Kazuyuki Tatsumi

Publications of Kazuyuki Tatsumi

• Cooperation through the Decades.

  Authors: Gerhard Erker, Yasuhiro Iwasawa, Jun Okuda, Kazuyuki Tatsumi

  Chemistry, an Asian journal. 05/2012;

• Naphthalene and Anthracene Complexes Sandwiched by Two {(Cp*)Fe(I) } Fragments: Strong Electronic Coupling between the Fe(I) Centers.

  Authors: Tsubasa Hatanaka, Yasuhiro Ohki, Takashi Kamachi, Tomonori Nakayama, Kazunari Yoshizawa, Motomi Katada, Kazuyuki Tatsumi

  Chemistry, an Asian journal. 04/2012;

  The reactions of the half-sandwich iron(II) complex [FeCl(Cp*)(tmeda)] (1; Cp*=η(5) -C(5) Me(5) , TMEDA=N,N,N',N'-tetramethylethylenediamine) with potassium naphthalenide or potassium anthracenideThe reactions of the half-sandwich iron(II) complex [FeCl(Cp*)(tmeda)] (1; Cp*=η(5) -C(5) Me(5) , TMEDA=N,N,N',N'-tetramethylethylenediamine) with potassium naphthalenide or potassium anthracenide gave the diamagnetic complexes [(Cp*)Fe(μ-polyarene)Fe(Cp*)] (polyarene=naphthalene (2), anthracene (3 a)), which have two {(Cp*)Fe} units bound to opposite faces of the polyarene. One of two {(Cp*)Fe} units in 3 a is located over the central ring of anthracene while the other is positioned over an outer ring. The {(Cp*)Fe} unit bound to the central ring of 3 a migrates to the outer ring upon heating in the solid state to give the isomer 3 b. The electrochemical potential separations between successive one-electron redox events for complexes 2 and 3 b are large. The mixed valence complexes [2](+) and [3 b](+) were synthesized by chemical oxidation. The mixed-valence complex [3 b](+) is charge delocalized on the Mössbauer timescale at 78 K, and its absorption spectrum shows an intervalence charge-transfer band. Complex [2](+) exhibits two absorption bands in the near-IR region and a slightly broadened doublet in the Mössbauer spectrum. DFT calculations were carried out to examine the electronic structures of these dinuclear iron(I) complexes to elucidate the factors responsible for their diamagnetism and to determine the degree of charge delocalization in the mixed-valence complexes.

• Non-Centrosymmetric Coordination Polymer with a Highly Hindered Octahedral Copper Center Bridged by Mandelate.

  Authors: Makoto Moriya, Shingo Tominaga, Takayoshi Hashimoto, Kazuki Tanifuji, Tsuyoshi Matsumoto, Yasuhiro Ohki, Kazuyuki Tatsumi, Junichi Kaneshiro, Yoshiaki Uesu, Wataru Sakamoto, Toshinobu Yogo

  Inorganic chemistry. 03/2012;

  A novel chiral coordination polymer, [Cu(C(6)H(5)CH(OH)COO)(μ-C(6)H(5)CH(OH)COO)] (1-L and 1-D), was synthesized through a reaction of copper acetate with l-mandelic acid at room temperature.A novel chiral coordination polymer, [Cu(C(6)H(5)CH(OH)COO)(μ-C(6)H(5)CH(OH)COO)] (1-L and 1-D), was synthesized through a reaction of copper acetate with l-mandelic acid at room temperature. Although previously reported copper mandelate prepared by hydrothermal reaction was a centrosymmetric coordination polymer because of the racemization of mandelic acid, the current coordination polymer shows noncentrosymmetry and a completely different structure from that previously reported. The X-ray crystallography for 1-L revealed that the copper center of the compound showed a highly distorted octahedral structure bridged by a chiral mandelate ligand in the unusual coordination mode to construct a one-dimensional (1D) zigzag chain structure. These 1D chains interdigitated each other to give a layered structure as a result of the formation of multiple aromatic interactions and hydrogen bonds between hydroxyl and carboxylate moieties at mandelate ligands. The coordination polymer 1-L belongs to the noncentrosymmetric space group of C2 to show piezoelectric properties and second harmonic generation (SHG) activity.

