Kiyoshi Fujisawa

Ibaraki University, Mito-shi, Ibaraki-ken, Japan

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Publications (130)321.99 Total impact

  • Yui Morishima, David James Young, Kiyoshi Fujisawa
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    ABSTRACT: Five halogen substituted pyrazolates, 4-chloro-3,5-diisopropylpyrazole (4-Cl-3,5-iPr2pzH), 4-bromo-3,5-diisopropylpyrazole (4-Br-3,5-iPr2pzH), 4-iodo-3,5-diisopropylpyrazole (4-I-3,5-iPr2pzH), 4-chloro-3,5-diphenylpyrazole (4-Cl-3,5-Ph2pzH), and 4-bromo-3,5-diphenylpyrazole (4-Br-3,5-Ph2pzH) were conveniently prepared by halogenation of the appropriate pyrazoles with N-halosuccinimides (NXS) (X = Cl, Br, and I) followed by complexation of the pyrazolate anions with silver(I) nitrate. Single crystal X-ray analysis revealed either dimeric trinuclear {[Ag(μ-4-X-3,5-R2pz)]3}2 (R = iPr, X = Cl, Br, and I) or trinuclear [Ag(μ-4-X 3,5-R2pz)]3 (R = iPr, X = I; R = Ph, X = Cl, R = Ph, X = Br) structures, the latter held together with argentophilic interactions (Ag•••Ag interactions) that could also be observed in the Raman spectra. The electronegativity of the halogen substituent could be correlated with the strength of the Ag•••Ag interaction and the wavelength of solid-state photoluminescence. All complexes were emissive on UV irradiation at low temperatures, with the colour of emission from the diisopropyl substituted analogues red shifted by the halogens in the order Cl (red) > Br (orange) > I (yellow). Emission from the diphenyl substituted analogues was dominated by the extended aromatic system and was largely invariant to the halogens.
    Dalton Transactions 08/2014; · 4.10 Impact Factor
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    ABSTRACT: The α-ketocarboxylatocopper(II) complex [{Cu(L1)}{O2CC(O)CH(CH3)2}] can be spontaneously converted into the binuclear oxalatocopper(II) complex [{Cu(L1)}2(μ-C2O4)] upon exposure to O2/CO2 gas. (13)C-labeling experiments revealed that oxalate ions partially incorporated (13)CO2 molecules. Furthermore, the bicarbonatocopper(I) complex (NEt4)[Cu(L1){O2C(OH)}] in an Ar atmosphere and the α-ketocarboxylatocopper(I) complex Na[Cu(L1){O2CC(O)CH(CH3)2}] in an O2 atmosphere were also transformed spontaneously into the oxalato complex [{Cu(L1)}2(μ-C2O4)].
    Inorganic chemistry. 08/2014;
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    ABSTRACT: The hydroxylation of aromatic substrates catalyzed by coupled binuclear copper enzymes has been observed with side-on-peroxo-dicopper(II) (P) and bis-μ-oxo-dicopper(III) (O) model complexes. The substrate-bound-O intermediate in [Cu(II)2(DBED)2(O)2](2+) (DBED=N,N'-di-tert-butyl-ethylenediamine) was shown to perform aromatic hydroxylation. For the [Cu(II)2(NO2-XYL)(O2)](2+) complex, only a P species was spectroscopically observed. However, it was not clear whether this O-O bond cleaves to proceed through an O-type structure along the reaction coordinate for hydroxylation of the aromatic xylyl linker. Accurate evaluation of these reaction coordinates requires reasonable quantitative descriptions of the electronic structures of the P and O species. We have performed Cu L-edge XAS on two well-characterized P and O species to experimentally quantify the Cu 3d character in their ground state wavefunctions. The lower per-hole Cu character (40±6%) corresponding to higher covalency in the O species compared to the P species (52±4%) reflects a stronger bonding interaction of the bis-μ-oxo core with the Cu(III) centers. DFT calculations show that 10-20% Hartree-Fock (HF) mixing for P and ~38% for O species are required to reproduce the Cu-O bonding; for the P species this HF mixing is also required for an antiferromagnetically coupled description of the two Cu(II) centers. B3LYP (with 20% HF) was, therefore, used to calculate the hydroxylation reaction coordinate of P in [Cu(II)2(NO2-XYL)(O2)](2+). These experimentally calibrated calculations indicate that the electrophilic attack on the aromatic ring does not involve formation of a Cu(III)2(O(2-))2 species. Rather, there is direct electron donation from the aromatic ring into the peroxo σ(*) orbital of the Cu(II)2(O2(2-)) species, leading to concerted C-O bond formation with O-O bond cleavage. Thus, species P is capable of direct hydroxylation of aromatic substrates without the intermediacy of an O-type species.
