Formation of a Ruthenium(IV)-Oxo Complex by Electron-Transfer Oxidation of a Coordinatively Saturated Ruthenium(II) Complex and Detection of Oxygen-Rebound Intermediates in C-H Bond Oxygenation
Formation of a Ruthenium(IV)-Oxo Complex by Electron-Transfer Oxidation of a Coordinatively Saturated Ruthenium(II) Complex and Detection of Oxygen-Rebound Intermediates in C-H Bond Oxygenation
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DOI：
10.1021/ja2037645
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发表时间：
2011-08-03
影响因子：
15
通讯作者：
Fukuzumi, Shunichi
中科院分区：
文献类型：
--
作者：
Kojima, Takahiko;Nakayama, Kazuya;Fukuzumi, Shunichi
配位饱和钌（II）配合物具有四齿三（2-吡啶甲基）胺（TPA）和双齿2,2'-联吡啶（bpy）， [Ru(TPA)(bpy)](2+)(1)，在水中被Ce（IV）离子氧化生成Ru(IV)-氧配合物[Ru(O)(H(+)TPA)(bpy)](3+)(2)。用x射线晶体学测定了Ru(IV)-氧配合物2的晶体结构。在2中，TPA配体部分解离成面三叉戟，不配位的吡啶部分被质子化。丙酮-d(6)中的自旋态2在60 ~ 20 ppm范围内显示出顺磁位移的核磁共振信号，用Evans'方法用H-1核磁共振谱确定为中间自旋（S = 1）。2在室温下与各种有机底物在乙腈中反应，得到氧化和氧化产物和溶剂结合配合物[Ru(H(+)TPA)(bpy)(CH3CN)]，该配合物在醇存在下是完整的。饱和碳氢键与2的氧合反应通过两步过程进行：与2的吸氢，然后与氧反弹配合物Ru(III)-烷氧配合物解离醇产物，通过ESI-MS谱法成功检测。测定了二氢蒽（DHA）和异丙烯与2反应第一步的动力学同位素效应分别为49和12。第一步碳氢氧合的二阶速率常数与碳氢键裂解的键解离能呈线性相关。
A coordinatively saturated ruthenium(II) complex having tetradentate tris(2-pyridylmethyl)amine (TPA) and bidentate 2,2'-bipyridine (bpy), [Ru(TPA)(bpy)](2+) (1), was oxidized by a Ce(IV) ion in H2O to afford a Ru(IV)-oxo complex, [Ru(O)(H(+)TPA)(bpy)](3+) (2). The crystal structure of the Ru(IV)-oxo complex 2 was determined by X-ray crystallography. In 2, the TPA ligand partially dissociates to be in a facial tridentate fashion and the uncoordinated pyridine moiety is protonated. The spin state of 2, which showed paramagnetically shifted NMR signals in the range of 60 to 20 ppm, was determined to be an intermediate spin (S = 1) by the Evans' method with H-1 NMR spectroscopy in acetone-d(6). The reaction of 2 with various oraganic substrates in acetonitrile at room temperature afforded oxidized and oxygenated products and a solvent-bound complex, [Ru(H(+)TPA)(bpy)(CH3CN)], which is intact in the presence of alcohols. The oxygenation reaction of saturated C H bonds with 2 proceeds by two-step processes: the hydrogen abstraction with 2, followed by the dissociation of the alcohol products from the oxygen-rebound complexes, Ru(III)-alkoxo complexes, which were successfully detected by ESI-MS spectrometry. The kinetic isotope effects in the first step for the reaction of dihydroanthrathene (DHA) and cumene with 2 were determined to be 49 and 12, respectively. The second-order rate constants of C H oxygenation in the first step exhibited a linear correlation with bond dissociation energies of the C H bond cleavage.