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Ken'ichi Takeuchi - One of the best experts on this subject based on the ideXlab platform.
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Orbital Interactions and Solvent Effects Determining the Stability of Condensed Cyclopentadienides in Solution.
Journal of Organic Chemistry, 1999Co-Authors: Kazunari Yoshizawa, Kazuyuki Yahara, Aya Taniguchi, Tokio Yamabe, Tomomi Kinoshita, Ken'ichi TakeuchiAbstract:The structure and the stability of various Cyclopentadienides, which involve 6π, 10π, 14π, and 22π electrons, are investigated from computations at various levels of theory as well as from orbital interaction analyses. The reason that some of the Cyclopentadienides are stabilized and others are destabilized by the introduction of aromatic rings is discussed in terms of absolute hardness and orbital interaction. Cyclopentadienide, a special 6π-electron system, has the largest value of absolute hardness among the condensed Cyclopentadienides investigated; thus this carbanion resists both oxidation and reduction most strongly. The absolute hardness decreases when aromatic rings are introduced to Cyclopentadienide to form condensed Cyclopentadienides, depending on the way they are connected. Computed values of the ionization potential and oxidation potentials measured in solution have a linear correlation within isomers of the same size, but are not in agreement for different sets of isomers. Solvent effects ...
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hydrocarbon anions with high stability part 2 structure and stability of Cyclopentadienide ions with condensed aromatic rings
Bulletin of the Chemical Society of Japan, 1998Co-Authors: Tomomi Kinoshita, Kazunari Yoshizawa, Ken'ichi Takeuchi, Masaya Fujita, Hideyuki Kaneko, Tokio YamabeAbstract:The ionization-potential and oxidation-potential values have been examined as stability parameters in the gas and solution phase, respectively, for Cyclopentadienide ions with from one to four condensed aromatic rings. They indicate that, without solvation effects, the condensed aromatic rings intrinsically stabilize the Cyclopentadienide ion in solution as well as in the gas phase, and that an apparent destabilization effect by the aromatic rings in solution is most probably ascribed to a decrease in the stabilizing solvation effects due to charge delocalization on the carbanions. Theoretical investigations from governing orbital interactions using the frontier orbital theory demonstrate that the essential stability of the Cyclopentadienide ions is dependent on the structure, itself.
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the effects of t butyl substituents on the thermodynamic stability of the Cyclopentadienide ion
Journal of Organometallic Chemistry, 1994Co-Authors: Tomomi Kinoshita, Naoshi Murata, Ryohei Fujita, Yoshitaka Yanagi, Ken'ichi TakeuchiAbstract:Abstract The effects have been quantified of t-butyl substituents on the thermodynamic stability of Cyclopentadienide ions with no, one, two, and three t-butyl groups, 1 − , 2 − , 3 − and 4 − , respectively. The stability estimated from oxidation potential values decreases in the order 1 − (+ 0.04 V) > 2 − (− 0.16 V) > 3 − (− 0.28 V) > 4 − (−0.45 V). The stability evaluated from p K a values decreases in the same sequence ( 1H : 18.2, 2H : 19.9, 3H : 21.9, and 4H : 25.0 in DMSO). The t-butyl substituent reduces the thermodynamic stability of Cyclopentadienide ion in step with increasing number of substituents and this is most probably due to a decrease in solvation and an increase in inductive effect in the carbanion.
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poly linked Cyclopentadienide ions ii synthesis and properties of the tetracyclopentadienylmethane tetraanion
Journal of Organometallic Chemistry, 1993Co-Authors: Tomomi Kinoshita, Shigeo Tsuji, Tadashi Otake, Ken'ichi TakeuchiAbstract:The title tetraanion (1d) has been synthesized via ferrocenyl derivatives. Dynamic 1H NMR spectroscopy indicates the most stable conformation of 1d and the barrier to internal rotation of Cyclopentadienide rings.
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poly linked Cyclopentadienide ions 1 synthesis and properties of tris cyclopentadienyl methane trianion
Tetrahedron Letters, 1990Co-Authors: Tomomi Kinoshita, Ken'ichi Takeuchi, Shigeo Tsuji, Shunji Tatsumi, Yukihito Zanka, Yasuhiko Takamuki, Mitsuo Fukumasa, Kunio OkamotoAbstract:Abstract Tris(cyclopentadienyl)methane trianion has been synthesized via triferrocenylmethyl derivatives. The dynamic 1H NMR spectroscopy indicates the barrier to internal rotation of cyclopentadienido rings.