• Model Studies of Methyl CoM Reductase: Methane Formation via CH(3)-S Bond Cleavage of Ni(I) Tetraazacyclic Complexes Having Intramolecular Methyl Sulfide Pendants.

  Authors: Jun-Ichi Nishigaki, Tsuyoshi Matsumoto, Kazuyuki Tatsumi

  Inorganic chemistry. 03/2012;

  The Ni(I) tetraazacycles [Ni(dmmtc)](+) and [Ni(mtc)](+), which have methylthioethyl pendants, were synthesized as models of the reduced state of the active site of methyl coenzyme M reductase (MCR),The Ni(I) tetraazacycles [Ni(dmmtc)](+) and [Ni(mtc)](+), which have methylthioethyl pendants, were synthesized as models of the reduced state of the active site of methyl coenzyme M reductase (MCR), and their structures and redox properties were elucidated (dmmtc, 1,8-dimethyl-4,11-bis{(2-methylthio)ethyl}-1,4,8,11-tetraaza-1,4,8,11-cyclotetradecane; mtc, 1,8-{bis(2-methylthio)ethyl}-1,4,8,11-tetraaza-1,4,8,11-cyclotetradecane). The intramolecular CH(3)-S bond of the thioether pendant of [Ni(I)(dmmtc)](OTf) was cleaved in THF at 75 °C in the presence of the bulky thiol DmpSH, which acts as a proton source, and methane was formed in 31% yield and a Ni(II) thiolate complex was concomitantly obtained (Dmp = 2,6-dimesityphenyl). The CH(3)-S bond cleavage of [Ni(I)(mtc)](+) also proceeded similarly, but under milder conditions probably due to the lower potential of the [Ni(I)(mtc)](+) complex. These results indicate that the robust CH(3)-S bond can be homolytically cleaved by the Ni(I) center when they are properly arranged, which highlights the significance of the F430 Ni environment in the active site of the MCR protein.

• Coordination of methyl coenzyme m and coenzyme m at divalent and trivalent nickel cyclams: model studies of methyl coenzyme m reductase active site.

  Authors: Jun-Ichi Nishigaki, Tsuyoshi Matsumoto, Kazuyuki Tatsumi

  Inorganic chemistry. 03/2012; 51(6):3690-7.

  Divalent and trivalent nickel complexes of 1,4,8,11-tetraazacyclotetradecane, denoted as cyclam hereafter, coordinated by methyl coenzyme M (MeSCoM(-)) and coenzyme M (HSCoM(-)) have been synthesizedDivalent and trivalent nickel complexes of 1,4,8,11-tetraazacyclotetradecane, denoted as cyclam hereafter, coordinated by methyl coenzyme M (MeSCoM(-)) and coenzyme M (HSCoM(-)) have been synthesized in the course our model studies of methyl coenzyme M reductase (MCR). The divalent nickel complexes Ni(cyclam)(RSCoM)(2) (R = Me, H) have two trans-disposed RSCoM(-) ligands at the nickel(II) center as sulfonates, and thus, the nickels have an octahedral coordination. The SCoM(2-) adduct Ni(cyclam)(SCoM) was also synthesized, in which the SCoM(2-) ligand chelates the nickel via the thiolate sulfur and a sulfonate oxygen. The trivalent MeSCoM adduct [Ni(cyclam)(MeSCoM)(2)](OTf) was synthesized by treatment of [Ni(cyclam)(NCCH(3))(2)](OTf)(3) with ((n)Bu(4)N)[MeSCoM]. A similar reaction with ((n)Bu(4)N)[HSCoM] did not afford the corresponding trivalent HSCoM(-) adduct, but rather the divalent nickel complex polymer [-Ni(II)(cyclam)(CoMSSCoM)-](n) was obtained, in which the terminal thiol of HSCoM(-) was oxidized to the disulfide (CoMSSCoM)(2-) by the Ni(III) center.

• Oxido-Bridged Di-, Tri-, and Tetra-Nuclear Iron Complexes Bearing Bis(trimethylsilyl)amide and Thiolate Ligands.

  Authors: Shun Ohta, Saori Yokozawa, Yasuhiro Ohki, Kazuyuki Tatsumi

  Inorganic chemistry. 02/2012; 51(4):2645-51.

