射线晶体学（X-ray crystallography）解析了其分子结构。针对化合物1转化为化合物4的反应过程，我们表征了双核与三核混合价态中间体，并通过X射线晶体学解析了化合物4的分子结构。此外，我们还采用密度泛函理论（density functional theory）对各配合物的电子结构开展了研究。