- Synthesis and electrosynthesis of bis-silylated cyclopentadienylniobium(V) cationic complexes. Their reactions and structural characterization
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Chemical oxidation of complexes Nb(η5-C5H4SiMe3)2X2, X = Cl (1), Br (2), I (3), with ferrocenium hexafluorophosphate in dichloromethane gives the cationic complexes 5-C5H4SiMe3)2X2>+ PF6-, X = Cl (4), Br (5
- Antinolo, Antonio,Fajardo, Mariano,Otero, Antonio,Mugnier, Yves,Nabaoui, Hassane,Mourad, Houssef
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Read Online
- Photoresist based on metallocene compound and preparation method and application thereof
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The invention belongs to the technical field of photoresist, and particularly relates to a photoresist based on a metallocene compound as well as a preparation method and application of the photoresist. The metallocene compound disclosed by the invention adopts metal as a central core structure, so that the metallocene compound has a relatively high melting point and glass-transition temperature, can meet the requirements of a photoetching technology, and is stable in structure, and a film structure is not changed during high-temperature baking. In addition, the photoresist composition provided by the invention can be used in modern photoetching processes such as 248nm photoetching, 193nm photoetching, extreme ultraviolet (EUV) photoetching, nanoimprint lithography (NIL), electron beam lithography (EBL) and the like, and is particularly suitable for being used in an extreme ultraviolet (EUV) photoetching process.
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Paragraph 0067; 0073; 0076-0077
(2021/05/26)
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- Reactions of Ferrocenium Hexafluorophosphate with P?OR Nucleophiles Give Ring C?H Functionalization or Ring Replacement Products Depending on the Phosphorus Reagent
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Ferrocenium hexafluorophosphate reacts with different P?OR nucleophiles (PR3) in CH2Cl2 at room temperature to give either half-sandwich complexes [CpFe(PR3)3](PF6) (PR3=P(OMe)3, P(OEt)3, PhP(OMe)2) or ferrocenylphosphonium salts [CpFe(C5H4PR3)](PF6) (PR3=iPr2P(OMe), iPr2P(OEt)). Mixtures of both products are formed for some other nucleophiles (PR3=Ph2P(OMe), Ph2P(OEt), PhP(OiPr)2). The mechanism of the former reaction was established using DFT calculations. This reaction pathway is especially characteristic of π-acceptor nucleophiles, which is presumably explained by their ability to stabilize the 19e intermediates. The result of the reaction with tertiary phosphines, aminophosphines, and P?OR nucleophiles can be reliably predicted based on the values of the Tolman electronic parameter (below 2070 cm?1 – only ferrocenylphosphonium salt, in between 2073 cm?1 and 2080 cm?1 – only half-sandwich complex, and in the range from 2070 cm?1 to 2073 cm?1 – mixtures of both products).
- Chamkin, Aleksandr A.,Krivykh, Vasily V.,Kreindlin, Arkady Z.,Dolgushin, Fedor M.,Ustynyuk, Nikolai A.
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supporting information
p. 1601 - 1610
(2021/04/16)
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- Iodoferrocene as a partner inN-arylation of amides
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In this study, we developed a convenient methodology for theN-arylation of various acetamides, benzamides and related compounds by iodoferrocene. Optimization of the reaction was first performed from acetamide on the basis of the achievements in the benzene series. Next, the identified conditions (use of copper(i) iodide,N,N′-dimethylethylenediamine, tripotassium phosphate in dioxane at 90 °C for 14 h) were applied to different aliphatic/aromatic primary and cyclic/acyclic secondary amides in order to determine the scope of the reaction, thus easily generating a small library of ferrocene amides.
- Kadari, Lingaswamy,Erb, William,Roisnel, Thierry,Radha Krishna, Palakodety,Mongin, Florence
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p. 15928 - 15941
(2020/10/08)
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- Imidazolium Cyclopentadienide Salts and their Use as Cp-Transfer Reagents
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The reaction of N-heterocyclic carbenes, 1a–c, towards cyclopentadienes, 2a–c, was studied. N,N′-diisopropyl-substituted carbene 1a acts as a Br?nsted base and deprotonates cyclopentadiene, 2a, and isopropylcyclopentadiene, 2b, to yield the corresponding imidazolium cyclopentadienide salts, 3a,b, whereas there is no reaction towards 1,2,3,4,5-pentamethylcyclopentadiene. Imidazolium cyclopentadienide salts, 3a,b, were characterized in solution by 1H and 13C NMR spectroscopy, as well as in the solid state by single-crystal X-ray diffraction. In addition, it was demonstrated that imidazolium cyclopentadienide salt 3a can be used as a Cp-transfer reagent in the synthesis of different cyclopentadienyl transition metal complexes.
- Bischoff, Inga-Alexandra,Müller, Carsten,Huch, Volker,Zimmer, Michael,Sch?fer, André
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p. 1941 - 1944
(2019/04/03)
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- Naphthocage: A Flexible yet Extremely Strong Binder for Singly Charged Organic Cations
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We report a quite flexible naphthol-based cage (so-called "naphthocage") which adopts a self-inclusion conformation in its free state and is able to bind singly charged organic cations extremely strongly (Ka > 107 M-1). Ion-selective electrodes prepared with this naphthocage show a super-Nernstian response to acetylcholine. In addition, the highly stable complex (1010 M-1) between ferrocenium and the naphthocage can be switched electrochemically, which lays a basis for its application in stimuli-responsive materials.
- Jia, Fei,Hupatz, Henrik,Schr?der, Hendrik V.,Witte, Felix,Paulus, Beate,Schalley, Christoph A.,Yang, Liu-Pan,Li, Dong-Hao,Xin, Shan,Xie, Xiaojiang,Jiang, Wei,Lentz, Dieter
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supporting information
p. 4468 - 4473
(2019/04/25)
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- Reaction of ferrocenium ion with secondary phosphines: replacement of cyclopentadienyl ligand rather than its C—H functionalization
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The reactions of ferrocenium salts with secondary phosphines Ph2PH, Cy2PH, and Et2PH proceed as replacement of the cyclopentadienyl ring to afford half-sandwich complexes [C5H5Fe(R2PH)3](X) (X = PF6, BF4) rather than ferrocenylphosphonium salts [C5H5FeC5H4— (PHR2)](X).
- Chamkin,Krivykh,Shtel′tser,Utegenov,Dolgushin,Ustynyuk
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p. 1380 - 1383
(2019/08/12)
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- Oxidation of Iron Complex with NHC Ligand with Molecular Iodine
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Abstract: Complex (η5-C5H5)2Fe2(CO)4 (I) reacts with 1,3-dimethylimidazolium-2-carboxylate Me2ImCO2 to give asymmetric binuclear carbene iron complex (η5-C5H5)2Fe2(CO)3(Me2Im) (II) (Me2Im = 1,3-dimethylimidazol-2-ylidene). The oxidation of compound II with elemental iodine proceeds via two mechanisms, symmetrical and asymmetrical, to form four products: (η5-C5H5Fe(CO)2(Me2Im)I (III), (η5-C5H5)Fe(CO)2I (IV), (η5-C5H5Fe(CO)2(Me2Im)I3 (V), and ferrocene (VI). In each case, two pairs of reaction products have formed, two of which include NHC ligand: neutral iron(III) complex and ionic complex V. Optimal synthesis conditions to obtain preferably one of these complexes have been found. Geometry and transition state energy of supposed reaction mechanism have been calculated by quantum chemistry methods.
- Shapovalov,Tikhonova,Skabitskii,Kolos,Sakharov,Torubaev, Yu. V.