Olaf Walter - One of the best experts on this subject based on the ideXlab platform.
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solid state structure of tris Cyclopentadienide uranium iii and plutonium iii
Chemistry: A European Journal, 2018Co-Authors: Christos Apostolidis, Michal S Dutkiewicz, Attila Kovacs, Olaf WalterAbstract:: The organometallic tris-Cyclopentadienide actinide(III) (AnCp3 ) complexes were first reported about 50 years ago. However, up until now, only the NpCp3 solid state structure has been studied. Here we report on the solid state structures of UCp3 and PuCp3 which are isostructural to the Np analogue. The structural models are supported by theoretical calculations and compared to their lanthanide analogues. The observed trends in changes of bond lengths might be indicator for an increased covalency in the bonding in the tris-Cyclopentadienide actinide(III) complexes (AnCp3 ) compared to their lanthanide homologues.
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reduction chemistry of neptunium Cyclopentadienide complexes from structure to understanding
Chemical Science, 2017Co-Authors: Michal S Dutkiewicz, Christos Apostolidis, Olaf Walter, Polly L ArnoldAbstract:Neptunium complexes in the formal oxidation states II, III, and IV supported by cyclopentadienyl ligands are explored, and significant differences between Np and U highlighted as a result. A series of neptunium(III) cyclopentadienyl (Cp) complexes [Np(Cp)3], its bis-acetonitrile adduct [Np(Cp)3(NCMe)2], and its KCp adduct K[Np(Cp)4] and [Np(Cp′)3] (Cp′ = C5H4SiMe3) have been made and characterised providing the first single crystal X-ray analyses of NpIII Cp complexes. In all NpCp3 derivatives there are three Cp rings in η5-coordination around the NpIII centre; additionally in [Np(Cp)3] and K[Np(Cp)4] one Cp ring establishes a μ-η1-interaction to one C atom of a neighbouring Np(Cp)3 unit. The solid state structure of K[Np(Cp)4] is unique in containing two different types of metal–Cp coordination geometries in the same crystal. NpIII(Cp)4 units are found exhibiting four units of η5-coordinated Cp rings like in the known complex [NpIV(Cp)4], the structure of which is now reported. A detailed comparison of the structures gives evidence for the change of ionic radii of ca. −8 pm associated with change in oxidation state between NpIII and NpIV. The rich redox chemistry associated with the syntheses is augmented by the reduction of [Np(Cp′)3] by KC8 in the presence of 2.2.2-cryptand to afford a neptunium(II) complex that is thermally unstable above −10 °C like the UII and ThII complexes K(2.2.2-cryptand)[Th/U(Cp′)3]. Together, these spontaneous and controlled redox reactions of organo-neptunium complexes, along with information from structural characterisation, show the relevance of organometallic Np chemistry to understanding fundamental structure and bonding in the minor actinides.
Tomomi Kinoshita - One of the best experts on this subject based on the ideXlab platform.
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Orbital Interactions and Solvent Effects Determining the Stability of Condensed Cyclopentadienides in Solution.
Journal of Organic Chemistry, 1999Co-Authors: Kazunari Yoshizawa, Kazuyuki Yahara, Aya Taniguchi, Tokio Yamabe, Tomomi Kinoshita, Ken'ichi TakeuchiAbstract:The structure and the stability of various Cyclopentadienides, which involve 6π, 10π, 14π, and 22π electrons, are investigated from computations at various levels of theory as well as from orbital interaction analyses. The reason that some of the Cyclopentadienides are stabilized and others are destabilized by the introduction of aromatic rings is discussed in terms of absolute hardness and orbital interaction. Cyclopentadienide, a special 6π-electron system, has the largest value of absolute hardness among the condensed Cyclopentadienides investigated; thus this carbanion resists both oxidation and reduction most strongly. The absolute hardness decreases when aromatic rings are introduced to Cyclopentadienide to form condensed Cyclopentadienides, depending on the way they are connected. Computed values of the ionization potential and oxidation potentials measured in solution have a linear correlation within isomers of the same size, but are not in agreement for different sets of isomers. Solvent effects ...