    Journal of the American Chemical Society 10/2013; · 10.68 Impact Factor
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    ABSTRACT: In the title compound, [Cu(C18H32BN4)(C18H15P)], the Cu(I) ion is coordinated by two N atoms from the anionic bidentate chelating bis(3,5-diisopropylpyrazol-1-yl)dihydroborate ligand [average Cu-N distance = 1.994 (3) Å] and the P atom from a triphenylphosphane ligand [Cu-P distance = 2.1676 (8) Å] in a trigonal geometry [the sum of the angles around the Cu(I) atom is 359.6 (1)°]. The N-Cu-N angle between adjacent coordinated pyrazole-ring N atoms is 98.99 (9)°, while the average N-Cu-P angle between the coordinated pyrazole N atom and the triphenylphosphane P atom is 130.3 (1)°.
    Acta Crystallographica Section C Crystal Structure Communications 09/2013; 69(Pt 9):943-6. · 0.78 Impact Factor
  • Kiyoshi Fujisawa, Hideyuki Takisawa
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    ABSTRACT: In the thallium(I) complex, [Tl(C48H70BN6)], of tris[3-(adamantan-1-yl)-5-isopropylpyrazol-1-yl]hydroborate, the most hindered scorpionate ligand, the Tl(I) ion is coordinated by three N atoms from the anionic tridentate chelating ligand [average Tl-N bond length = 2.522 (4) Å] in a distorted trigonal-pyramidal environment [average N-Tl-N angle around the Tl(I) ion = 76.4 (1)°]. This coordination geometry is compared with that of the reported Tl(I) complex of the super-hindered tris(7-tert-butylindazol-2-yl)hydroborate ligand.
    Acta Crystallographica Section C Crystal Structure Communications 09/2013; 69(Pt 9):986-9. · 0.78 Impact Factor
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    ABSTRACT: Needles of [{Cd[S2CN(iPr)CH2CH2OH]2}3·MeCN]∞ (2) were harvested from a dry acetonitrile solution of Cd[S2CN(iPr)CH2CH2OH]2 after one or two days and proved to be a coordination polymer in which all dithiocarbamate ligands are μ2,κ2-tridentate, bridging two cadmium atoms and simultaneously chelating one of these. If the same solution was allowed to stand for at least several days, 2 is replaced by blocks comprising a supramolecular isomer of 2, dimeric 1, with formula {Cd[S2CN(iPr)CH2CH2OH]2}2·2H2O·2MeCN, and two ligands coordinating μ2,κ2 as in 2 and the other two purely κ2-chelating. The time dependency correlates with the pivotal role of water in driving the conversion of “chain” 2 to “ball” 1; crystals of 2 could not be isolated from “wet” acetonitrile. When each of 1 and 2 are dissolved in solution, they exhibit comparable spectroscopic attributes (1H, 13C, and 113Cd NMR and UV/vis), indicating the solution structures are the same. Both 1 and 2 are luminescent in the solid state with 1 being significantly brighter than 2. Greenockite CdS nanoparticles are generated by the thermal decomposition of both 1 and 2.
    Crystal Growth & Design 06/2013; 13(7):3046–3056. · 4.69 Impact Factor
  • Kiyoshi Fujisawa, Masaaki Nabika
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    ABSTRACT: Many transition metal catalysts including both early and late transition metal ions have been investigated for olefin polymerization and copolymerization reactions. Less attention has been paid to group 7 metal catalysts. Yet, manganese(II)-based catalysts are expected to have features distinct from early and late transition metal catalysts. In this context, the present review summarizes our recent results and strategy about ethylene polymerization and ethylene copolymerization with 1-hexene with manganese(II)-based catalysts.