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p. 1418 - 1423
(2019/12/25)
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- Effect of ring size on the properties of μ3-Cycloalkyne complexes: Synthesis of triruthenium complexes containing a perpendicularly coordinated μ3-Allenyl ligand
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A series of triruthenium complexes, [{Cp*Ru(μ-H)}3(μ3-η2:η2-CnH2n-4)] (2a, n = 6; 2b, n = 7; 2c, n = 8), containing a triply bridgin cycloalkyne ligand was synthesized. Although no noticeable differences were detected in the ground state, the rate of dynamic motion of the cycloalkyne ligand increased remarkably as the ring size increased. Owing to the flexibility of the larger rings, an allylic C–H bond can interact with one of the metal centers, stabilizing the transition state of the dynamic process. This interaction also caused allylic C–H bond scission upon chemical oxidation. In the case of 2b and 2c, a cationic μ3-η2:η2:η2-allenyl complex, [{Cp*Ru(μ-H)}3(μ3-η2:η2:η2-CnH2n-5)]+ (3b, n = 7; 3c, n = 8), was obtained. X-ray diffraction studies of 3 clearly show that the allenyl group is coordinated to one of the Ru-Ru bonds in a perpendicular fashion, unlike the known “parallel” μ3-allenyl complexes. In contrast to the reactions of 2b and 2c, chemical oxidation of 2a occurred via the incorporation of adventitious H2O rather than intramolecular C-H bond cleavage. Consequently, cationic μ3-cyclohexyne-μ-hydroxo complex, [{Cp*Ru(μ-H)}3(μ-OH)(μ3-η2-C6H8)]+ (5a) was obtained in 38% yield by the reaction with 2 equiv [Cp2Fe]+ in the presence of excess water. These results clearly show that the reaction pathway of the μ3-cycloalkyne complex varies with the ring size.
- Saito, Moeko,Kojima, Shuhei,Inagaki, Akiko,Seki, Koichi,Takao, Toshiro
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- Functional Synthetic Model for the Lanthanide-Dependent Quinoid Alcohol Dehydrogenase Active Site
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The oxidation of methanol by dehydrogenase enzymes is an essential part of the bacterial methane metabolism cycle. The recent discovery of a lanthanide (Ln) cation in the active site of the XoxF dehydrogenase represents the only example of a rare-earth element in a physiological role. Herein, we report the first synthetic, functional model of Ln-dependent dehydrogenase and its stoichiometric and catalytic dehydrogenation of a benzyl alcohol. Density functional theory calculations implicate a hydride transfer mechanism for these reactions.
- McSkimming, Alex,Cheisson, Thibault,Carroll, Patrick J.,Schelter, Eric J.
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supporting information
p. 1223 - 1226
(2018/02/09)
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- Sandwich complexes of iron and ruthenium with the semiconducting aromatic hydrocarbon picene
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Pentacyclic aromatic hydrocarbon picene C22H14 was synthesized by the improved two-step procedure from 1-naphthaldehyde in ca. 50% total yield. Reaction of picene with ferrocene in the presence of AlCl3 produced the binucl
- Shved, Andrei M.,Nelyubina, Yulia V.,Perekalin, Dmitry S.
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- Frustrated Lewis pairs incorporating the bifunctional Lewis acid 1,1′-fc{B(C6F5)2}2: Reactivity towards small molecules
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Applications of the bifunctional ferrocenediyl Lewis acid 1,1′-fc{B(C6F5)2}2 in frustrated Lewis pair (FLP) chemistry are described. The coordination (or otherwise) of a range of sterically encumbered C-, N- and P-centred Lewis bases has been investigated, with lutidine, tetramethylpiperidine, PPh3, PtBu3 and the expanded ring carbene 6Dipp being found to be sterically incapable of coordinate bond formation. The chemistry of a range of these FLPs in the presence of H2O, NH3, CO2 and cyclohexylisocyanate (CyNCO) has been investigated, with the patterns of reactivity identified including simple coordination chemistry, E-H bond cleavage and C-B insertion.
- Tirfoin, Rémi,Gilbert, Jessica,Kelly, Michael J.,Aldridge, Simon
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p. 1588 - 1598
(2018/02/09)
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- Catalytic Activity of Thiolate-Bridged Diruthenium Complexes Bearing Pendent Ether Moieties in the Oxidation of Molecular Dihydrogen
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Thiolate-bridged diruthenium complexes bearing pendent ethers have been found to work as effective catalysts toward the oxidation of molecular dihydrogen into protons and electrons in water. The pendent ether moiety in the complex plays an important role to facilitate the proton transfer between the metal center and the external proton acceptor.
- Yuki, Masahiro,Sakata, Ken,Kikuchi, Shoma,Kawai, Hiroyuki,Takahashi, Tsuyoshi,Ando, Masaki,Nakajima, Kazunari,Nishibayashi, Yoshiaki
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supporting information
p. 1007 - 1012
(2017/02/05)
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- Dicationic Thiolate-Bridged Diruthenium Complexes for Catalytic Oxidation of Molecular Dihydrogen
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Dicationic thiolate-bridged diruthenium complexes bearing sterically bulky alkane substituents on the thiolate ligands such as [Cp?Ru(μ-SiPr)2Ru(OH2)Cp?](OTf)2 have been found to work as effective catalysts toward oxidation of molecular dihydrogen into protons and electrons in protic solvents such as water and methanol. DFT calculations indicate that the sterically bulky alkane substituent in the complex plays an important role in facilitating the reaction step of the coordination of molecular dihydrogen.
- Yuki, Masahiro,Sakata, Ken,Nakajima, Kazunari,Kikuchi, Syoma,Sekine, Shinobu,Kawai, Hiroyuki,Nishibayashi, Yoshiaki
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supporting information
p. 4499 - 4506
(2017/12/05)
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- Synthesis and reactivity of a water-soluble NiRu monohydride complex with a tethered pyridine moiety
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We report the synthesis, characterization, and reactivity of a NiRu monohydride complex with a pyridine-bound hexamethylbenzene ligand. We investigate the mechanistic insights it provides on the H2-activation of [NiFe]hydrogenase.
- Matsumoto, Takahiro,Yoshimoto, Koji,Zheng, Chunbai,Shomura, Yasuhito,Higuchi, Yoshiki,Nakai, Hidetaka,Ogo, Seiji
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supporting information
p. 197 - 199
(2016/03/01)
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- Oxidatively Triggered Carbon-Carbon Bond Formation in Ene-amide Complexes
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Ene-amides have been explored as ligands and substrates for oxidative coupling. Treatment of CrCl2, Cl2Fe(PMe3)2, and Cl2Copy4 with 2 equiv of {(2,6-iPr2C6H3)(1-cHexenyl)N}Li afforded pseudosquare planar {3-C,C,N-(2,6-iPr2C6H3)(1-cHexenyl)N}2Cr (1-Cr, 78%), trigonal {(2,6-iPr2C6H3)(1-cHexenyl)N}2Fe(PMe3) (2-Fe, 80%), and tetrahedral {(2,6-iPr2C6H3)(1-cHexenyl)N}2Co(py)2 (3-Co, 91%) in very good yields. The addition of CrCl3 to 1-Cr, and FeCl3 to 2-Fe, afforded oxidatively triggered C-C bond formation as rac-2,2′-di(2,6-iPr2C6H3N - )2dicyclohexane (EA2) was produced in modest yields. Various lithium ene-amides were similarly coupled, and the mechanism was assessed via stoichiometric reactions. Some ferrous compounds (e.g., 2-Fe, FeCl2) were shown to catalyze C-arylation of {(2,6-iPr2C6H3)(1-cHexenyl)N}Li with PhBr, but the reaction was variable. Structural characterizations of 1-Cr, 2-Fe, and 3-Co are reported.
- Jacobs, Brian P.,Wolczanski, Peter T.,Lobkovsky, Emil B.
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supporting information
p. 4223 - 4232
(2016/05/24)
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- HYDROGEN OXIDATION CATALYST
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The present invention is to provide a hydrogen oxidation catalyst that does not contain platinum. Disclosed is a hydrogen oxidation catalyst that is a dinuclear transition metal complex having a chemical structure represented by the following general formula (1) or (2): wherein, in the general formulae (1) and (2), M1 and M2 are each independently Fe or Ru; Ar1 and Ar2 are each independently a cyclopentadienyl group or a pentamethylcyclopentadienyl group; Ar3 and Ar4 are each independently a divalent aromatic hydrocarbon group having 6 to 12 carbon atoms; and Ar5 is a monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms, and in the general formula (2), R1 and R2 are each independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms.
