Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA.
Inorg Chem. 2010 Apr 5;49(7):3531-9. doi: 10.1021/ic100032n.
To further understand copper-promoted oxidation reactions, the Cu(I) complexes LCuX (L = N,N'-di-tert-butyl-N,N'-dimethylethylenediamine; X = benzoylformate (BF) or p-nitro-benzoylformate) were synthesized, fully characterized by X-ray crystallography and spectroscopy in solution, and their reactivity with O(2) at -80 degrees C examined. Oxidative decarboxylation of the alpha-ketocarboxylate ligand was observed, but only to a significant extent when cyclohexene, cyclooctene, or acetonitrile was present. Spectroscopic and conductivity data are consistent with mechanistic postulates involving displacement of the alpha-ketocarboxylate by the additives to a small extent, followed by oxygenation of the LCu(I) moiety to yield copper-oxygen species that subsequently induce decarboxylation. To test these hypotheses, spectroscopic and kinetic studies of the reactions of Bu(4)NBF with preformed mu-eta(2):eta(2)-peroxodicopper(II) and/or bis(mu-oxo)dicopper(III) complexes supported by L or N,N,N',N'-tetramethylpropylenediamine were performed. In an illustration of a new mode of reactivity for such dicopper-oxygen cores, decarboxylation of the added alpha-ketocarboxylate was observed and the intermediacy of a carboxylate-bridged mu-eta(2):eta(2)-peroxodicopper(II) complex was implicated.
为了进一步理解铜促进的氧化反应，合成了 Cu(I) 配合物 LCuX（L = N,N'-二-叔丁基-N,N'-二甲乙基乙二胺；X = 苯甲酰甲酸酯 (BF) 或对硝基苯甲酰甲酸酯），通过 X 射线晶体学和溶液光谱学进行了充分的表征，并在-80°C 下考察了它们与 O(2)的反应性。观察到 α-酮羧酸配体的氧化脱羧，但只有在环己烯、环辛烯或乙腈存在时才会显著发生。光谱和电导率数据与涉及添加剂在一定程度上取代α-酮羧酸配体的机制假设一致，随后是 LCu(I) 部分的氧化，生成随后诱导脱羧的铜-氧物种。为了验证这些假设，进行了 Bu(4)NBF 与预形成的 μ-η(2):η(2)-过氧二铜(II) 和/或双(μ-氧)二铜(III) 配合物的反应的光谱和动力学研究，这些配合物由 L 或 N,N,N',N'-四甲基丙二胺支持。在这种双核氧核新反应模式的说明中，观察到添加的α-酮羧酸的脱羧，并且涉及羧酸盐桥联的 μ-η(2):η(2)-过氧二铜(II) 配合物的中间体。