    Coordination Chemistry Reviews 01/2013; 257(1):119–129. · 11.02 Impact Factor
  • Source
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    ABSTRACT: Polynuclear homoleptic pyrazolate-bridged group 11 metal(I) complexes with three different alkyl substituted pyrazolate anions, 3,5-diisopropylpyrazolate (3,5-iPr2pz− = L1−), 3-tert-butyl-5-isopropylpyrazolate (3-tBu-5-iPrpz− = L3−), and 3,5-di-tert-butylpyrazolate (3,5-tBu2pz− = L4−), i.e. [Cu(μ-3,5-iPr2pz)]3 (CuL1), [Ag(μ-3,5-iPr2pz)]3 (AgL1), [Au(μ-3,5-iPr2pz)]3 (AuL1), [Cu(μ-3-tBu-5-iPrpz)]4 (CuL3), [Ag(μ-3-tBu-5-iPrpz)]3 (AgL3), [Au(μ-3-tBu-5-iPrpz)]4 (AuL3), [Cu(μ-3,5-tBu2pz)]4 (CuL4), [Ag(μ-3,5-tBu2pz)]4 (AgL4), and [Cu(μ-3,5-tBu2pz)]4 (AuL4), were systematically synthesized in order to investigate the influence of pyrazole bulkiness on their structures and physicochemical properties. The structural characterization indicates that the geometries are greatly influenced by the steric hindrance exerted by the substituent groups of the pyrazolyl rings and the differences of the central metal (I) ionic radius (Cu+ < Au+ < Ag+). These complexes were also characterized by spectroscopic techniques, namely, UV–Vis, IR/far-IR, Raman, and luminescence spectroscopy.
    Inorganica Chimica Acta 10/2010; 363(12):2977–2989. · 1.69 Impact Factor
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    ABSTRACT: Manganese(II) complex catalysts with hydrotris(pyrazolyl)borate ligands have been examined on their catalytic performance in ethylene polymerization and ethylene/1-hexene copolymerization. The activities of [Mn(L6)(Cl)(NCMe)] (1) and [Mn(L10)(Cl)] (2) activated by Al(i-Bu)3/[Ph3C][B(C6F5)4] for ethylene polymerization go up to 326 and 11 kg mol (cat−1) h−1, respectively, (L6− = hydrotris(3-phenyl-5-methyl-1-pyrazolyl)borate anion, L10− = hydrotris(3-adamantyl-5-isopropyl-1-pyrazolyl)borate anion). In particular, for ethylene/1-hexene copolymerization, complex 1 gives high-molecular-weight poly(ethylene-co-1-hexene)s with the highest Mw of 439,000 in manganese olefin polymerization catalyst systems. Moreover, the 1-hexene incorporation by complex 1 seems more efficient than that by [Mn(L3)(Cl)] (4) (L3− = hydrotris(3-tertiary butyl-5-isopropyl-1-pyrazolyl)borate anion). In this work, we demonstrated that the coordination geometry and coordination number are also important factors for ethylene polymerization reaction as well as steric hindrances and ligand frameworks in our manganese(II) catalysts. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5720–5727, 2009
    Journal of Polymer Science Part A Polymer Chemistry 09/2009; 47(21):5720 - 5727. · 3.54 Impact Factor
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    ABSTRACT: Copper coordination complexes of the neutral tetradentate nitrogen-containing ligands tris(3,5-dimethylpyrazol-1-ylmethyl)amine (L0N4) and tris(3,5-diisopropylpyrazol-1-ylmethyl)amine (L1N4), namely the copper(II) chlorido complexes [CuII(L0N4)Cl2] (1) and [CuII(L1N4)Cl2] (2), the copper(II) nitrato complexes [CuII(L0N4)(NO3)](NO3) (3) and [CuII(L1N4)(NO3)](NO3) (4), and the copper(II) sulfato complexes [CuII(L0N4)(SO4)] (5) and [CuII(L1N4)(SO4)] (6), and the copper(I) complexes [CuI(L0N4)](PF6) (7) and [CuI(L0N4)(PPh3)](ClO4) (8), have been systematically synthesized in order to investigate the influence of the number of nitrogen donors on their structures, properties, and reactivity. All copper(II) complexes were fully characterized by X-ray crystallography and by IR/far-IR, UV/Vis absorption, and ESR spectroscopy. Although the structure of 7 was not determined by X-ray crystallography, this complex and the structurally characterized copper(I) triphenylphosphane complex 8 were fully characterized by IR/far-IR and NMR spectroscopy. A comparison of the copper(II) complexes with two