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Paragraph 0050
(2017/01/09)
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- Thiolate-bridged dinuclear ruthenium and iron complexes as robust and efficient catalysts toward oxidation of molecular dihydrogen in protic solvents
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Thiolate-bridged dinuclear ruthenium and iron complexes are found to work as efficient catalysts toward oxidation of molecular dihydrogen in protic solvents such as water and methanol under ambient reaction conditions. Heterolytic cleavage of the coordinated molecular dihydrogen at the dinuclear complexes and the sequential oxidation of the produced hydride complexes are involved as key steps to promote the present catalytic reaction. The catalytic activity of the dinuclear complexes toward the chemical oxidation of molecular dihydrogen achieves up to 10000 TON (turnover number), and electrooxidation of molecular dihydrogen proceeds quite rapidly. The result of the density functional theory (DFT) calculation on the reaction pathway indicates that a synergistic effect between the two ruthenium atoms plays an important role to realize the catalytic oxidation of molecular dihydrogen efficiently. The present dinuclear ruthenium complex is found to work as an efficient organometallic anode catalyst for the fuel cell. It is noteworthy that the present dinuclear complex worked not only as an effective catalyst toward chemical and electrochemical oxidation of molecular dihydrogen but also as a good anode catalyst for the fuel cell. We consider that the result described in this paper provides useful and valuable information to develop highly efficient and low-cost transition metal complexes as anode catalysts in the fuel cell.
- Yuki, Masahiro,Sakata, Ken,Hirao, Yoshifumi,Nonoyama, Nobuaki,Nakajima, Kazunari,Nishibayashi, Yoshiaki
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supporting information
p. 4173 - 4182
(2015/04/14)
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- The titanium tris-anilide cation [Ti(N[tBu]Ar)3]+ stabilized as its perfluoro-tetra-phenylborate salt: Structural characterization and synthesis in connection with redox activity of 4,4′-bipyridine dititanium complexes
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This work explores the reduction of 4,4′-bipyridine using two equivalents of the titanium(iii) complex Ti(N[tBu]Ar)3 resulting in formation of a black, crystalline complex, (4,4′-bipy){Ti(N[tBu]Ar)3}2, for which an X-ray structure determination is reported. The neutral, black, 4,4′-bipyridine-bridged bimetallic was found to be redox active, with mono- and di-anions being accessible electrochemically, and with the mono- and di-cations also being accessible chemically, and isolable, at least when using the weakly coordinating anion [B(C6F5)4]- as the counter-ion. It proved possible to crystallize the salt [(4,4′-bipy){Ti(N[tBu]Ar)3}2][B(C6F5)4]2 for a single-crystal X-ray structure investigation; in this instance it was revealed that the aromaticity of the 4,4′-bipyridine ligand, that had been disrupted upon reduction, had been regained. A rare cationic d0 metal tris-amide complex, shown by X-ray crystallography to contain an intriguing pyramidal TiN3 core geometry, namely {Ti(N[tBu]Ar)3}+, could also be isolated when using [B(C6F5)4] as the essentially non-interacting counter-ion. This highly reactive cation should be considered as a potential intermediate in the plethora of reactions wherein Ti(N[tBu]Ar)3 has been shown to effect the reduction of substrates including halogenated organic molecules, carbonyl compounds, organic nitriles, and metal complexes. This journal is
- Spinney, Heather A.,Clough, Christopher R.,Cummins, Christopher C.
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p. 6784 - 6796
(2015/04/14)
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- Organometallic nickel(III) complexes relevant to cross-coupling and carbon-heteroatom bond formation reactions
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Nickel complexes have been widely employed as catalysts in C-C and C-heteroatom bond formation reactions. In addition to Ni(0) and Ni(II) intermediates, several Ni-catalyzed reactions are proposed to also involve odd-electron Ni(I) and Ni(III) oxidation states. We report herein the isolation, structural and spectroscopic characterization, and organometallic reactivity of Ni(III) complexes containing aryl and alkyl ligands. These Ni(III) species undergo transmetalation and/or reductive elimination reactions to form new C-C or C-heteroatom bonds and are also competent catalysts for Kumada and Negishi cross-coupling reactions. Overall, these results provide strong evidence for the direct involvement of organometallic Ni(III) species in cross-coupling reactions and oxidatively induced C-heteroatom bond formation reactions.
- Zheng, Bo,Tang, Fengzhi,Luo, Jia,Schultz, Jason W.,Rath, Nigam P.,Mirica, Liviu M.
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supporting information
p. 6499 - 6504
(2014/05/20)
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- Insight into one-electron oxidation of the {Fe(NO)2}9 dinitrosyl iron complex (DNIC): Aminyl radical stabilized by [Fe(NO) 2] motif
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A reversible redox reaction ({Fe(NO)2}9 DNIC [(NO)2Fe(N(Mes)(TMS))2]- (4) ? oxidized-form DNIC [(NO)2Fe(N(Mes)(TMS))2] (5) (Mes = mesityl, TMS = trimethylsilane)), characterized by IR, UV-vis, 1H/15N NMR, SQUID, XAS, single-crystal X-ray structure, and DFT calculation, was demonstrated. The electronic structure of the oxidized-form DNIC 5 (Stotal = 0) may be best described as the delocalized aminyl radical [(N(Mes)(TMS))2]2 -? stabilized by the electron-deficient {Fe III(NO-)2}9 motif, that is, substantial spin is delocalized onto the [(N(Mes)(TMS))2] 2-? such that the highly covalent dinitrosyl iron core (DNIC) is preserved. In addition to IR, EPR (g ≈ 2.03 for {Fe(NO) 2}9), single-crystal X-ray structure (Fe-N(O) and N-O bond distances), and Fe K-edge pre-edge energy (7113.1-7113.3 eV for {Fe(NO) 2}10 vs 7113.4-7113.9 eV for {Fe(NO)2} 9), the 15N NMR spectrum of [Fe(15NO) 2] was also explored to serve as an efficient tool to characterize and discriminate {Fe(NO)2}9 (δ 23.1-76.1 ppm) and {Fe(NO)2}10 (δ -7.8-25.0 ppm) DNICs. To the best of our knowledge, DNIC 5 is the first structurally characterized tetrahedral DNIC formulated as covalent-delocalized [{FeIII(NO-) 2}9-[N(Mes)(TMS)]2-?]. This result may explain why all tetrahedral DNICs containing monodentate-coordinate ligands isolated and characterized nowadays are confined in the {Fe(NO) 2}9 and {Fe(NO)2}10 DNICs in chemistry and biology.
- Tsou, Chih-Chin,Tsai, Fu-Te,Chen, Huang-Yeh,Hsu, I-Jui,Liaw, Wen-Feng
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p. 1631 - 1639
(2013/04/10)
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- Dehydrogenation of alcohols by bis(phosphinite) benzene based and bis(phosphine) ruthenocene based iridium pincer complexes
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Dehydrogenation of alcohols by three iridium pincer complexes, IrH(Cl)[2,6-(tBu2PO)2C6H 3] (1), {IrH(acetone)[2,6-(tBu2PO) 2C6H3]}{BF4} (2), and IrH(Cl)[{2,5-(tBu2PCH2)2C 5H2}Ru(C5H5)] (3), is reported, in both the presence and the absence of a sacrificial hydrogen acceptor. Dehydrogenation of secondary alcohols proceeds in a catalytic mode with turnover numbers up to 3420 (85% conversion) for acceptorless dehydrogenation of 1-phenylethanol. Primary alcohols are readily decarbonylated even at room temperature to give catalytically inactive 16e Ir-CO adducts. The mechanism of this transformation was studied in detail, especially for EtOH; new intermediates were isolated and characterized.
- Polukeev, Alexey V.,Petrovskii, Pavel V.,Peregudov, Alexander S.,Ezernitskaya, Mariam G.,Koridze, Avthandil A.