  A series of di-, tri-, and tetra-nuclear iron-oxido clusters with bis(trimethylsilyl)amide and thiolate ligands were synthesized from the reactions of Fe{N(SiMe(3))(2)}(2) (1) with 1 equiv of thiolA series of di-, tri-, and tetra-nuclear iron-oxido clusters with bis(trimethylsilyl)amide and thiolate ligands were synthesized from the reactions of Fe{N(SiMe(3))(2)}(2) (1) with 1 equiv of thiol HSR (R = C(6)H(5) (Ph), 4-(t)BuC(6)H(4), 2,6-Ph(2)C(6)H(3) (Dpp), 2,4,6-(i)Pr(3)C(6)H(2) (Tip)) and subsequent treatment with O(2). The trinuclear clusters [{(Me(3)Si)(2)N}Fe](3)(μ(3)-O){μ-S(4-RC(6)H(4))}(3) (R = H (3a), (t)Bu (3b)) were obtained from the reactions of 1 with HSPh or HS(4-(t)BuC(6)H(4)) and O(2), while we isolated a tetranuclear cluster [{(Me(3)Si)(2)N}(2)Fe(2)(μ-SDpp)](2)(μ(3)-O)(2) (4) as crystals from an analogous reaction with HSDpp. Treatment of a tertrahydrofuran (THF) solution of 1 with HSTip and O(2) resulted in the formation of a dinuclear complex [{(Me(3)Si)(2)N}(TipS)(THF)Fe](2)(μ-O) (5). The molecular structures of these complexes have been determined by X-ray crystallographic analysis.

• Synthetic analogues of [Fe4S4(Cys)3(His)] in hydrogenases and [Fe4S4(Cys)4] in HiPIP derived from all-ferric [Fe4S4{N(SiMe3)2}4].

  Authors: Yasuhiro Ohki, Kazuki Tanifuji, Norihiro Yamada, Motosuke Imada, Tomoyuki Tajima, Kazuyuki Tatsumi

  Proceedings of the National Academy of Sciences of the United States of America. 08/2011; 108(31):12635-40.

  The all-ferric [Fe(4)S(4)](4+) cluster [Fe(4)S(4){N(SiMe(3))(2)}(4)] 1 and its one-electron reduced form [1](-) serve as convenient precursors for the synthesis of 31-site differentiated [Fe(4)S(4)]The all-ferric [Fe(4)S(4)](4+) cluster [Fe(4)S(4){N(SiMe(3))(2)}(4)] 1 and its one-electron reduced form [1](-) serve as convenient precursors for the synthesis of 31-site differentiated [Fe(4)S(4)] clusters and high-potential iron-sulfur protein (HiPIP) model clusters. The reaction of 1 with four equivalents (equiv) of the bulky thiol HSDmp (Dmp = 2,6-(mesityl)(2)C(6)H(3), mesityl = 2,4,6-Me(3)C(6)H(2)) followed by treatment with tetrahydrofuran (THF) resulted in the isolation of [Fe(4)S(4)(SDmp)(3)(THF)(3)] 2. Cluster 2 contains an octahedral iron atom with three THF ligands, and its Fe(S)(3)(O)(3) coordination environment is relevant to that in the active site of substrate-bound aconitase. An analogous reaction of [1](-) with four equiv of HSDmp gave [Fe(4)S(4)(SDmp)(4)](-) 3, which models the oxidized form of HiPIP. The THF ligands in 2 can be replaced by tetramethyl-imidazole (Me(4)Im) to give [Fe(4)S(4)(SDmp)(3)(Me(4)Im)] 4 modeling the [Fe(4)S(4)(Cys)(3)(His)] cluster in hydrogenases, and its one-electron reduced form [4](-) was synthesized from the reaction of 3 with Me(4)Im. The reversible redox couple between 3 and [3](-) was observed at E(1/2) = -820 mV vs. Ag/Ag(+), and the corresponding reversible couple for 4 and [4](-) is positively shifted by +440 mV. The cyclic voltammogram of 3 also exhibited a reversible oxidation couple, which indicates generation of the all-ferric [Fe(4)S(4)](4+) cluster, [Fe(4)S(4)(SDmp)(4)].

• Cooperative catalytic activation of Si-H bonds by a polar Ru-S bond: regioselective low-temperature C-H silylation of indoles under neutral conditions by a Friedel-Crafts mechanism.