tris(pyrazol-1-ylmethyl)amine ligands with different bulkiness of the pyrazolyl rings has allowed us to evaluate the second coordination sphere effects of the ligands. Moreover, the structures and physicochemical properties of these complexes are compared with those of related complexes containing the neutral tridentate tris(pyrazolyl)methane ligand and the neutral bidentate bis(pyrazolyl)methane ligand. Finally, the relative stability of the copper(I) complexes is discussed. The influence of the number of nitrogen donors in copper complexes is observed from these systematic results.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
    Berichte der deutschen chemischen Gesellschaft 07/2009; 2009(26):3921 - 3934. · 2.94 Impact Factor
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    ABSTRACT: Copper(I) coordination complexes of the anionic fluorinated ligand, hydrotris(3-trifluoromethyl-5-methyl-1-pyrazolyl)borate (L0f−), i.e. the copper(I) carbonyl complex, [CuI(L0f)(CO)] (1), the copper(I) triphenylphosphine complex, [CuI(L0f)(PPh3)] (2), the copper(I) acetonitrile complex, [CuI(L0f)(NCMe)] (3), and the corresponding copper(I) triphenylphosphine complex with hydrotris(3,5-diisopropyl-1-pyrazolyl)-borate anion (L1−), i.e. [CuI(L1)(PPh3)] (4), were synthesized in order to investigate the influence of the electron-withdrawing groups on the pyrazolyl rings. The structures of complexes 1, 2, and 4 were determined by X-ray crystallography. While X-ray crystallography did not show definitive trends in terms of copper(I) atom geometry, the clear influence of the electronic structure of the pyrazolyl rings is observed by spectroscopic techniques, namely, IR and multinuclear NMR spectroscopy. Finally, the relative stability of the copper(I) complexes is discussed.
    Polyhedron 06/2009; 28(8):1447–1454. · 2.05 Impact Factor
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    ABSTRACT: The novel copper(II) hydrazido(2−) complex ligated by hydrotris(pyrazolyl)borate was synthesized to obtain insight into the copper coordination chemistry in the presence of diazene and hydrazine ligands. The structure of [{Cu(L1)}2(μ-NCOOEt)2] was determined by X-ray crystallography, where L1 = hydrotris(3,5-diisopropyl-1-pyrazolyl)borate anion, and along with spectroscopic characterization, e.g. UV–Vis and ESR, prove the presence of copper(II) centers.
    Inorganic Chemistry Communications 03/2009; 12(3):246–248. · 2.02 Impact Factor
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    ABSTRACT: Cu K-, Cu L-, and S K-edge X-ray absorption spectroscopic (XAS) data have been combined with density functional theory (DFT) calculations on [{l_brace}(TMPA)Cu{r_brace}S](ClO) (1), [{l_brace}Cu[HB(3,5-Pr{sup i}pz)]{r_brace}(S)] (2), and [{l_brace}(TMEDA)Cu{r_brace}(S)](OTf) (3) to obtain a quantitative description of their ground state wavefunctions. The Cu L-edge intensities give 63 and 37% Cu d-character in the ground state of 1 and 2, respectively, whereas the S K-pre-edge intensities reflect 20 and 48% S character in their ground states, respetively. These data indicate a more than 2-fold increase in the total disulfide bonding character in 2 relative to 1. The increase in the number of Cu?S bonds in 2 (-²:² S² bridge) compared to 1 (-¹:¹ S² bridge) dominantly determines the large increase in covalency and Cu-disulfide bond strength in 2. Cu K- and L- and S K-pre-edge energy positions directly demonstrate the Cu{sup II}/(S) nature of 3. The two disulfide(·1?)'s in 3 undergo strong bonding interactions that destabilize the resultant filled antibonding * orbitals of the (S) fragment relative to the Cu 3d levels. This leads to an inverted bonding scheme in 3 with dominantly ligand-based holes in its ground state, consistent with its description as a dicopper(II)-bis-disulfide(·1?) complex.
