Kochem Amélie, Molloy Jennifer K, Gellon Gisèle, Leconte Nicolas, Philouze Christian, Berthiol Florian, Jarjayes Olivier, Thomas Fabrice
Département de Chimie Moléculaire, UMR-5250, Université Grenoble Alpes, BP 53, 38041, Grenoble Cedex 9, France.
Chemistry. 2017 Oct 9;23(56):13929-13940. doi: 10.1002/chem.201702010. Epub 2017 Aug 11.
Three copper(II) complexes of the (R,R)-N,N'-bis(3,5-di-tert-butyl-2-aminobenzylidene)-1,2-diaminocyclohexane ligand, namely [Cu( L)], [Cu( LH)] and [Cu( LH )] , were prepared and structurally characterized. In [Cu( LH )] the copper ion lies in an octahedral geometry with the aniline groups coordinated in equatorial positions. In [Cu( L)] the anilines are deprotonated (anilido moieties) and coordinated to an almost square-planar metal ion. Complex [Cu( L)] displays two oxidation waves at E =-0.14 V and E =0.36 V vs. Fc /Fc in CH Cl . Complex [Cu( LH )] displays an irreversible oxidation wave at high potential (1.21 V), but shows a readily accessible and reversible metal-centered reduction at E =-0.67 V (Cu /Cu redox couple). Oxidation of [Cu( L)] by AgSbF produces Cu( L), which was isolated as single crystals. X-ray structure analysis discloses a contraction of the coordination sphere by 0.05 Å upon oxidation, supporting a metal-centered process. Complex Cu( L) displays an intense NIR band at 1260 nm corresponding to an anilido-to-copper(III) charge transfer transition. This compound slowly evolves in CH Cl solution towards Cu( LH), which is a copper(II) complex comprised of both anilido and aniline groups coordinated to the metal center. The copper(III) complex Cu( L) is an efficient catalyst for benzyl alcohol oxidation, with 236 TON in 24 h at 298 K, without additives other than oxygen and a base.
制备并对 (R,R)-N,N'-双(3,5-二叔丁基-2-氨基亚苄基)-1,2-二氨基环己烷配体的三种铜(II) 配合物，即 [Cu(L)]、[Cu(LH)] 和 [Cu(LH₂)] 进行了结构表征。在 [Cu(LH₂)] 中，铜离子处于八面体几何构型，苯胺基团位于赤道位置配位。在 [Cu(L)] 中，苯胺去质子化（生成苯胺基部分）并与几乎为平面正方形的金属离子配位。配合物 [Cu(L)] 在 CH₂Cl₂ 中相对于 Fc⁺/Fc 的 E = -0.14 V 和 E = 0.36 V 处显示出两个氧化波。配合物 [Cu(LH₂)] 在高电位 (1.21 V) 处显示出不可逆氧化波，但在 E = -0.67 V 处显示出易于发生且可逆的以金属为中心的还原（Cu²⁺/Cu 氧化还原对）。用 AgSbF₆ 氧化 [Cu(L)] 生成 Cu(L)，其以单晶形式分离出来。X 射线结构分析表明氧化后配位球收缩了 0.05 Å，支持以金属为中心的过程。配合物 Cu(L) 在 1260 nm 处显示出强烈的近红外带，对应于苯胺基到铜(III) 的电荷转移跃迁。该化合物在 CH₂Cl₂ 溶液中缓慢演变成 Cu(LH)，这是一种由苯胺基和苯胺基团都配位到金属中心的铜(II) 配合物。铜(III) 配合物 Cu(L) 是苯甲醇氧化的有效催化剂，在 298 K 下 24 小时内的催化转化数为 236，除了氧气和碱之外无需其他添加剂。