  Authors: Hendrik F T Klare, Martin Oestreich, Jun-ichi Ito, Hisao Nishiyama, Yasuhiro Ohki, Kazuyuki Tatsumi

  Journal of the American Chemical Society. 02/2011; 133(10):3312-5.

  Merging cooperative Si-H bond activation and electrophilic aromatic substitution paves the way for C-3-selective indole C-H functionalization under electronic and not conventional steric control. TheMerging cooperative Si-H bond activation and electrophilic aromatic substitution paves the way for C-3-selective indole C-H functionalization under electronic and not conventional steric control. The Si-H bond is heterolytically split by the Ru-S bond of a coordinatively unsaturated cationic ruthenium(II) complex, forming a sulfur-stabilized silicon electrophile. The Wheland intermediate of the subsequent Friedel-Crafts-type process is assumed to be deprotonated by the sulfur atom, no added base required. The overall catalysis proceeds without solvent at low temperature, only liberating dihydrogen.

• Dihydrogen activation by sulfido-bridged dinuclear Ru/Ge complexes: insight into the [NiFe] hydrogenase unready state.

  Authors: Tsuyoshi Matsumoto, Naohisa Itakura, Yukiko Nakaya, Kazuyuki Tatsumi

  Chemical communications (Cambridge, England). 11/2010; 47(3):1030-2.

  A S/SH bridged hetero-dinuclear Ru/Ge complex cation reacted with H(2) to afford the μ-S/μ-H complex. The reaction was considerably slower compared to that of the μ-S/μ-OH complex. Thus, the μ-S/μ-SHA S/SH bridged hetero-dinuclear Ru/Ge complex cation reacted with H(2) to afford the μ-S/μ-H complex. The reaction was considerably slower compared to that of the μ-S/μ-OH complex. Thus, the μ-S/μ-SH and μ-S/μ-OH complexes might provide models for the unready and ready states, respectively, of [NiFe] hydrogenase.

• Exploring the limits of frustrated Lewis pair chemistry with alkynes: detection of a system that favors 1,1-carboboration over cooperative 1,2-P/B-addition.

  Authors: Chao Chen, Florian Eweiner, Birgit Wibbeling, Roland Fröhlich, Shunsuke Senda, Yasuhiro Ohki, Kazuyuki Tatsumi, Stefan Grimme, Gerald Kehr, Gerhard Erker

  Chemistry, an Asian journal. 10/2010; 5(10):2199-208.

  The zirconocene complex [{(C₆F₅)₂B-(CH₂)₃-Cp}(Cp-PtBu₂)ZrCl₂] (6; Cp=cyclo-C₅H₄) was prepared by hydroboration of [(allyl-Cp)(Cp-PtBu₂)ZrCl₂] (5) with HB(C₆F₅)₂ ("Piers' borane"). It represents aThe zirconocene complex [{(C₆F₅)₂B-(CH₂)₃-Cp}(Cp-PtBu₂)ZrCl₂] (6; Cp=cyclo-C₅H₄) was prepared by hydroboration of [(allyl-Cp)(Cp-PtBu₂)ZrCl₂] (5) with HB(C₆F₅)₂ ("Piers' borane"). It represents a frustrated Lewis pair (FLP) in which both the Lewis acid and the Lewis base were attached at the metallocene framework. Its reaction with 1-pentyne did not result in the 1,2-addition of or deprotonation reaction by the FLP, but rather in the 1,1-carboboration of the triple bond, thereby obtaining a Z/E mixture (1.2:1) of the respective organometallic substituted alkenes 7. The analogous reaction of 1-pentyne with the phosphorous-free system [{(C₆F₅)₂B-(CH₂)₃-Cp)}CpZrCl₂] (9) gave the respective 1,1-carboboration products ((Z)-10/(E)-10≈1.3:1).

• An iron(II) carbonyl thiolato complex bearing 2-methoxy-pyridine: a structural model of the active site of [Fe] hydrogenase.

  Authors: Soichiro Tanino, Yasuhiro Ohki, Kazuyuki Tatsumi

  Chemistry, an Asian journal. 09/2010; 5(9):1962-4.

• C-H bond activation/borylation of furans and thiophenes catalyzed by a half-sandwich iron N-heterocyclic carbene complex.