    Journal of the American Chemical Society 01/2009; 130(2). · 10.68 Impact Factor
  • Akinobu Shiga, Kiyoshi Fujisawa
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    ABSTRACT: The influence of the hydrotris(pyrazolyl)borate (tpzb) ligand substituents on the electron delocalization of the copper(I) center with carbon monoxide and triphenylphosphine, i.e. the copper(I) carbonyl complexes, [Cu{HB(3,5-iPr2pz)3}(CO)] (1), [Cu{HB(3,5-Me2pz)3}(CO)] (2), [Cu{HB(pz)3}(CO)] (3), [Cu{HB(3-CF3-5-Mepz)3}(CO)] (4), and the copper(I) triphenylphosphine complexes [Cu{HB(3,5-iPr2pz)3}(PPh3)] (5), [Cu{HB(3-CF3-5-Mepz)3}(PPh3)] (6), are studied by using paired interacting orbitals (PIO) analysis. Carbon monoxide is a weak σ-donor and strong π-acceptor ligand. The Cu(I)–CO interaction is entirely dominated by π back bonding between the two degenerate π∗ orbitals of carbon monoxide and two t2 type d orbitals of copper(I) ion. This interaction is clearly expressed by two PIOs, PIO-2 and PIO-3, and the strength of this π-acceptability is estimated by the summation of their overlap populations (ΣOP). On the other hand, triphenylphosphine is a strong σ-donor ligand. The Cu(I)–P interaction is dominated by donation from the P atom to the copper(I) ion and expressed by PIO-1, and the strength of this donative interaction (σ-donationability) is estimated by the overlap population of PIO-1. These results are consistent with experimental data of the CO stretching frequencies by IR spectroscopy and of 13C chemical shifts of 13CO and the broadness of the 31P signals of PPh3 by 13C and 31P NMR spectroscopy.
    Journal of Molecular Structure-theochem - J MOL STRUC-THEOCHEM. 01/2009; 913(1):173-178.
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    ABSTRACT: Copper(II) coordination complexes of the neutral ligand, tris(3-tert-butyl-5-methyl-1-pyrazolyl)methane (L2′), i.e. the copper(II) nitrato complexes [Cu(L2′)(NO3)][Cu(NO3)4]1/2 (1) and [Cu(L2′)(NO3)](ClO4) (2) and the copper(II) chloro complex [Cu(L2′)(Cl)](ClO4) (3), and its anionic borate analogue, hydrotris(3-tert-butyl-5-methyl-1-pyrazolyl)borate (L2−), i.e. the copper(II) nitrato complex [Cu(L2)(NO3)] (4) and the copper(II) chloro complex [Cu(L2)(Cl)] (5), were synthesized in order to investigate the influence of ligand framework and charge on their structure and physicochemical properties. While X-ray crystallography did not show any definitive trends in terms of copper(II) atom geometry in four-coordinate copper(II) chloro complexes 3 and 5, different structural trends were observed in five-coordinate copper(II) nitrato complexes 1, 2, and 4. These complexes were also characterized by spectroscopic techniques, namely, UV–Vis, ESR, IR/far-IR, and X-ray absorption spectroscopy.
    Inorganica Chimica Acta - INORG CHIM ACTA. 01/2009; 362(12):4500-4509.
