Yuji Kajita

Publications of Yuji Kajita

• Synthesis, characterization, and reactivity of a novel μ-η2:η2-diselenidodicopper(II) complex.

  Authors: Jun Matsumoto, Yuji Kajita, Hideki Masuda

  Inorganic chemistry. 02/2012; 51(3):1236-8.

  The first μ-η(2):η(2)-diselenidodicopper(II) complex has been obtained in the reaction of a copper(I) complex with N,N',N″-tribenzyl-cis,cis-1,3,5-triaminocyclohexane and elemental selenium. TheThe first μ-η(2):η(2)-diselenidodicopper(II) complex has been obtained in the reaction of a copper(I) complex with N,N',N″-tribenzyl-cis,cis-1,3,5-triaminocyclohexane and elemental selenium. The structure and reactivity of the complex is described.

• Synthesis and characterization of cobalt(ii) complexes with tripodal polypyridine ligand bearing pivalamide groups. Selective formation of six- and seven-coordinate cobalt(ii) complexes.

  Authors: Jun Matsumoto, Tatsuya Suzuki, Yuji Kajita, Hideki Masuda

  Dalton transactions (Cambridge, England : 2003). 02/2012;

  The reactions of CoX(2) (X = Cl(-), Br(-), I(-) and ClO(4)(-)) with the tripodal polypyridine N(4)O(2)-type ligand bearing pivalamide groups, bis(6-(pivalamide-2-pyridyl)methyl)(2-pyridylmethyl)amineThe reactions of CoX(2) (X = Cl(-), Br(-), I(-) and ClO(4)(-)) with the tripodal polypyridine N(4)O(2)-type ligand bearing pivalamide groups, bis(6-(pivalamide-2-pyridyl)methyl)(2-pyridylmethyl)amine ligand (H(2)BPPA), afforded two types of Co(ii) complexes as follows. One type is purple-coloured Co(ii) complexes, [CoCl(2)(H(2)BPPA)] (1(Cl)) and [CoBr(2)(H(2)BPPA)] (1(Br)) which were prepared when X = Cl(-) and Br(-), respectively. The other type is pale pink-coloured Co(ii) complexes, [Co(MeOH)(H(2)BPPA)](ClO(4)(-))(2) (2·(ClO(4)(-))(2)) and [Co(MeCN)(H(2)BPPA)](I(-))(2) (2·(I(-))(2)), which were obtained when X = I(-) and ClO(4)(-), respectively. From the reaction of 1(Cl) and NaN(3), a purple-coloured complex, [Co(N(3))(2)(H(2)BPPA)] (1(azide)), was obtained. These Co(ii) complexes were characterized by X-ray structural analysis, IR and reflectance spectroscopies, and magnetic susceptibility measurements. All these Co(ii) complexes were shown to be in a d(7) high-spin state based on magnetic susceptibility measurements. The former Co(ii) complexes revealed a six-coordinate octahedron with one amine nitrogen, three pyridyl nitrogens, and two counter anions, and one coordinated anion, Cl(-), Br(-) and N(3)(-), forming intramolecular hydrogen bonds with two pivalamide N-H groups. On the other hand, the latter Co(ii) complexes showed a seven-coordinate face-capped octahedron with one amine nitrogen, three pyridyl nitrogens, two pivalamide carbonyl oxygens and MeCN or MeOH. In these structures, intramolecular hydrogen bonding interaction was not observed, and the metal ion was coordinated by the pivalamide carbonyl oxygens and solvent molecule instead of the counter anions. The difference in coordination geometries might be attributable to the coordination ability and ionic radii of the counteranions; smaller strongly binding anions such as Cl(-), Br(-) and N(3)(-) gave the former complexes, whereas bulky weakly binding anions such as I(-) and ClO(4)(-) afforded the latter ones. In order to demonstrate this hypothesis, the small stronger coordinating ligand, azide, was added to complexes 2·(ClO(4)(-))(2) to obtain the dinuclear cobalt(ii) complex in which two six-coordinate octahedral cobalt(ii) species were bridged with azide, 3·(ClO(4)(-)). Also, the abstraction reaction of halogen anions from complexes 1(Cl) by AgSbF(6) gave a pale pink Co(ii) complex assignable to 2·(SbF(6)(-))(2).

• Erratum: Tetra-chlorido[(diphenyl-phosphino)diphenyl-phosphine oxide-κO]zirconium(IV) benzene monosolvate. Corrigendum.