  Authors: Tsubasa Hatanaka, Yasuhiro Ohki, Kazuyuki Tatsumi

  Chemistry, an Asian journal. 07/2010; 5(7):1657-66.

  A coordinatively unsaturated iron-methyl complex having an N-heterocyclic carbene ligand, [Cp*Fe(L(Me))Me] (1; Cp*=eta(5)-C(5)Me(5), L(Me)=1,3,4,5-tetramethyl-imidazol-2-ylidene), is synthesized fromA coordinatively unsaturated iron-methyl complex having an N-heterocyclic carbene ligand, [Cp*Fe(L(Me))Me] (1; Cp*=eta(5)-C(5)Me(5), L(Me)=1,3,4,5-tetramethyl-imidazol-2-ylidene), is synthesized from the reaction of [Cp*Fe(TMEDA)Cl] (TMEDA=N,N,N',N'-tetramethylethylenediamine) with methyllithium and L(Me). Complex 1 is found to activate the C-H bonds of furan, thiophene, and benzene, giving rise to aryl complexes, [Cp*Fe(L(Me))(aryl)] (aryl=2-furyl (2), 2-thienyl (3), phenyl (4)). The C-H bond cleavage reactions are applied to the dehydrogenative coupling of furans or thiophenes with pinacolborane (HBpin) in the presence of tert-butylethylene and a catalytic amount of 1 (10 mol% to HBpin). The borylation of the furan/thiophene or 2-substituted furans/thiophenes occurs exclusively at the 2- or 5-positions, respectively, whereas that of 3-substituted furans/thiophenes takes place mainly at the 5-position and gives a mixture of regioisomers. Treatment of 2 with 2 equiv of HBpin results in the quantitative formation of 2-boryl-furan and the borohydride complex [Cp*Fe(L(Me))(H(2)Bpin)] (5). Heating a solution of 5 in the presence of tert-butylethylene led to the formation of an alkyl complex [Cp*Fe(L(Me))CH(2)CH(2)tBu] (6), which was found to cleave the C-H bond of furan to produce 2. On the basis of these results, a possible catalytic cycle is proposed.

• Synthesis of coordinatively unsaturated mesityliron thiolate complexes and their reactions with elemental sulfur.

  Authors: Takayoshi Hashimoto, Yasuhiro Ohki, Kazuyuki Tatsumi

  Inorganic chemistry. 07/2010; 49(13):6102-9.

  The reactions of Fe(2)Mes(4) (1; Mes = mesityl) with bulky thiols, namely, HSDmp (Dmp = 2,6-dimesitylphenyl), HSDxp (Dxp = 2,6-dixylylphenyl), and HSBtip [Btip =The reactions of Fe(2)Mes(4) (1; Mes = mesityl) with bulky thiols, namely, HSDmp (Dmp = 2,6-dimesitylphenyl), HSDxp (Dxp = 2,6-dixylylphenyl), and HSBtip [Btip = 2,6-(2,4,6-(i)Pr(3)C(6)H(2))(2)C(6)H(3)], provided a series of iron(II) mesityl complexes bearing bulky thiolate ligands. These iron complexes are the thiolate-bridged dinuclear complexes Fe(2)Mes(2)(mu-SAr)(mu-Mes) (2a, Ar = Dmp; 2b, Ar = Dxp), the 1,2-dimethoxyethane (DME) adducts (DME)Fe(SAr)(Mes) (3a, Ar = Dmp; 3b, Ar = Dxp), the mixed-valence Fe(I)-Fe(II) dinuclear complexes (Mes)Fe(mu-SAr)(mu-S Ar) Fe (4a, Ar = Dmp; 4b, Ar = Dxp), and a low-coordinate mononuclear complex (B tipS) Fe(Mes) (5). An [Fe(8)S(7)] cluster [Fe(4)S(3)(SDmp)](2)(mu-SDmp)(2)(mu-SMes)(mu(6)-S) (6), the core structure of which is topologically relevant to that of the FeMo-cofactor of nitrogenase, was obtained from the reaction of 3a or 4a with S(8). The mu-SMes ligand in 6 is formed via insertion of a sulfur atom into the Fe-C(Mes) bond. The formation of cluster 6 from 3a or 4a demonstrates that organoiron complexes are applicable as precursors for iron-sulfur clusters.