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    ABSTRACT: A combination of spectroscopies and DFT calculations have been used to define the electronic structures of two crystallographically defined Cu(II)-phenolate complexes. These complexes differ in the orientation of the phenolate ring which results in different bonding interactions of the phenolate donor orbitals with the Cu(II), which are reflected in the very different spectroscopic properties of the two complexes. These differences in electronic structures lead to significant differences in DFT calculated reactivities with oxygen. These calculations suggest that oxygen activation via a Cu(I) phenoxyl ligand-to-metal charge transfer complex is highly endergonic (>50 kcal/mol), hence an unlikely pathway. Rather, the two-electron oxidation of the phenolate forming a bridging Cu(II) peroxoquinone complex is more favorable (11.3 kcal/mol). The role of the oxidized metal in mediating this two-electron oxidation of the coordinated phenolate and its relevance to the biogenesis of the covalently bound topa quinone in amine oxidase are discussed.
    Journal of the American Chemical Society 11/2008; 130(48):16262-73. · 10.68 Impact Factor
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    ABSTRACT: By using the neutral bidentate nitrogen-containing ligands; bis(3,5-dimethyl-1-pyrazolyl)methane (L0″), bis(3,5-diisopropyl-1-pyrazolyl)methane (L1″), bis(3-tertiary-butyl-5-isopropyl-1-pyrazolyl)methane (L3″), and bis(3,5-ditertiary-butyl-1-pyrazolyl)methane (L4″), the copper(II) nitrato complexes [Cu(L0″)2(NO3)]NO3 (1NO3), [Cu(L0″)(NO3)2] (2), [Cu(L1″)(NO3)2] (3), [Cu(L3″)(NO3)2] (4), and [Cu(L4″)(NO3)2] (5), chloro complexes [Cu(L0″)2Cl]2(CuCl4) (6CuCl4), [Cu(L0″)2Cl]2(Cu2Cl6) (6Cu2Cl6), [Cu(L1″)Cl2] (7), and [Cu(L3″)Cl2] (8), nitrito complexes [Cu(L0″)(ONO)2] (9) and [Cu(L1″)(ONO)2] (10), and the complexes with perchlorate ions [Cu(L0″)2(CH3OH)](ClO4)2 (11ClO4) and [Cu(L1″)2(H2O)](ClO4)2 (12ClO4) were systematically synthesized and fully characterized by X-ray crystallography and by IR, far-IR, UV–Vis absorption, and ESR spectroscopy. In comparison with the obtained complexes with four bis(pyrazolyl)methanes having different bulkiness at pyrazolyl rings, the second coordination sphere effects on the ligands are discussed in detail. Moreover, the structures and physicochemical properties of these obtained complexes are compared with those of the related complexes with the neutral tridentate tris(pyrazolyl)methane ligand.
    Polyhedron 04/2008; 27(5):1432-1446. · 2.05 Impact Factor
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    ABSTRACT: Five-coordinate thiolato complexes, [L1M(SMeIm)] (M = Co and Ni) (L1 = hydrotris(3,5-diisopropyl-1-pyrazolyl)borate anion and HSMeIm = 2-mercapto-1-methylimidazole), were synthesized. These complexes were compared with the corresponding Cu(II) and Zn(II) complexes with the same ligands and were also compared with the related four-coordinate complexes [L1M(SC6F5)] (HSC6F5 = pentafluorobenzenthiol). All the complexes were characterized by X-ray crystallography and UV–Vis absorption, IR, 1H NMR, and other spectroscopic techniques. All five-coordinate thiolato complexes, [L1M(SMeIm)] (M = Co, Ni, and Cu), form a distorted square pyramidal structure with a high spin state, and only [L1Zn(SMeIm)] takes a four-coordinate structure with a distorted tetrahedral configuration. The N21–M–S bond angles of the obtained five-coordinate complexes were proportional to the corresponding d value, which comes from between the equatorial basal plane with N4S ligand donor sets and metal ion. These observations and M–S bond distances affect on UV–Vis and far-IR spectral behavior.