  Authors: Takahiko Ogawa, Yuji Kajita, Hideki Masuda

  Acta crystallographica. Section E, Structure reports online. 01/2010; 66(Pt 2):e16.

  The chemical name of the title compound in the paper by Ogawa, Kajita & Masuda [Acta Cryst. (2009), E65, m1129] is corrected.[This corrects the article DOI: 10.1107/S1600536809031882.].

• Synthesis and Characterization of a Benzene-Dimolybdenum Complex with a New Bridging Mode.

  Authors: Yuji Kajita, Takahiko Ogawa, Jun Matsumoto, Hideki Masuda

  Inorganic chemistry. 09/2009;

  A novel dimolybdenum complex, [Mo(2)(((i)Pr)L')(2)(C(6)H(6))] (1(C(6)H(6))), has been synthesized and characterized as a benzene-ring-bridged dimolybdenum complex with aA novel dimolybdenum complex, [Mo(2)(((i)Pr)L')(2)(C(6)H(6))] (1(C(6)H(6))), has been synthesized and characterized as a benzene-ring-bridged dimolybdenum complex with a cis-mu-eta(2)(1,2):eta(2)(4,5) binding mode. Complex 1(C(6)H(6)) reacts with MeMgBr to form 2, where mu-benzene is methylated to form mu-xylene.

• Formation of a bridged butterfly-type mu-eta2:eta2-peroxo dicopper core structure with a carboxylate group.

  Authors: Yasuhiro Funahashi, Tomohide Nishikawa, Yuko Wasada-Tsutsui, Yuji Kajita, Syuhei Yamaguchi, Hidekazu Arii, Tomohiro Ozawa, Koichiro Jitsukawa, Takehiko Tosha, Shun Hirota, Teizo Kitagawa, Hideki Masuda

  Journal of the American Chemical Society. 01/2009; 130(49):16444-5.

• {μ-Bis(1-methyl-imidazol-2-yl)methane-κN:N}bis-{[(1-methyl-imidazol-2-yl)methane-κN,N]copper(I)} bis-(tri-fluoro-methane-sulfonate).

  Authors: Jun Matsumoto, Yuji Kajita, Hideki Masuda

  Acta crystallographica. Section E, Structure reports online. 01/2009; 65(Pt 11):m1286-7.

  The title compound, [Cu(2)(C(9)H(12)N(4))(3)](CF(3)SO(3))(2), contains two Cu(I) ions, three bis-(1-methyl-imidazol-2-yl)methane (Me(2)BIM) ligands, and two trifluoromethanesulfonate anions in theThe title compound, [Cu(2)(C(9)H(12)N(4))(3)](CF(3)SO(3))(2), contains two Cu(I) ions, three bis-(1-methyl-imidazol-2-yl)methane (Me(2)BIM) ligands, and two trifluoromethanesulfonate anions in the asymmetric unit. Each Cu(I) ion has a distorted trigonal-planar geometry and is coordinated by two N atoms from the Me(2)BIM ligand and another N atom from the Me(2)BIM that acts as a bridging ligand, another N atom of the bridging Me(2)BIM being linked to the second Cu(I) ion. The imidazole rings of Me(2)BIM form intra-molecular π-π stacking inter-actions [centroid-centroid distances = 3.445 (2) and 3.547 (2) Å].

• Tetra-chlorido[(diphenyl-phosphino)diphenyl-phosphine oxide-κO]zirconium(IV) benzene monosolvate.

  Authors: Takahiko Ogawa, Yuji Kajita, Hideki Masuda

  Acta crystallographica. Section E, Structure reports online. 01/2009; 65(Pt 9):m1129.

  In the title centrosymmetric mononuclear Zr(IV) compound, [ZrCl(4){P(O)(C(6)H(5))(2)P(C(6)H(5))(2)}(2)]·C(6)H(6), the central Zr(IV) ion is coordinated by two O atoms from two symmetry-relatedIn the title centrosymmetric mononuclear Zr(IV) compound, [ZrCl(4){P(O)(C(6)H(5))(2)P(C(6)H(5))(2)}(2)]·C(6)H(6), the central Zr(IV) ion is coordinated by two O atoms from two symmetry-related (diphenyl-phosphino)diphenyl-phosphine ligands and four Cl atoms in a distorted octahedral geometry with the four Cl atoms in the equatorial positions. The mol-ecule lies about a center of inversion and the benzene solvent mol-ecule about another center of inversion. The P=O bond [1.528 (2) Å] is slightly longer than a typical P=O double bond (average 1.500 ).