• Dodecanuclear-ellipse and decanuclear-wheel nickel(II) thiolato clusters with efficient femtosecond nonlinear absorption.

  Authors: Chi Zhang, Tsuyoshi Matsumoto, Marek Samoc, Simon Petrie, Suci Meng, T Christopher Corkery, Robert Stranger, Jinfang Zhang, Mark G Humphrey, Kazuyuki Tatsumi

  Angewandte Chemie (International ed. in English). 06/2010; 49(25):4209-12.

• A dinuclear nickel complex modeling of the Ni(d)(II)-Ni(p)(I) state of the active site of acetyl CoA synthase.

  Authors: Tsuyoshi Matsumoto, Mikinao Ito, Mai Kotera, Kazuyuki Tatsumi

  Dalton transactions (Cambridge, England : 2003). 03/2010; 39(12):2995-7.

  The dinuclear Ni(II)-Ni(I) complex Ni(II)(dadt(Et))Ni(I)(SDmp)(PPh(3)) was synthesized as a Ni(II)(d)-Ni(I)(p) model of the A-cluster in acetyl CoA synthase. This complex was reacted withThe dinuclear Ni(II)-Ni(I) complex Ni(II)(dadt(Et))Ni(I)(SDmp)(PPh(3)) was synthesized as a Ni(II)(d)-Ni(I)(p) model of the A-cluster in acetyl CoA synthase. This complex was reacted with Co(dmgBF(2))(2)(Me)(Py) and KSDmp successively to afford Ni(dadt(Et))Ni(Me)(SDmp), which further reacts with CO to afford the acetylthioester CH(3)C(O)SDmp via reductive elimination.

• A model for the CO-inhibited form of [NiFe] hydrogenase: synthesis of CO3Fe(micro-StBu)3Ni{SC6H3-2,6-(mesityl)2} and reversible CO addition at the Ni site.

  Authors: Yasuhiro Ohki, Kazunari Yasumura, Masaru Ando, Satoko Shimokata, Kazuyuki Tatsumi

  Proceedings of the National Academy of Sciences of the United States of America. 02/2010; 107(9):3994-7.

  A [NiFe] hydrogenase model compound having a distorted trigonal-pyramidal nickel center, (CO)(3)Fe(micro-S(t)Bu)(3)Ni(SDmp), 1 (Dmp = C(6)H(3)-2,6-(mesityl)(2)), was synthesized from the reaction ofA [NiFe] hydrogenase model compound having a distorted trigonal-pyramidal nickel center, (CO)(3)Fe(micro-S(t)Bu)(3)Ni(SDmp), 1 (Dmp = C(6)H(3)-2,6-(mesityl)(2)), was synthesized from the reaction of the tetranuclear Fe-Ni-Ni-Fe complex [(CO)(3)Fe(micro-S(t)Bu)(3)Ni](2)(micro-Br)(2), 2 with NaSDmp at -40 degrees C. The nickel site of complex 1 was found to add CO or CN(t)Bu at -40 degrees C to give (CO)(3)Fe(S(t)Bu)(micro-S(t)Bu)(2)Ni(CO)(SDmp), 3, or (CO)(3)Fe(S(t)Bu)(micro-S(t)Bu)(2)Ni(CN(t)Bu)(SDmp), 4, respectively. One of the CO bands of 3, appearing at 2055 cm(-1) in the infrared spectrum, was assigned as the Ni-CO band, and this frequency is comparable to those observed for the CO-inhibited forms of [NiFe] hydrogenase. Like the CO-inhibited forms of [NiFe] hydrogenase, the coordination of CO at the nickel site of 1 is reversible, while the CN(t)Bu adduct 4 is more robust.

• Evidence for a Rapid Degenerate Hetero-Cope-Type Rearrangement in [Cp*W(S)(2)S-CH(2)-CH==CH(2)].