    Inorganica Chimica Acta 03/2008; 361(4):1134–1141. · 1.69 Impact Factor
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    ABSTRACT: Starting from copper(II) hydrotris(pyrazolyl)borate precursors and substituted hydrazines, we were able to synthesize mononuclear and binuclear copper(I)–diazene complexes for the first time. The mechanism of these reactions corresponds to a simple hydrazine oxidation by the copper(II) centers. Binuclear diazene complexes contain the central Cu(I)–NRNR–Cu(I) unit, which we have structurally and spectroscopically characterized. Interestingly, usage of a sterically demanding hydrotris(pyrazolyl)borate ligand that prevents the dimer formation, leads to decomposition of the diazene complex and the isolation of a copper(I)–hydrazine complex. The same is observed when a tris(pyrazolyl)methane ligand is applied. Finally, using 1,1-diphenylhydrazine or the corresponding monophenyl derivative, we were able to obtain mononuclear Cu(I)–diazene complexes. In this case, the phenyl substituent(s) prevent the dimerization, but also stabilize the diazene ligand. Mononuclear and binuclear Cu(I)–diazene complexes are characterized by their intense reddish to purple color, which is caused by an intense Cu-d to diazene-π∗ transition in the visible region. Resonance Raman spectra of the diazene complexes show the Cu–N and N–N stretching vibrations in the 500cm−1 and 1350–1400cm−1 energy regions, respectively, in agreement with the diazene description of the complexes. The copper(I)–diazene bond in these complexes is dominated by π backbonding.
    Inorganica Chimica Acta 03/2008; 361(4):901-915. · 1.69 Impact Factor
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    ABSTRACT: Two crystal structures of the mononuclear copper(I)-nitrosyl complexes [Cu(L3)(NO)] (1) and [Cu(L3')(NO)](ClO4) (2) with the related coligands L3- (hydrotris(3-tert-butyl-5-isopropyl-1-pyrazolyl)borate) and L3' (tris(3-tert-butyl-5-isopropyl-1-pyrazolyl)methane) are presented. These compounds are then investigated in detail using a variety of spectroscopic methods. Vibrational spectra show nu(N-O) at 1698 cm(-1) and nu(Cu-NO) split at 365/338 cm(-1) for 1, which translates to force constants of 12.53 (N-O) and 1.31 mdyn/A (Cu-NO), respectively. The weak Cu-NO force constant is in agreement with the observed instability of the Cu-NO bond. Interestingly, complex 2 with the neutral coligand L3' shows a stronger N-O bond, evident from nu(N-O) at 1742 cm(-1). This difference is attributed to a true second coordination sphere effect, where the covalency of the Cu(I)-NO bond is not altered. The EPR spectrum of 1 is in agreement with the Cu(I)-NO(radical) electronic structure of the complexes, as obtained from density functional theory (DFT) calculations. In addition, an interesting trend between g parallel(gz) and the Cu-N-O angle is established. Finally, high-quality MCD spectra of 1 are presented and assigned using TD-DFT calculations. Based on the in-depth spectroscopic characterization of end-on bound NO to copper(I) presented in this work, it is possible to determine the binding mode of the Cu-NO intermediate of Cu nitrite reductase studied by Scholes and co-workers (Usov, O. M.; Sun, Y.; Grigoryants, V. M.; Shapleigh, J. P.; Scholes, C. P., J. Am. Chem. Soc. 2006, 128, 13102-13111) in solution as strongly bent (approximately 135 degrees) but likely not side-on.
    Journal of the American Chemical Society 02/2008; 130(4):1205-13. · 10.68 Impact Factor

Publication Stats

538 Citations
321.99 Total Impact Points

Institutions

  • 2013
    • Ibaraki University
      • Department of Chemistry
      Mito-shi, Ibaraki-ken, Japan
  • 2000–2010
    • University of Tsukuba
      • Graduate School of Pure and Applied Sciences
      Tsukuba, Ibaraki, Japan
  • 2003–2008
    • Stanford University
      • Department of Chemistry
      Stanford, CA, United States
  • 2007
    • University of Michigan
      • Department of Chemistry
      Ann Arbor, MI, United States
  • 1991–2000
    • Tokyo Institute of Technology
      • Chemical Resources Laboratory
      Edo, Tōkyō, Japan