Schuit Institute of Catalysis, Eindhoven University of Technology, P.O. Box 513, NL-5600 MB, Eindhoven, The Netherlands.
Inorg Chem. 2010 Nov 1;49(21):10081-91. doi: 10.1021/ic101402r.
The structural and coordination properties of complexes formed upon the interaction of copper(II) and chromium(II) chlorides with dialkylimidazolium chloride (RMIm(+)Cl(-)) ionic liquids and glucose are studied by a combination of density functional theory (DFT) calculations and X-ray absorption spectroscopy (XAS). In the absence of the carbohydrate substrate, isolated mononuclear four-coordinated MeCl(4)(2-) species (Me = Cu, Cr) dominate in the ionic liquid solution. The organic part of the ionic liquid does not directly interact with the metal centers. The interactions between the RMIm(+) cations and the anionic metal chloride complexes are limited to hydrogen bonding with the basic Cl(-) ligands and the overall electrostatic stabilization of the anionic metal complexes. Exchange of Cl(-) ligands by a hydroxyl group of glucose is only favorable for CrCl(4)(2-). For Cu(2+) complexes, the formation of hydrogen bonded complexes between CuCl(4)(2-) and glucose is preferred. No preference for the coordination of metal chloride species to specific hydroxyl group of the carbohydrate is found. The formation of binuclear metal chloride complexes is also considered. The reactivity and selectivity patterns of the Lewis acid catalyzed reactions of glucose are discussed in the framework of the obtained results.
采用密度泛函理论（DFT）计算和 X 射线吸收光谱（XAS）相结合的方法，研究了铜（II）和铬（II）氯化物与二烷基咪唑鎓氯化物（RMIm(+)Cl(-)）离子液体和葡萄糖相互作用形成的配合物的结构和配位性质。在没有碳水化合物底物的情况下，孤立的单核四配位 MeCl(4)(2-)物种（Me = Cu，Cr）在离子液体溶液中占主导地位。离子液体的有机部分不会直接与金属中心相互作用。RMIm(+)阳离子与阴离子金属氯化物配合物之间的相互作用仅限于与碱性 Cl(-)配体的氢键相互作用以及阴离子金属配合物的整体静电稳定化。葡萄糖的羟基取代 Cl(-)配体仅对 CrCl(4)(2-)有利。对于 Cu(2+)配合物，CuCl(4)(2-)与葡萄糖之间形成氢键配合物是优选的。未发现金属氯化物物种与碳水化合物特定羟基配位的偏好。还考虑了双核金属氯化物配合物的形成。在所得到的结果的框架内讨论了路易斯酸催化葡萄糖反应的反应性和选择性模式。