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p. 1000 - 1015
(2013/05/08)
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- A heterobimetallic approach to stabilize the elusive disulfur radical trianion ( subsulfide ) S23-
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A unique heterobimetallic disulfur monoradical, complex 2, with a diamond-shaped {NiS2Pt} core has been synthesized by two-electron reduction of a supersulfido-(nacnac)nickel(II) complex (nacnac=β- diketiminato) with [Pt(Ph3P)2(η2-C 2H4)] as a platinum(0) source and isolated in 82 % yield. Strikingly, the results of DFT calculations in accordance with spectroscopic (EPR, paramagnetic NMR) and structural features of the complex revealed that the bonding situation of the S2 ligand is between the elusive half-bonded S2 radical trianion (S2 3-) and two separated S2- ligands. Accordingly, the NiII center is partially oxidized, whereas the PtII site is redox innocent. The complex can be reversibly oxidized to the corresponding Ni,Pt-disulfido monocation, compound 3, with a S-S single bond, and reacts readily with O2 to form the corresponding superoxonickel(II) and disulfidoplatinum(II) (4) complexes. These compounds have been isolated in crystalline form and fully characterized, including IR and multi-nuclear NMR spectroscopy as well as ESI mass spectrometry. The molecular structures of compounds 2-4 have been confirmed by single-crystal X-ray crystallography. Copyright
- Yao, Shenglai,Hrobarik, Peter,Meier, Florian,Rudolph, Robert,Bill, Eckhard,Irran, Elisabeth,Kaupp, Martin,Driess, Matthias
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p. 1246 - 1253
(2013/03/14)
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- Formal insertion of o-carborynes into ferrocenyl C-H bonds: A simple access to o-carboranylferrocenes
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Insertion of o-carborynes (1,2-dehydro-o-carboranes) into ferrocenyl C-H bonds has been described, providing a convenient methodology for the preparation of functionalized ferrocenyl o-carboranes. Reaction of the carboryne precursors 1-I-2-Li-9,12-Me2-1,2-C2B10H8 or 1-I-2-Li-3-R-1,2-C2B10H9 (R = H, Ph, Me, Cl, Br, and I) with 2.5 equiv of ferrocene at 80 °C in cyclohexane afforded [1-(η5-C5H4)(9,12-Me2-1,2-C 2B10H9)]Fe(η5-C 5H5) and [1-(η5-C5H 4)(3-R-1,2-C2B10H10)] Fe(η5-C5H5) (R = H, Ph, Me, Cl, Br, and I) in 19-44% isolated yields. On the other hand, in addition to the desired C-H bond insertion products [1-(η5-C5H4)(3-X-1, 2-C2B10H10)]Fe(η5-C 5H5), bis(ferrocenyl)-o-carboranes 1,2- [(η5-C5H5)Fe(η5-C 5H4)]2-3-X-1,2-C2B 10H9 were isolated from the reactions of 1-I-2-Li-3-X-1,2-C2B10H9 (X = Cl, Br, and I) in 12%, 15%, and 8% yields, respectively. Treatment of 1,2-dilithio-o-carborane or 1-lithio-2-methyl-o-carborane with ferrocenium hexafluorophosphate in cyclohexane also generated [1-(η5-C5H 4)(1,2-C2B10H11)] Fe(η5-C5H5) and [1-(η5- C5H4)(2-Me-1,2-C2B10H 10)]Fe(η5-C5H5) in 17% and 31% isolated yields, respectively. On the basis of these observations, it is suggested that the single-electron oxidation of ferrocene to the electrophilic ferrocenium cation by o-carborynes is crucial for the insertion reaction. Accordingly, a reaction mechanism is proposed.
- Wang, Sunewang Rixin,Xie, Zuowei
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p. 4544 - 4550
(2012/07/14)
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- A Study of the reaction of iron dichloride with the pyridine activated cyclopentadiene in anhydrous 2-propanol
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A reaction was studied between iron dichloride solvate and pyridine activated cyclopentadiene in anhydrous 2-propanol. We showed that pyridine hydrochloride formed in the course of this reaction can be easily separated from the target product (ferrocene) and recycled after neutralization with sodium isopropoxide, which imparts the preparative value to the studied reaction.
- Kurbanov
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p. 1765 - 1767
(2012/01/06)
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- Synthesis and decarbonylation reactions of diiron cyclopentadienyl complexes with bent-phosphinidene bridges
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The phosphinidene complexes [Fe2Cp2(μ-PR)(μ-CO) (CO)2] (Cp = η5-C5H5; R=Cy, Ph, Mes, Mes* Mes = 2,4,6-C6H2Me3, Mes* = 2,4,6-C6H2tBu3) were readily prepared in high yields through a two-step procedure starting from the corresponding phosphine complexes [Fe2Cp2(μ-CO) 2(CO)(PH2R)]. When R = Cy, Ph, Mes, the first step required the oxidation of the phosphine complex with 1 equiv of [FeCp 2]BF4, this being followed by spontaneous dehydrogenation to yield the cationic phosphide complexes [Fe2Cp2(μ- PHR)(μ-CO)(CO)2]BF4, while the formation of the related PMes*H-bridged complex required a double oxidation of the corresponding neutral precursor in the presence of a deprotonating agent. In all cases the final step involved the deprotonation of the above cations with strong bases such as M(OH) (M = Na, K). Attempts to decarbonylate the above phosphinidene complexes by either thermolysis or photolysis in solution gave results strongly dependent on the nature of R. Thus, the photolysis of the cyclohexylphosphinidene complex gave a mixture of the clusters [Fe 4Cp4(μ3-PCy)2(μ3- CO)(μ-CO)(CO)] (Fe-Fe distances 2.6115(7) and 2.5332(8) A) and [Fe 3Cp3(μ3-PCy)(μ-PCyH)(μ-CO) 2], while the thermal decarbonylation of the mesitylphosphinidene complex in refluxing toluene gave the trinuclear derivative [Fe 3Cp3(μ-PMes)(μ-PMesH)(μ-CO)2(CO)], having a trigonal phosphinidene ligand bridging two iron atoms (Fe-P = 2.161(8), 2.165(8) A). The formation of all these compounds presumably involves the participation of the corresponding intermediate complex [Fe2Cp 2(μ-PR)(μ-CO)2], a species likely to contain a trigonal (four-electron-donor) phosphinidene ligand, not detected. In contrast, the supermesitylphosphinidene complex undergoes a C(tBu)-H oxidative addition to the P atom under mild thermal conditions to give the phosphine derivative [Fe2Cp2(μ-CO)2(CO){PH(CH 2CMe2)C6H2tBu 2}], while its photolysis gave a mixture of the above phosphine complex and the phosphide-hydride derivatives cis- and trans-[Fe 2Cp2(μ-H){μ-P(CH2CMe2)C 6H2tBu2}(CO)2], the latter resulting from the oxidative addition of a P-H bond to the dimetal center.
- Alvarez, M. Angeles,Garcia, M. Esther,Gonzalez, Rocio,Ramos, Alberto,Ruiz, Miguel A.
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p. 1102 - 1115
(2011/04/22)
-
- Oxidation of dihydrogen by iridium complexes of redox-active ligands
-
Unsaturated organoiridium complexes were prepared with amidophenolate ligands derived from 2-(2-trifluoromethyl)amino-4,6-di-tert-butylphenol (H 2tBAF) and 2-tert-butylamino-4,6-di-tert- butylphenol (H2tBAtBu). The following 16e complexes were characterized: Cp*M(tBAR) with M = Ir (1F and 1t-Bu), Rh (2F), and (cymene)Ru( tBAF) (3F). These complexes undergo two 1e oxidations at potentials of about 0 and -0.25 V vs Cp2Fe 0/+. The magnitude of δE1/2 is sensitive to the counteranions, and the reversibility is strongly affected by the presence of Lewis bases, which stabilize the oxidized derivatives. Crystallographic measurements indicate that upon oxidation the amidophenolate ligands adopt quinoid character, as indicated by increased alternation of the C-C bond lengths in the phenylene ring backbone and shortened C-N and C-O bonds. Unlike the charge-neutral precursors, the cationic [Cp*M(tBA R)]+ are Lewis acidic and form well-characterized adducts with PR3 (R = Me, Ph), CN-, MeCN (reversibly), and CO. In the absence of competing ligands, the cations oxidize H2. Coulommetry measurements indicate that H2 is oxidized by the monocations [Cp*M(tBAR)]+, not the corresponding dications. Oxidation of H2 is catalytic in the presence of a noncoordinating base at potentials required for the generation of [Cp*M(tBAR)]+. The rate decreases in the order [Cp*M(tBAF)]BArF4 > [Cp*M(tBAF)]PF6 > [Cp*M( tBAt-Bu)]PF6. The reduction of ferrocenium by H2 is catalyzed by Cp*M(tBAR).
- Ringenberg, Mark R.,Nilges, Mark J.,Rauchfuss, Thomas B.,Wilson, Scott R.
