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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

Title
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
Authors
Kojima T.Nakayama K.Ikemura K.Ogura T.Fukuzumi S.
Ewha Authors
Shunichi Fukuzumi
SCOPUS Author ID
Shunichi Fukuzumiscopus
Issue Date
2011
Journal Title
Journal of the American Chemical Society
ISSN
0002-7863JCR Link
Citation
vol. 133, no. 30, pp. 11692 - 11700
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
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 H 2O 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 1H 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)(CH 3CN)], 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. © 2011 American Chemical Society.
DOI
10.1021/ja2037645
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자연과학대학 > 화학·나노과학전공 > Journal papers
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