• Formation of a Bridged Butterfly-Type mu-eta(2):eta(2)-Peroxo Dicopper Core Structure with a Carboxylate Group.

  Authors: Yasuhiro Funahashi, Tomohide Nishikawa, Yuko Wasada-Tsutsui, Yuji Kajita, Syuhei Yamaguchi, Hidekazu Arii, Tomohiro Ozawa, Koichiro Jitsukawa, Takehiko Tosha, Shun Hirota, Teizo Kitagawa, Hideki Masuda

  Journal of the American Chemical Society. 12/2008;

• Syntheses, Characterization, and Reactivities of (μ-η2:η2-Disulfido)dicopper(II) Complexes with N-Alkylated cis,cis-1,3,5-Triaminocyclohexane Derivatives

  Authors: Yuji Kajita, Jun Matsumoto, Isao Takahashi, Shun Hirota, Yasuhiro Funahashi, Tomohiro Ozawa, Hideki Masuda

  European Journal of Inorganic Chemistry. 01/2008; 2008(25):3977-3986.

  Three novel (disulfido)dicopper(II) complexes with N-alkylated cis,cis-1,3,5-triaminocyclohexane derivatives, [Cu2(S2)(R3TACH)]X2 [(R, X) = (Et, CF3SO3) (1), (iBu, SbF6) (2), and (Bn, SbF6) (3)],Three novel (disulfido)dicopper(II) complexes with N-alkylated cis,cis-1,3,5-triaminocyclohexane derivatives, [Cu2(S2)(R3TACH)]X2 [(R, X) = (Et, CF3SO3) (1), (iBu, SbF6) (2), and (Bn, SbF6) (3)], have been synthesized and characterized by elemental, electrochemical, and X-ray structure analyses, and electronic absorption, IR, ESI mass, and resonance Raman spectroscopic methods. The X-ray crystal structures indicate that the two sulfur and two copper atoms of these complexes form a Cu2(S2) structure with slight bending of the two planes defined by the CuS2 plane at angles of 166.12° (the individual bending angles are 175.56° for 1a and 156.67° for 1b), 154.74°, and 180° for 1, 2, and 3, respectively. The UV/Vis absorption spectra of 1, 2, and 3 have a sharp band at ca. 360 nm with a broadened shoulder at 400–480 nm and low intensity d–d bands in the range 666–671 nm. The resonance Raman spectra of the complexes have peaks assignable to a ν(S–S) band at 483–484 cm–1. The complexes have reduction waves at –974 to –946 vs. [Fe(C5H5)2]/[Fe(C5H5)2]+ for 1, –993 to –976 for 2, and –948 to –928 mV for 3. These values are in a low-potential region relative to bis(μ-OH)dicopper complexes with R3TACH. This may be explained by the occurrence of strong π-donation from the disulfide ligands as observed for previously reported (disulfido)Ru complexes. Compounds 1, 2, and 3 react with PPh3 to give S=PPh3 in yields of 65 ± 3.5, 76 ± 1, and 50 ± 2 %, respectively. These results are discussed in terms of the relationship between the dihedral angles in the Cu2(S2) core and the reactivity of S22–. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

• Syntheses, characterization, and dioxygen reactivities of Cu(I) complexes with cis,cis-1,3,5-triaminocyclohexane derivatives: a Cu(III)2O2 intermediate exhibiting higher C-H activation.

  Authors: Yuji Kajita, Hidekazu Arii, Takahiro Saito, Yamato Saito, Shigenori Nagatomo, Teizo Kitagawa, Yasuhiro Funahashi, Tomohiro Ozawa, Hideki Masuda

  Inorganic chemistry. 05/2007; 46(8):3322-35.