-
p. 1956 - 1965
(2010/06/14)
-
- Indirectly connected bis(N-Heterocyclic Carbene) bimetallic complexes: Dependence of metal-metal electronic coupling on linker geometry
-
Reaction of l,l',3,3'-tetra(tert-amyl)benzobis(imidazolylidene) (1) with 2 equiv of FcN3 or FcNCS afforded bisadducts [(FcN3) 2(1)] (2) or [(FcNCS)2(1)] (3), respectively (Fc = ferrocene). To the best of our kno
- Tennyson, Andrew G.,Khramov, Dimitri M.,Varnado Jr., C. Daniel,Creswell, Philip T.,Kamplain, Justin W.,Lynch, Vincent M.,Bielawski, Christopher W.
-
p. 5142 - 5147
(2010/01/06)
-
- Microwave synthesis of benchmark organo-iron complexes
-
Microwave-assisted reaction techniques have been applied to the formation of a variety of organo-iron species. The species synthesized include ferrocene and acetyferrocene, piano stool complexes such as CpFe(CO)2I, CpFe(PPh3)(CO)I, a
- Garringer, Sean M.,Hesse, Andrew J.,Magers, John R.,Pugh, Kristapher R.,O'Reilly, Stacy A.,Wilson, Anne M.
-
p. 6841 - 6844
(2010/04/01)
-
- Synthesis and reversible reductive coupling of cationic, dinitrogen-derived diazoalkane complexes
-
A series of cationic diazoalkane complexes [4-RC6H 4C(H)NNMo(N[t-Bu]Ar)3][AICI4], [1-R][AICI 4] (R = NMe2, Me,H,Br,CN; Ar = 3,5-C6H 3Me2) has been prepared
- Curley, John J.,Murahashi, Tetsuro,Cummins, Christopher C.
-
p. 7181 - 7193
(2009/12/05)
-
- Alkylation of dinitrogen in [(HIPTNCH2CH2) 3N]Mo complexes (HIPT = 3,5-(2,4,6-i-Pr3C 6H2)2C6H3
-
In this paper we explore the ethylation of dinitrogen (employing [Et 3O][BArf4]; Arf = 3,5-(CF 3)2C6H3) in [HIPTN3N]Mo (Mo) complexes ([HIPTN3N]
- Kupfer, Thomas,Schrock, Richard R.
-
p. 12829 - 12837
(2010/01/30)
-
- Redox chemistry of the triplet complex (PNP)Co
-
Reaction of PNPCo, where PNP is (tBu2PCH 2SiMe2)2N-, with the persistent radical galvinoxyl, G, gives PNPCoIIG, a nonplanar S = 3/2 species. Reaction with PhCH2Cl or with 0.5 mol I2 gives PNPCoX (X = Cl or I, respectively), but additional I2, seeking CoIII, gives instead oxidation at phosphorus: (tBu2P(I)CH 2-SiMe2NSiMe2CH2PtBu 2)Col2. Hydrogen-atom transfer reagents fail to give PNPCoH, but H2 gives instead PNPCo(H)2, a result rationalized thermodynamically based on DFT calculations. Multiple equiv of PhSiH3 give a product of Co(V), where N/SiPh and P/Si bonds have formed. N2CH(SiMe3) gives a 1:1 adduct of PNPCo, whose metric parameters suggest partial oxidation above CoI; N 2CHPh gives a 1:1 adduct but with very different spectroscopic features. PhN3 reacts fast, via several intermediates detected below 0°C, to finally release N2 and form a CoI product where one phosphorus has been oxidized, PN(P=NPh)Co. Whereas PNPCo(N 3) resists loss of N2 on heating, one electron oxidation gives a rapid loss of N2, and the remaining nitride nitrogen is quickly incorporated into the chelate ligand, giving [tBu 2PCH2SiMe2NSiMe2-NP( tBu2)=CH2Co]. O2 or PhI=O generally gives products where one or both phosphorus centers are converted to its oxide, bonded to cobalt.
- Ingleson, Michael J.,Pink, Maren,Fan, Hongjun,Caulton, Kenneth G.
-
p. 4262 - 4276
(2008/09/20)
-
- B-C bond cleavage of BArF anion upon oxidation of rhodium(I) with AgBArF. Phosphinite rhodium(I), rhodium(II), and rhodium(III) pincer complexes
-
A rare case of BArF anion cleavage (BArF- = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) by a metal complex is described. Reaction of the Rh(I) dinitrogen complexes 5a,b and 6a,b, based on the phosphinite pincer ligands {C6H4[OP( tBu)2]2} (2), with 2 equiv of AgBArF at room temperature resulted in B-C bond cleavage of one of the BArF anions and aryl transfer to afford the Rh(III) aryl complexes 7 and 8, respectively. The X-ray structure of 8 revealed a square-pyramidal geometry with a coordinated acetone molecule. The aryl transfer occurred as a result of electrophilic attack by unsaturated Rh(III) on one of the aryl rings of the BArF anion. Utilizing different solvents yielded the same product, except when CH3CN was used, in which case one-electron oxidation took place, yielding complex 9. Treatment of 6a,b with 1 equiv of AgX (X = BAr F, BF4, PF6) resulted in a one-electron oxidation to yield the paramagnetic Rh(II) complexes 9-11, respectively. Complex 11 was characterized by X-ray diffraction, revealing a mononuclear square-planar Rh(II) complex.
- Salem, Hiyam,Shimon, Linda J. W.,Leitus, Gregory,Weiner, Lev,Milstein, David
-
p. 2293 - 2299
(2009/02/01)
-
- Multiredox heterometallic carbosilane dendrimers
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A convergent growth approach for the synthesis of novel heterometallic dendritic molecules derived from carbosilane frameworks and functionalized with silicon-bridged ferrocenyl and (η6-aryl)tricarbon-ylchromium moieties has been developed. The synthetic route involves the construction of the dendritic fragments (CH2=CH)MePhSiFc (1) (Fc = (η5-C5H4)Fe(η5-C 5H5)) (CH2=CHCH2)PhSi[(CH 2)2MePhSiFc]2 (3), (CH2=CH) MeSi[{(η6-C6H5)Cr(CO)3}Fc] (4), and (CH2=CHCH2){(η6-C6H 5)Cr(CO)3}MeSi[(CH2)2- Me{(η6-C6H5)Cr(CO)3}SiFc] 2 (5), containing a single reactive C=C functionality, in addition to ferrocenyl (1 and 3) and linked ferrocenyl and (η6-C 6H5)Cr(CO)3 moieties (4 and 5) and their subsequent attachment to the tetrafunctional core Si[(CH2) 3Si(Me)2H]4 (6), via platinum-catalyzed hydrosilylation reactions. The first- and second-generation dendrimers 8 and 9, containing four and eight ferrocenyl units on the dendritic surface, respectively, have been prepared by this procedure. Thermal treatment of 8 and 9 with Cr(CO)6 afforded the targeted heterometallic dendrimers 7 and 10, carrying silicon-bridged (η5-C5H 4)Fe(η5-C5H5) and (η6-C6H5)Cr(CO)3 moieties appended at the dendrimer periphery. The molecular structures of the vinyl-functionalized silanes 1 and 4 have been determined by single-crystal X-ray diffraction. The crystal structure of 4 showed that the Cr(CO)3 group is disposed in a transoid configuration with respect to the ferrocenyl moiety. The heterobimetallic 4 also shows an interesting self-assembly of the metals (Fe and Cr) in the crystal. The electrochemical behavior of all new dendritic molecules has been investigated. For the heterometallic 4, 7, and 10 the oxidation of the iron centers becomes more anodic compared to the oxidation of the ferrocenyl units in the homometallic molecules 1, 8, and 9, due to the electron-withdrawing nature of the neighboring silicon-linked (η-C 6H5)Cr(CO)3 moieties. In addition, stable electrode surfaces modified with dendrimers 8 and 9 have been prepared.
- Zamora, Magdalena,Alonso, Beatriz,Pastor, Cesar,Cuadrado, Isabel
-
p. 5153 - 5164
(2008/10/09)
-
- A straightforward asymmetric synthesis of 1,2-disubstituted ferrocenylalkyl amines with the unusual (SFc,S) configuration
-
A useful synthesis of rare 1,2-disubstituted ferrocenylalkyl amines with (SFc,S) configuration has been achieved in a sequential one-pot methodology from (S)-p-tolylsulfinylferrocene. The Royal Society of Chemistry.