  Authors: Florian Eweiner, Shunsuke Senda, Klaus Bergander, Christian Mück-Lichtenfeld, Stefan Grimme, Roland Fröhlich, Michiko Aoyama, Hiroyuki Kawaguchi, Yasuhiro Ohki, Tsuyoshi Matsumoto, Gerald Kehr, Kazuyuki Tatsumi, Gerhard Erker

  Chemistry, an Asian journal. 11/2009;

  Treatment of the salt [PPh(4)](+)[Cp*W(S)(3)](-) (6) with allyl bromide gave the neutral complex [Cp*W(S)(2)S-CH(2)-CH==CH(2)] (7). The product 7 was characterized by an X-ray crystal structureTreatment of the salt [PPh(4)](+)[Cp*W(S)(3)](-) (6) with allyl bromide gave the neutral complex [Cp*W(S)(2)S-CH(2)-CH==CH(2)] (7). The product 7 was characterized by an X-ray crystal structure analysis. Complex 7 features dynamic NMR spectra that indicate a rapid allyl automerization process. From the analysis of the temperature-dependent NMR spectra a Gibbs activation energy of DeltaG( not equal) (278 K) approximately 13.7+/-0.1 kcal mol(-1) was obtained [DeltaH( not equal) approximately 10.4+/-0.1 kcal mol(-1); DeltaS( not equal) approximately -11.4 cal mol(-1) K(-1)]. The DFT calculation identified an energetically unfavorable four-membered transition state of the "forbidden" reaction and a favorable six-membered transition state of the "Cope-type" allyl rearrangement process at this transition-metal complex core.

• Synthesis, Structures, and Electronic Properties of [8Fe-7S] Cluster Complexes Modeling the Nitrogenase P-Cluster.

  Authors: Yasuhiro Ohki, Motosuke Imada, Ayuro Murata, Yusuke Sunada, Shun Ohta, Masaru Honda, Takahiro Sasamori, Norihiro Tokitoh, Motomi Katada, Kazuyuki Tatsumi

  Journal of the American Chemical Society. 09/2009;

  High-yield synthesis of the iron-sulfur cluster [{N(SiMe(3))(2)}{SC(NMe(2))(2)}Fe(4)S(3)](2)(mu(6)-S) {mu-N(SiMe(3))(2)}(2) (1), which reproduces the [8Fe-7S] core structure of the nitrogenaseHigh-yield synthesis of the iron-sulfur cluster [{N(SiMe(3))(2)}{SC(NMe(2))(2)}Fe(4)S(3)](2)(mu(6)-S) {mu-N(SiMe(3))(2)}(2) (1), which reproduces the [8Fe-7S] core structure of the nitrogenase P(N)-cluster, has been achieved via two pathways: (1) Fe{N(SiMe(3))(2)}(2) + HSTip (Tip = 2,4,6-(i)Pr(3)C(6)H(2)) + tetramethylthiourea (SC(NMe(2))(2)) + elemental sulfur (S(8)); and (2) Fe(3){N(SiMe(3))(2)}(2)(mu-STip)(4) (2) + HSTip + SC(NMe(2))(2) + S(8). The thiourea and terminal amide ligands of 1 were found to be replaceable by thiolate ligands upon treatment with thiolate anions and thiols at -40 degrees C, respectively, and a series of [8Fe-7S] clusters bearing two to four thiolate ligands have been synthesized and their structures were determined by X-ray analysis. The structures of these model [8Fe-7S] clusters all closely resemble that of the reduced form of P-cluster (P(N)) having 8Fe(II) centers, while their 6Fe(II)-2Fe(III) oxidation states correspond to the oxidized form of P-cluster (P(OX)). The cyclic voltammograms of the [8Fe-7S] clusters reveal two quasi-reversible one-electron reduction processes, leading to the 8Fe(II) state that is the same as the P(N)-cluster, and the synthetic models demonstrate the redox behavior between the two major oxidation states of the native P-cluster. Replacement of the SC(NMe(2))(2) ligands in 1 with thiolate anions led to more negative reduction potentials, while a slight positive shift occurred upon replacement of the terminal amide ligands with thiolates. The clusters 1, (NEt(4))(2)[{N(SiMe(3))(2)}(SC(6)H(4)-4-Me)Fe(4)S(3)](2)(mu(6)-S){mu-N(SiMe(3))(2)}(2) (3a), and [(SBtp){SC(NMe(2))(2)}Fe(4)S(3)](2)(mu(6)-S){mu-N(SiMe(3))(2)}(2) (5; Btp = 2,6-(SiMe(3))(2)C(6)H(3)) are EPR silent at 4-100 K, and their temperature-dependent magnetic moments indicate a singlet ground state with antiferromagnetic couplings among the iron centers. The (57)Fe Mossbauer spectra of these clusters are consistent with the 6Fe(II)-2Fe(III) oxidation state, each exhibiting two doublets with an intensity ratio of ca. 1:3, which are assignable to Fe(III) and Fe(II), respectively. Comparison of the quadrupole splittings for 1, 3a, and 5 has led to the conclusion that two Fe(III) sites of the clusters are the peripheral iron atoms.