  Six Cu(I) complexes with cis,cis-1,3,5-triaminocyclohexane derivatives (R3CY, R = Et, iBu, and Bn), [Cu(MeCN)(Et3CY)]SbF6 (1), [Cu(MeCN)(iBu3CY)]SbF6 (2), [Cu(MeCN)(Bn3CY)]SbF6 (3),Six Cu(I) complexes with cis,cis-1,3,5-triaminocyclohexane derivatives (R3CY, R = Et, iBu, and Bn), [Cu(MeCN)(Et3CY)]SbF6 (1), [Cu(MeCN)(iBu3CY)]SbF6 (2), [Cu(MeCN)(Bn3CY)]SbF6 (3), [Cu(CO)(Et3CY)]SbF6 (4), [Cu(CO)(iBu3CY)]SbF6 (5), and [Cu(CO)(Bn3CY)]SbF6 (6), were prepared to probe the ability of copper complexes to effectively catalyze oxygenation reactions. The complexes were characterized by elemental analysis, electrochemical and X-ray structure analyses, electronic absorption spectroscopy, IR spectroscopy, 1H NMR spectroscopy, and ESI mass spectrometry. The crystal structures of 1-3 and 6 and the CO stretching vibrations (nuCO) of 4-6 demonstrate that the ability of R3CY to donate electron density to the Cu(I) atom is stronger than that of the previously reported ligands, 1,4,7-triazacyclononane (R3TACN) and 1,4,7-triazacyclodecane (R3TACD). Reactions of complexes 1-3 with dioxygen in THF or CH2Cl2 at -105 to -80 degrees C yield bis(mu-oxo)dicopper(III) complexes 7-9 as intermediates as confirmed by electronic absorption spectroscopy and resonance Raman spectroscopy. The Cu-O stretching vibrations, nu(Cu-O) for 7 (16O2: 553, 581 cm-1and 18O2: 547 cm-1) and 8 (16O2: 571 cm-1 and 18O2: 544 cm-1), are observed in a lower energy region than previously reported for bis(micro-oxo) complexes. The decomposition rates of complexes 7-9 in THF at -90 degrees C are 2.78 x 10-4 for 7, 8.04 x 10-4 for 8, and 3.80 x 10-4 s-1 for 9. The decomposition rates of 7 and 8 in CH2Cl2 were 5.62 x 10-4 and 1.62 x 10-3 s-1, respectively, and the thermal stabilities of 7-9 in CH2Cl2 are lower than the values measured for the complexes in THF. The decomposition reactions obeyed first-order kinetics, and the H/D isotope experiments for 8 and 9 indicate that the N-dealkylation reaction is the rate-determining step in the decomposition processes. On the other hand, the decomposition reaction of 7 in THF results in the oxidation of THF (acting as an exogenous substrate) to give 2-hydroxy tetrahydrofuran and gamma-butyrolactone as oxidation products. Detailed investigation of the N-dealkylation reaction for 8 by kinetic experiments using N-H/D at -90 degrees C showed a kinetic isotope effect of 1.25, indicating that a weak electrostatic interaction between the N-H hydrogen and mu-oxo oxygen contributes to the major effect on the rate-determining step of N-dealkylation. X-ray crystal structures of the bis(micro-hydroxo)dicopper(II) complexes, [Cu2(OH)2(Et3CY)2](CF3SO3)2 (10), [Cu2(OH)2(iBu3CY)2](CF3SO3)2 (11), and [Cu2(OH)2(Bn3CY)2](ClO4)2 (12), which have independently been prepared as the final products of bis(micro-oxo)dicopper(III) intermediates, suggest that an effective interaction between N-H and mu-oxo in the Cu(III)2(micro-O)2 core may enhance the oxidation ability of the metal-oxo species.

• {μ-Bis(1-methyl­imidazol-2-yl)methane-κ2 N 3:N 3′}bis­{[(1-methyl­imidazol-2-yl)methane-κ2 N 3,N 3′]copper(I)} bis­(tri­fluoro­methane­sulfonate)

  Authors: Jun Matsumoto, Yuji Kajita, Hideki Masuda

  The title compound, [Cu2(C9H12N4)3](CF3SO3)2, contains two CuI ions, three bis­(1-methyl­imidazol-2-yl)methane (Me2BIM) ligands, and two trifluoromethanesulfonate anions in the asymmetric unit. EachThe title compound, [Cu2(C9H12N4)3](CF3SO3)2, contains two CuI ions, three bis­(1-methyl­imidazol-2-yl)methane (Me2BIM) ligands, and two trifluoromethanesulfonate anions in the asymmetric unit. Each CuI ion has a distorted trigonal-planar geometry and is coordinated by two N atoms from the Me2BIM ligand and another N atom from the Me2BIM that acts as a bridging ligand, another N atom of the bridging Me2BIM being linked to the second CuI ion. The imidazole rings of Me2BIM form intra­molecular π–π stacking inter­actions [centroid–centroid distances = 3.445 (2) and 3.547 (2) Å].

• Synthesis and Reactivity of $\mu$-$\eta^{2}$:$\eta^{2}$-Disulfido Dicopper(II) Complex with N , N $ '$, N $''$-Trimethyl-1,3,5- cis , cis -triaminocyclohexane

  Authors: Jun Matsumoto, Yuji Kajita, Hideki Masuda

  Japanese Journal of Applied Physics. 50(1):01AK04.