- Grach, Guillaume,Lohier, Jean-Francois,Santos, Jana Sopkova-De Oliveira,Reboul, Vincent,Metzner, Patrick
-
p. 4875 - 4877
(2008/09/17)
-
- Preparation, structure and reactivity of polynuclear gold(I) phosphanyl alkanethiolates
-
The homoleptic gold(I) thiolates of formula [Au(SR)]n, (R = CMe3, CH2CMe3, CH2CHMe2, CPh3) have been converted into their phosphane derivatives of general formula [Au(SR)-(L)] (L = PMe3, PMe2Ph, PMePh 2, PPh3) and [Au2(SR)2(dppe)] [dppe = 1,2-bis(diphenylphosphanyl)ethane], which have been characterized by elemental analysis, mass spectrometry, 1H and 31P NMR spectroscopy and cyclic voltammetry. Complexes [Au(SCMe3)(PMePh2)] (1c), [Au2(SCMe3)2(dppe)] (1e) and [Au(SCH 2CMe3)(PPh3)] (3d) have been characterized in the solid state by X-ray diffraction: no aurophilic interactions have been found. The electrochemical behaviour of these phosphane thiolato derivatives shows two irreversible oxidation processes, the first of which involves 0.5 electrons per Au-SR. Chemical oxidation by [FeCp2]BF4 produces disulfide and cationic gold(I) complexes of formula [Au 2(SR)(L)2][BF4] and [Au2(SR)(dppe)] [BF4], characterized by elemental analysis, mass spectrometry and 1H and 31P NMR spectroscopy. All the complexes are presumably dimeric in the solid state as shown in the case of [Au 4(SCMe3)2-(dppe)2][BF 4]2 (5e) and [Au4(SCH2CMe 3)2(PMe3)4][BF4] 2 (7a), which have been fully characterized by X-ray diffraction. The aurophilic interactions form a structure of four gold atoms with pairs of atoms bonded by bridging thiolato ligands, which are arranged in an almost perfect square in the case of 7a and in an unprecedented zigzag sequence in the case of 5e. Complex 4a reacts with HSCMe3 under basic conditions to give [Au(SCMe3)(PMe3)] and with LiX (X = Me, CH 2CMe3) to give a 1:1 mixture of [AuX(PMe3)] and [Au(SCMe3)(PMe3)]. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Battisti, Antonella,Bellina, Oliver,Diversi, Pietro,Losi, Serena,Marchetti, Fabio,Zanello, Piero
-
p. 865 - 875
(2008/09/18)
-
- Method for producing organo-metallic compounds of cyclopentadiene
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A method for producing ferrocene and other organometallic compounds of cyclopentadiene is disclosed. Dry iron chloride (or other selected metal salt) is added to a solution of cyclopentadiene, diethylamine, potassium and dibenzo-18-crown-6 ether in a cooled flask under a dry nitrogen atmosphere. The solution is mixed vigorously for a few hours and any excess diethylamine is evaporated. Ferrocene (or other organometallic compounds of cyclopentadiene) is extracted from the residue using petroleum ether, and any solvent is removed.
- -
-
Page/Page column 4
(2008/06/13)
-
- Oxidatively induced reactions of a diimine platinum(IV) tetramethyl complex
-
The oxidation of the Pt(IV) tetramethyl complex [Ar{single bond}N{double bond, long}CH{single bond}CH{double bond, long}N{single bond}Ar]PtMe4 (Ar = 2,6-Me2C6H3) has been investigated in acetonitrile and dichloromethane. Cyclic voltammetry demonstrates that the irreversible oxidation of [Ar{single bond}N{double bond, long}CH{single bond}CH{double bond, long}N{single bond}Ar]PtMe4 occurs at a slightly less positive oxidation potential than the irreversible oxidation of the analogous Pt(II) species [Ar{single bond}N{double bond, long}CH{single bond}CH{double bond, long}N{single bond}Ar]PtMe2. The product distribution arising from the oxidation depends strongly on the reaction conditions and includes cationic Pt(IV) species (acetonitrile, dichloromethane solvents) and Pt(II) species (dichloromethane only). Evidence is presented that suggests that homolytic cleavage of a weakened Pt{single bond}C bond in [ArN {double bond, long} CH {single bond} CH {double bond, long} NAr] PtMe4{radical dot} + is involved in the oxidatively induced reactions.
- Wik, Bror J.,Tilset, Mats
-
p. 3223 - 3230
(2008/02/09)
-
- Redox-active complexes containing group 8 metal centers linked by C 2 bridges
-
A series of complexes containing dicarbon ligands bridging redox-active group 8 metal-ligand fragments M(dppe)Cp′ (M = Fe, Ru, Os; Cp′ = Cp, Cp*) have been prepared. These complexes give up to four one-electron anodic processes at a platinum electrode, with separations of successive oxidation potentials of ca. 850 mV, giving rise to large comproportionation constants, Kc (ca. 1012). Examples of the 36-electron neutral, 35-electron monocationic, and 34-electron dicationic species, together with some related monoprotonated complexes, have been isolated. Structural studies of the 36-, 35-, and 34-electron species derived from the dicarbon complex featuring two Ru(dppe)Cp end-caps (7) show that shortening of the M - C and lengthening of the C - C bonds occur upon oxidation. A complementary spectroelectrochemical investigation has revealed an intense band near 14 300 cm-1 associated with [7]PF6, which is tentatively attributed to a Ru(d) - [Ru(d)/C2(π)]* transition, rather than a genuine IVCT band. These observations have been rationalized using DFT calculations and collectively indicate that the frontier orbitais are delocalized over both group 8 metal centers and the carbon chain.
- Bruce, Michael I.,Costuas, Karine,Ellis, Ben G.,Halet, Jean-Francois,Low, Paul J.,Moubaraki, Boujemaa,Murray, Keith S.,Ouddai, Nadia,Perkins, Gary J.,Skelton, Brian W.,White, Allan H.
-
p. 3735 - 3745
(2008/10/09)
-
- Ligand bridged heterodinuclear transition metal complexes - Syntheses, structures and electrochemical investigations
-
The syntheses of the homo- and hererobimetallic compounds [L n1M(η5-C5H4)CMe 2(η5-C9H6)2ML n] (2a-5d), [(C9H7)CMe2(η 5-C5H4)Fe(η5-C5H 4)CMe2(η5-C9H6) 2MLn] (6a-c), and [(η5-C5H 4)CMe2(η5-C9H6) 2MLn]2Fe (7a-b) are reported with 1MLn = Rh(cod) 2, Ir(cod) 3, Mn(CO)3 4 and FeCp 5, 2MLn = Rh(cod) a, Ir(cod) b, Mn(CO)3 c and FeCp d, respectively. Crystal structures of 3a, 3b and 5c are described showing two different ligand conformations in form of two rotamers. The energetic difference between these both rotamers is insignificant small in the gas phase according to DFT calculations. The rotation barrier for the species has been determined to 23 kJ/mol. According to the absence of intermolecular interactions in the solid state, the preference for one of the conformers is deduced from packing effects. All complexes are investigated by cyclic voltammetry. The shift of the redox potentials with respect to the mononuclear reference systems is a suitable tool to determine intermetallic electronic interaction. For some compounds, the normal behaviour with an increasing separation of the redox potentials is observed. A second group of complexes shows the opposite behaviour with a decreasing in the potential differences. A mechanism of intramolecular catalytic oxidation is supposed for that species.