• Dinuclear nickel complexes modeling the structure and function of the acetyl CoA synthase active site.

  Authors: Mikinao Ito, Mai Kotera, Tsuyoshi Matsumoto, Kazuyuki Tatsumi

  Proceedings of the National Academy of Sciences of the United States of America. 08/2009; 106(29):11862-6.

  A dinuclear nickel complex with methyl and thiolate ligands, Ni(dadt(Et))Ni(Me)(SDmp) (2), has been synthesized as a dinuclear Ni(d)-Ni(p)-site model of acetyl-CoA synthase (ACS) (dadt(Et) isA dinuclear nickel complex with methyl and thiolate ligands, Ni(dadt(Et))Ni(Me)(SDmp) (2), has been synthesized as a dinuclear Ni(d)-Ni(p)-site model of acetyl-CoA synthase (ACS) (dadt(Et) is N,N'-diethyl-3,7-diazanonane-1,9-dithiolate; Dmp is 2,6-dimesitylphenyl). Complex 2 was prepared via 2 methods: (i) ligand substitution of a dinuclear Ni(II)-Ni(II) cation complex [Ni(dadt(Et)) Ni(tmtu)2] (OTf)2 (1) with MeMgBr and KSDmp (tmtu is tetramethylthiourea), (ii) methyl transfer from methylcobaloxime Co(dmgBF2)2(Me)(Py) (5) to a Ni(II)-Ni(0) complex such as [Ni(dadt(Et))Ni(cod)] (3), generated in situ from Ni(dadt(Et)) and Ni(cod)(2), followed by addition of KSDmp (cod is 1,5-cyclooctadiene; dmgBF2 is difluoroboryl-dimethylglyoximate). Method ii models the formation of Nip-Me species proposed as a plausible intermediate in ACS catalysis. The reaction of 2 with excess CO affords the acetylthioester CH3C(O)SDmp (8) with concomitant formation of Ni(dadt(Et))Ni(CO)2 (9) and Ni(CO)4 plus Ni(dadt(Et)). When complex 2 is treated with 1 equiv of CO in the presence of excess 1,5-cyclooctadiene, the formation of 9 and Ni(CO)4 is considerably suppressed, and instead the dinuclear Ni(II)-Ni(0) complex is generated in situ, which further affords 2 upon successive treatment with Co(dmgBF2)2(Me)(Py) (5) and KSDmp. These results suggest that (i) ACS catalysis could include the Nid(II)-Nip(0) state as the active species, (ii) The Nid(II)-Nip(0) species could first react with methylcobalamin to afford Nid(II)-Nip(II)-Me, and (iii) CO insertion into the Nip-Me bond and the successive reductive elimination of acetyl-CoA occurs immediately when CoA is coordinated to the Nip site to form the active Nid(II)-Nip(0) species.

• C-H Bond Activation of Decamethylcobaltocene Mediated by a Nitrogenase Fe(8)S(7) P-Cluster Model.

  Authors: Yasuhiro Ohki, Ayuro Murata, Motosuke Imada, Kazuyuki Tatsumi

  Inorganic chemistry. 05/2009;

  A C-H bond of Cp*(2)Co was found to be cleaved by a [Fe(8)S(7)] cluster model of the nitrogenase P-cluster. This is the first example of C-H bond activation mediated by a biologically relevant Fe/SA C-H bond of Cp*(2)Co was found to be cleaved by a [Fe(8)S(7)] cluster model of the nitrogenase P-cluster. This is the first example of C-H bond activation mediated by a biologically relevant Fe/S cluster. The reaction mechanism probably consists of electron transfer from Cp*(2)Co to the [Fe(8)S(7)] cluster and subsequent proton abstraction by the reduced form of the cluster.