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RISS 인기검색어
- 검색키워드
- 저자 : Shunichi Nakayama (검색결과 4 건)
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Kojima, Takahiko,Nakayama, Kazuya,Ikemura, Kenichiro,Ogura, Takashi,Fukuzumi, Shunichi American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.30
<P>A coordinatively saturated ruthenium(II) complex having tetradentate tris(2-pyridylmethyl)amine (TPA) and bidentate 2,2′-bipyridine (bpy), [Ru(TPA)(bpy)]<SUP>2+</SUP> (<B>1</B>), was oxidized by a Ce(IV) ion in H<SUB>2</SUB>O to afford a Ru(IV)-oxo complex, [Ru(O)(H<SUP>+</SUP>TPA)(bpy)]<SUP>3+</SUP> (<B>2</B>). The crystal structure of the Ru(IV)-oxo complex <B>2</B> was determined by X-ray crystallography. In <B>2</B>, the TPA ligand partially dissociates to be in a facial tridentate fashion and the uncoordinated pyridine moiety is protonated. The spin state of <B>2</B>, which showed paramagnetically shifted NMR signals in the range of 60 to −20 ppm, was determined to be an intermediate spin (<I>S</I> = 1) by the Evans’ method with <SUP>1</SUP>H NMR spectroscopy in acetone-<I>d</I><SUB>6</SUB>. The reaction of <B>2</B> with various oraganic substrates in acetonitrile at room temperature afforded oxidized and oxygenated products and a solvent-bound complex, [Ru(H<SUP>+</SUP>TPA)(bpy)(CH<SUB>3</SUB>CN)], which is intact in the presence of alcohols. The oxygenation reaction of saturated C–H bonds with <B>2</B> proceeds by two-step processes: the hydrogen abstraction with <B>2</B>, 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 <B>2</B> 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.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2011/jacsat.2011.133.issue-30/ja2037645/production/images/medium/ja-2011-037645_0013.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja2037645'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja2037645'>ACS Electronic Supporting Info</A></P>
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Kojima, Takahiko,Nakayama, Kazuya,Sakaguchi, Miyuki,Ogura, Takashi,Ohkubo, Kei,Fukuzumi, Shunichi American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.44
<P>Ruthenium(II)–acetonitrile complexes having η<SUP>3</SUP>-tris(2-pyridylmethyl)amine (TPA) with an uncoordinated pyridine ring and diimine such as 2,2′-bipyridine (bpy) and 2,2′-bipyrimidine (bpm), [Ru<SUP>II</SUP>(η<SUP>3</SUP>-TPA)(diimine)(CH<SUB>3</SUB>CN)]<SUP>2+</SUP>, reacted with <I>m</I>-chloroperbenzoic acid to afford corresponding Ru(II)–acetonitrile complexes having an uncoordinated pyridine-<I>N</I>-oxide arm, [Ru<SUP>II</SUP>(η<SUP>3</SUP>-TPA-O)(diimine)(CH<SUB>3</SUB>CN)]<SUP>2+</SUP>, with retention of the coordination environment. Photoirradiation of the acetonitrile complexes having diimine and the η<SUP>3</SUP>-TPA with the uncoordinated pyridine-<I>N</I>-oxide arm afforded a mixture of [Ru<SUP>II</SUP>(TPA)(diimine)]<SUP>2+</SUP>, intermediate-spin (<I>S</I> = 1) Ru(IV)–oxo complex with uncoordinated pyridine arm, and intermediate-spin Ru(IV)–oxo complex with uncoordinated pyridine-<I>N</I>-oxide arm. A Ru(II) complex bearing an oxygen-bound pyridine-<I>N</I>-oxide as a ligand and bpm as a diimine ligand was also obtained, and its crystal structure was determined by X-ray crystallography. Femtosecond laser flash photolysis of the isolated <I>O</I>-coordinated Ru(II)–pyridine-<I>N</I>-oxide complex has been investigated to reveal the photodynamics. The Ru(IV)–oxo complex with an uncoordinated pyridine moiety was alternatively prepared by reaction of the corresponding acetonitrile complex with 2,6-dichloropyridine-<I>N</I>-oxide (Cl<SUB>2</SUB>py-O) to identify the Ru(IV)–oxo species. The formation of Ru(IV)–oxo complexes was concluded to proceed via intermolecular oxygen atom transfer from the uncoordinated pyridine-<I>N</I>-oxide to a Ru(II) center on the basis of the results of the reaction with Cl<SUB>2</SUB>py-O and the concentration dependence of the consumption of the starting Ru(II) complexes having the uncoordinated pyridine-<I>N</I>-oxide moiety. Oxygenation reactions of organic substrates by [Ru<SUP>II</SUP>(η<SUP>3</SUP>-TPA-O)(diimine)(CH<SUB>3</SUB>CN)]<SUP>2+</SUP> were examined under irradiation (at 420 ± 5 nm) and showed selective allylic oxygenation of cyclohexene to give cyclohexen-1-ol and cyclohexen-1-one and cumene oxygenation to afford cumyl alcohol and acetophenone.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2011/jacsat.2011.133.issue-44/ja207572z/production/images/medium/ja-2011-07572z_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja207572z'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja207572z'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja207572z'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja207572z'>ACS Electronic Supporting Info</A></P>
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