- Gaede, Petra Escarpa,Van Wuellen, Christoph
-
p. 541 - 552
(2008/10/09)
-
- Diastereoselectivity at chiral metal center of half-sandwich-type ruthenium complexes with planar-chiral cyclopentadienyl ligands in multiple ligand transfer reaction
-
The triple ligand transfer reaction between planar-chiral cyclopentadienyl-ruthenium complexes [Cp′Ru(NCMe)3][PF6] (1) (Cp′ = 1-(COOR2)-2-Me-4-R1C5H2; R1 = Me, Ph, t-Bu) and iron
- Katayama, Taku,Onitsuka, Kiyotaka,Takahashi, Shigetoshi
-
p. 2245 - 2256
(2007/10/03)
-
- Homoleptic complexes of cobalt(0) and nickel(0,I) with 1,1′- bis(diphenylphosphino)ferrocene (dppf): Synthesis and characterization
-
Reduction of Co(dppf)Cl2 with 2 equiv of sodium naphthalenide in THF, in the presence of dppf, affords the homoleptic complex Co(dppf) 2, 1, isolated in 65% yield as a brick red solid, extremely air sensitive. In solution, under inert atmosphere, 1 slowly decomposes into Co and dppf, following a first-order kinetic law (t1/2 = 21 h at 22°C). Similarly to the Rh and Ir congeners, 1 undergoes a one-electron reversible reduction to [Co(dppf)2]-. Attempts to obtain this d 10 species by chemical as well as electrochemical reduction of 1 lead to the hydride HCo(dppf)2, 2, as the only product that can be isolated. Reduction of Ni(dppf)Cl2 with sodium in the presence of dppf and catalytic amounts of naphthalene affords Ni(dppf)2, 3, isolated in 60% yield as a yellow air stable solid. The stoichiometric oxidation of 3 with [FeCp2]PF6 forms the d9 complex [Ni(dppf)2]PF6, 4, which represents the second example of a structurally characterized Ni(I) complex stabilized by phosphines. A single-crystal X-ray analysis shows for the metal a distorted tetrahedral environment with a dihedral angle defined by the planes containing the atoms P(1), Ni, P(2) and P(3), Ni, P(4) of 78.2° and remarkably long Ni-P bond distances (2.342(3)-2.394(3) A). The EPR spectroscopic properties of 1 (at 106 K in THF) and 4 (at 7 K in 2-methyl-THF) have been examined and g tensor values measured (1, gx = 2.008, gy = 2.182, gz = 2.326; 4, gx = 2.098, gy = 2.113, gz = 2.332). A linear dependence between the hyperfine constants and the Ni-P bond distances has been evidenced. Finally, the change with time of the EPR spectrum of 4 indicates that it very slowly releases dppf.
- Pilloni, Giuseppe,Toffoletti, Antonio,Bandoli, Giuliano,Longato, Bruno
-
p. 10321 - 10328
(2008/10/09)
-
- Single-electron oxidation of monomeric copper(I) alkyl complexes: Evidence for reductive elimination through bimolecular formation of alkanes
-
Monomeric Cu(I) alkyl complexes (NHC)Cu(R) (NHC = N-heterocyclic carbene; R = Me or Et) and (dtbpe)Cu(Me) (dtbpe = 1,2-bis(di-tert-butylphosphino)ethane) have been prepared, isolated, and characterized. Single-electron oxidation of the Cu(I) alkyl complexes upon reaction with AgOTf to form putative Cu(II) intermediates of the type [(L)Cu(R)]+ (L = NHC or dtbpe, R = Me or Et) results in the rapid production of (L)Cu(X) (X = OTf) and R2. Experimental studies suggest that the reductive elimination of R2 from Cu(II) occurs through a nonradical bimolecular mechanism. Computational studies of the Cu-Cmethyl yield bond dissociation enthalpies of [(SIPr)Cu-CH3]n+ (80 kcal/mol for n = 0 {Cu(I)} and 38 kcal/mol for n = 1 (Cu(II)}).
- Goj, Laurel A.,Blue, Elizabeth D.,Delp, Samuel A.,Gunnoe, T. Brent,Cundari, Thomas R.,Petersen, Jeffrey L.
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p. 4097 - 4104
(2008/10/09)
-
- Reactivity of ferrocenium cations with molecular oxygen in polar organic solvents: Decomposition, redox reactions and stabilization
-
The behaviour of chemically or electrochemically generated ferrocenium cations has been studied in some polar organic solvents (DMF, DMSO, acetonitrile, acetone, methylene chloride) under molecular oxygen. Adducts between oxygen and ferrocenium species can differently evolve according to the solvent (oxidizable or not) and the absence or the presence of another reagent. A rapid decomposition of ferrocenium cations is observed in the absence of another substrate. In the presence of some substrates and antioxidants, the stability of ferrocenium cations towards molecular oxygen notably increases and in some cases redox reactions take place with formation of ferrocene.
- Hurvois,Moinet
-
p. 1829 - 1839
(2007/10/03)
-
- Multielectron redox chemistry of iron porphyrinogens
-
Iron octamethylporphyrinogens were prepared and structurally characterized in three different oxidation states in the absence of axial ligands and with sodium or tetrafluoroborate as the only counterions. Under these conditions, the iron- and ligand-based redox chemistry of iron porphyrinogens can be defined. The iron center is easily oxidized by a single electron (E1/2 = -0.57 V vs NHE in CH3CN) when confined within the fully reduced macrocycle. The porphyrinogen ligand also undergoes oxidation but in a single four-electron step (Ep = +0.77 V vs NHE in CH3CN); one of the ligand-based electrons is intercepted for the reduction of Fe(III) to Fe(II) to result in an overall three-electron oxidation process. The oxidation equivalents in the macrocycle are stored in Cα-C α bonds of spirocyclopropane rings, formed between adjacent pyrroles. EPR, magnetic and Moessbauer measurements, and DFT computations of the redox states of the iron porphyrinogens reveal that the reduced ligand gives rise to iron in intermediate spin states, whereas the fully oxidized ligand possesses a weaker σ-donor framework, giving rise to high-spin iron. Taken together, the results reported herein establish a metal-macrocycle cooperativity that engenders a multielectron chemistry for iron porphyrinogens that is unavailable to heme cofactors.
- Bachmann, Julien,Nocera, Daniel G.
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p. 4730 - 4743
(2007/10/03)
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- Some organometallic chemistry of molybdenum complexes that contain the [HIPTN3N]3- triamidoamine ligand, {[3,5-(2,4,6.i.Pr 3C6H2)2C6H 3NCH2CH2]3N}3-
-
Reactions between [HIPTN3N]Mo(N2) and ethylene, acetylene, or CO yield Mo(η2-C2H4), Mo(η2-C2H2), and Mo(CO), respectively ([HIPTN3N]3- = [3,5-(2,4,6-i-Pr3C 6H2)2C6H3NCH 2- CH2]3N3-; HIPT = hexaisopropylterphenyl; [HIPTN3N]Mo = Mo). All are paramagnetic C3 symmetric species. Attempts to prepare Mo(CO) through reduction of MoCl with Na/Hg in THF under carbon monoxide yielded [Mo(CO)]Na, in which the sodium ion is believed to be bound within the HIPT aryl system. Addition of a variety of acids such as [Et3NH]BAr′4 to [Mo(CO)]Na led to formation of the carbonyl hydride, Mo(CO)H, which also could be prepared by treating MoH with CO. Reactions between MoH and ethylene, 1-hexene, or 1-octene in benzene yield paramagnetic, red Mo(CH2R) complexes (CH2R = ethyl, hexyl, or octyl). MoMe could be prepared by treating MoCl with AlMe3 at room temperature over a period of 2 days. Treatment of MoH with acetylene affords yellow diamagnetic Mo(η2- CHCH2) plus polyacetylene. The MoCH2R complexes decompose at ~150 °C to yield the alkylidyne complexes, Mo=CR, quantitatively. No change was observed upon heating a toluene solution of MoCH3 to 160 °C for 24 h. However, Mo=CH could be prepared from a mixture of MoCl, 3 equiv of dichloromethane, and a large excess of magnesium powder in THF under argon at 90 °C. Although we have seen no evidence of thermal rearrangement of Mo(η2-CHCH2) to Mo=CCH3, that rearrangement is readily catalyzed by [2,6-LutH]BAr′4. Attempts to prepare Mo-C=CH from [Mo(NH3)]BAr′ 4 and NaC=CH led to formation of a yellow crystalline compound that was shown in an X-ray study to be one in which the acetylide had inserted into an ortho C-H bond in the phenyl ring attached to the amido nitrogen. Orange paramagnetic MoCN can be isolated in good yield from the reaction between [Mo(NH3)]BPh4 and [Bu4N]CN in fluorobenzene. Electrochemical studies in 0.1 M [Bu 4N]BAr′ 4 in PhF at room temperature revealed reversible couples for Mo(C2H4)+/0 and Mo(C2H2)+/0 at -0.42 and -0.94 V, respectively, while Mo(CN) exhibits two redox processes at -0.27 and -1.61 V that we assign to the Mo(CN)+/0 and Mo(CN)0/- redox couples, respectively. Addition of [Cp2Fe]BAr′ 4 to a solution of Mo(η2-C2H2) in C 6D6 produces diamagnetic [Mo(η2-C 2H2)]BAr′ 4, while addition of [Cp 2Fe]BAr'4 to a C6D6 solution of Mo(η2C2H4) led to formation of diamagnetic [Mo(C2H4)]BAr′ 4. Structures of Mo(C 2H4), [Mo(C2H4)]BAr′ 4, Mo(CH2CH3), and Mo(C=CH) were determined through X-ray studies.
