Characteristics of Mononuclear Ruthenium–Oxo Complexes Adjusted by Axial Ligand for the Catalysis of Oxygen-Transfer Reactions
作者:Takeshi Okumura、Yuji Morishima、Hiroyoshi Shiozaki、Takeyoshi Yagyu、Yasuhiro Funahashi、Tomohiro Ozawa、Koichiro Jitsukawa、Hideki Masuda
DOI:10.1246/bcsj.80.507
日期:2007.3.15
Ruthenium(II) complexes, [Ru(babp)(dmso)L], consisting of tetradentate square-planar ligand (babp = 6,6′-bis(benzoylamino)-2,2′-bipyridinato) and two monodentate axial ones, DMSO and L (L = dmso or heterocycles), were synthesized and structurally characterized using UV–vis, NMR, ESI-MS, and IR spectroscopies and X-ray crystallography. These complexes showed catalytic activity toward the oxygen-atom-transfer reactions, such as epoxidation, allylic oxidation, cleavage reaction of olefins, and sulfoxidation of thioethers, in the presence of oxidant, PhIO. The relationship between the coordination structure and the catalytic activities of [Ru(babp)(dmso)L] was investigated. The active species for the reaction was assigned to be a high valent RuV=O or RuVI=O species. The oxo ligand was generated from the ligand-exchange reaction involving the dmso attached to [Ru(babp)(dmso)L]. Some complexes having a labile ligand at an axial position gave a RuVI=O species as an active intermediate, and others having moderate coordinating one gave a RuV=O one. The oxidation activities of these complexes were affected by the axial ligand, L, through the trans-influence.
由四价方形平面配体(babp = 6,6′-双(苯甲酰氨基)-2,2′-联吡啶)和两个单价轴配体组成的钌(II)配合物[Ru(babp)(dmso)L]、合成了 DMSO 和 L(L = dmso 或杂环)配合物,并利用紫外可见光谱、核磁共振、ESI-MS 和红外光谱以及 X 射线晶体学对其进行了结构表征。在氧化剂 PhIO 的存在下,这些配合物对氧原子转移反应(如环氧化反应、烯丙基氧化反应、烯烃的裂解反应和硫醚的硫氧化反应)具有催化活性。研究了[Ru(babp)(dmso)L]的配位结构与催化活性之间的关系。反应的活性物种被认为是高价的 RuV=O 或 RuVI=O 物种。氧化配体是由[Ru(babp)(dmso)L]上附着的 dmso 发生配体交换反应生成的。一些在轴向位置有易变配体的配合物产生了 RuVI=O 物种作为活性中间体,而其他有中等配位配体的配合物则产生了 RuV=O 物种。这些配合物的氧化活性受轴向配体 L 的反式影响。