- Byrnes, Matthew J.,Dai, Xuliang,Schrock, Richard R.,Hock, Adam S.,Mueller, Peter
-
p. 4437 - 4450
(2008/10/09)
-
- Using Ligand Bite Angles to Control the Hydricity of Palladium Diphosphine Complexes
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A series of [Pd(diphosphine)2](BF4)2 and Pd(diphosphine)2 complexes have been prepared for which the natural bite angle of the diphosphine ligand varies from 78° to 111°. Structural studies have been completed for 7 of the 10 new complexes described. These structural studies indicate that the dihedral angle between the two planes formed by the two phosphorus atoms of the diphosphine ligands and palladium increases by over 50° as the natural bite angle increases for the [Pd(diphosphine)2](BF4)2 complexes. The dihedral angle for the Pd(diphosphine)2 complexes varies less than 10° for the same range of natural bite angles. Equilibrium reactions of the Pd(diphosphine)2 complexes with protonated bases to form the corresponding [HPd(diphosphine)2]+ complexes were used to determine the pKa values of the corresponding hydrides. Cyclic voltammetry studies of the [Pd(diphosphine)2](BF4) 2 complexes were used to determine the half-wave potentials of the Pd(II/I) and Pd(I/0) couples. Thermochemical cycles, half-wave potentials, and measured pKa values were used to determine both the homolytic ([HPd(diphosphine)2]+ → [Pd(diphosphine) 2]+ + H.) and the heterolytic ([HPd(diphosphine)2]+ → [Pd(diphosphine) 2]2+ + H-) bond-dissociation free energies, ΔG°H. and ΔG°H-, respectively. Linear free-energy relationships are observed between pKa and the Pd(I/0) couple and between ΔG°H- and the Pd(II/I) couple. The measured values for ΔG°H. were all 57 kcal/mol, whereas the values of ΔG°H- ranged from 43 kcal/mol for [HPd(depe)2]+ (where depe is bis-(diethylphosphino)ethane) to 70 kcal/mol for [HPd(EtXantphos)2]+ (where EtXantphos is 9,9-dimethyl-4,5-bis(diethylphosphino)xanthene). It is estimated that the natural bite angle of the ligand contributes approximately 20 kcal/mol to the observed difference of 27 kcal/mol for ΔG°H-.
- Raebiger, James W.,Miedaner, Alex,Curtis, Calvin J.,Miller, Susie M.,Anderson, Oren P.,DuBois, Daniel L.
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p. 5502 - 5514
(2007/10/03)
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- Ferrocene-based pincer complexes of palladium: Synthesis, structures, and spectroscopic and electrochemical properties
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Palladium P,C,P pincer complexes based on ferrocene were synthesized for the first time. The reaction of the 1,3-bis((dialkylphosphino)methyl)ferrocenes {1,3-(R2PCH2)2C5H 3}Fe(C5H5 (2a, R = Pri; 2b, R = But) with PdCl2(NCPh)2 in refluxing 2-methoxyethanol leads to the corresponding pincer complexes PdCl[{2,5-(R 2PCH2)2C5H5)] (3a,b). The ferrocene-based binuclear compound 3b reacts with [Cp2Fe]PF 6 to form the ferrocenium-based pincer complex {PdCl[{2,5-(Bu t2PCH2)2C5H 2}Fe(C5H5)]}PF6 (4b), and this is the first example of ferrocene-based phosphine chelate oxidation centered on the iron atom. Treatment of complexes 3a,b with NaBH4 in refluxing ethanol affords the complexes Pd(BH4)[{2,5-(R2-PCH 2)2C5H2}Fe(C5H 5)] (5a, R = Pri; 5b, R = But), containing a BH4- group coordinated to the metal in the rarely occurring unidentate mode. The structures of 3a, b and 5b were confirmed by X-ray analyses. Cyclic voltammetric investigations of complexes 2b and 3a, b are also reported. The structural and spectroscopic features of the palladium ferrocenebased pincer complexes are discussed and compared with those of related compounds.
- Koridze, Avthandil A.,Kuklin, Sergey A.,Sheloumov, Aleksey M.,Dolgushin, Fedor M.,Lagunova, Veronika Yu.,Petukhova, Irina I.,Ezernitskaya, Mariam G.,Peregudov, Alexander S.,Petrovskii, Pavel V.,Vorontsov, Evgenii V.,Baya, Miguel,Poli, Rinaldo
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p. 4585 - 4593
(2008/10/09)
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- Highly active cationic rhodium(I) precatalysts for the ambient temperature ring-opening polymerization of [1]silaferrocenophanes and tetramethyldisilacyclobutane
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The highly active cationic rhodium(I) precatalysts for the ambient temperature ring-opening polymerization (ROP) of [1]silaferrocenophanes and tetramethyldisilacyclobutane were studied. The prolonged exposure of the resulting polyferrocene solution to the catalyst resulted in a dramatic molecular weight decline. It was found that the addition of dmpe effectively arrested the catalytic activity with [Rh(1,5-cod)(dmpe)]PF6.
- Temple, Karen,Dziadek, Sebastian,Manners, Ian
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p. 4377 - 4384
(2008/10/08)
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- Synthesis, structures, and redox properties of mixed-sandwich complexes of cyclopentadienyl and hydrotris(pyrazolyl)borate ligands with first-row transition metals
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The synthesis, structures and redox properties of mixed-sandwich complexes of cyclopentadienyl and hydrotris(pyrazolyl)borate ligands with first-row transition metals were studied. Crystal structure determinations were performed for various complexes. Ana
- Brunker, Tim J.,Cowley, Andrew R.,O'Hare, Dermot
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p. 3123 - 3138
(2008/10/08)
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- Formation of 1,2,4-trisilacyclopentanes by photolysis of FpCH2SiR2SiR2SiR2CH2Fp (Fp = (η5-C5H5)Fe(CO)2)
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Photolysis of FpCH2SiMe2SiMe2SiMe2CH2Fp (1), Fp = [(η5-C5H5)Fe(CO)2], resulted in almost quantitative formation of 1,1,2,2,4,4-hexamethyl-1,2,4-trisilacyclopentane (2) and Fp2. Similar treatment of FpCH2Me2SiMeSiEtSiMe2CH2Fp (6) afforded 1-ethyl-1,2,2,4,4-pentamethyl-1,2,4-trisilacyclopentane (7), indicating that the central silicon of the trisilane remains associated with the silicon-silicon bond of the product. Irradiation of FpCH2-PhMeSiSiMe2SiMe2CH2Fp (11) led to the formation of the two positional isomers (ratio 4:3), 1,1,2,2,4-heptamethyl-4-phenyl-1,2,4-trisilacyclopentane (12a) and 1,1,2,4,4-heptamethyl-2-phenyl-1,2,4-trisilacyclopentane (12b), indicating that either one of the two terminal silicon atoms of the trisilane remains in the Si-Si bond of the product while the other becomes the silicon atom of the product at 4-position. A mechanism for the formation of 1,2,4-trisilacyclopentane is suggested. Irradiation of 11 also produced a small amount the rearranged product FpPhMeSiCH2SiMe2CH2SiMe2Fp (13), whereas photochemical treatment of the tetrasilane analogue, FpCH2SiMe2SiMe2SiMe2SiMe2 CH2Fp (15), resulted in only the high-yield rearrangement product FpMe2SiCH2SiMe2SiMe2CH2Si Me2Fp (17) with an absence of elimination products.
- Zhang, Yongqiang,Pannell, Keith H.
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p. 503 - 510
(2008/10/08)
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