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hydrocarbon anions with high stability part 2 structure and stability of Cyclopentadienide ions with condensed aromatic rings
Bulletin of the Chemical Society of Japan, 1998Co-Authors: Tomomi Kinoshita, Kazunari Yoshizawa, Ken'ichi Takeuchi, Masaya Fujita, Hideyuki Kaneko, Tokio YamabeAbstract:The ionization-potential and oxidation-potential values have been examined as stability parameters in the gas and solution phase, respectively, for Cyclopentadienide ions with from one to four condensed aromatic rings. They indicate that, without solvation effects, the condensed aromatic rings intrinsically stabilize the Cyclopentadienide ion in solution as well as in the gas phase, and that an apparent destabilization effect by the aromatic rings in solution is most probably ascribed to a decrease in the stabilizing solvation effects due to charge delocalization on the carbanions. Theoretical investigations from governing orbital interactions using the frontier orbital theory demonstrate that the essential stability of the Cyclopentadienide ions is dependent on the structure, itself.
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the effects of t butyl substituents on the thermodynamic stability of the Cyclopentadienide ion
Journal of Organometallic Chemistry, 1994Co-Authors: Tomomi Kinoshita, Naoshi Murata, Ryohei Fujita, Yoshitaka Yanagi, Ken'ichi TakeuchiAbstract:Abstract The effects have been quantified of t-butyl substituents on the thermodynamic stability of Cyclopentadienide ions with no, one, two, and three t-butyl groups, 1 − , 2 − , 3 − and 4 − , respectively. The stability estimated from oxidation potential values decreases in the order 1 − (+ 0.04 V) > 2 − (− 0.16 V) > 3 − (− 0.28 V) > 4 − (−0.45 V). The stability evaluated from p K a values decreases in the same sequence ( 1H : 18.2, 2H : 19.9, 3H : 21.9, and 4H : 25.0 in DMSO). The t-butyl substituent reduces the thermodynamic stability of Cyclopentadienide ion in step with increasing number of substituents and this is most probably due to a decrease in solvation and an increase in inductive effect in the carbanion.
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poly linked Cyclopentadienide ions ii synthesis and properties of the tetracyclopentadienylmethane tetraanion
Journal of Organometallic Chemistry, 1993Co-Authors: Tomomi Kinoshita, Shigeo Tsuji, Tadashi Otake, Ken'ichi TakeuchiAbstract:The title tetraanion (1d) has been synthesized via ferrocenyl derivatives. Dynamic 1H NMR spectroscopy indicates the most stable conformation of 1d and the barrier to internal rotation of Cyclopentadienide rings.
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poly linked Cyclopentadienide ions 1 synthesis and properties of tris cyclopentadienyl methane trianion
Tetrahedron Letters, 1990Co-Authors: Tomomi Kinoshita, Ken'ichi Takeuchi, Shigeo Tsuji, Shunji Tatsumi, Yukihito Zanka, Yasuhiko Takamuki, Mitsuo Fukumasa, Kunio OkamotoAbstract:Abstract Tris(cyclopentadienyl)methane trianion has been synthesized via triferrocenylmethyl derivatives. The dynamic 1H NMR spectroscopy indicates the barrier to internal rotation of cyclopentadienido rings.
Julian F S Vaughan - One of the best experts on this subject based on the ideXlab platform.
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reactions involving fluoride ion part 41 1 2 synthesis of hexakis trifluoromethyl cyclopentadiene and derived Cyclopentadienide salts
Journal of The Chemical Society-perkin Transactions 1, 1997Co-Authors: Richard D Chambers, Julian F S Vaughan, William K Gray, Stewart R Korn, Maurice Medebielle, Andrei S Batsanov, Christian W Lehmann, Judith A K HowardAbstract:An efficient synthesis of hexakis(trifluoromethyl)cyclopentadiene 4, which shows a remarkably low reduction potential, is described. Various donors promote one-electron transfer to 4, leading to corresponding salts of pentakis(trifluoromethyl)Cyclopentadienide 5. A novel approach to the synthesis of metal derivatives involves heating, or photolysis, of 4 directly with metals (including Cu, Ni, Fe and Co), leading to the corresponding ionic salts. X-Ray structural analysis was difficult because of rotation of trifluoromethyl groups in these salts, but structural data on 20, 24 and 30 has been obtained that reveals interesting conformations and stacking of the ions.
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direct syntheses of pentakis trifluoromethyl Cyclopentadienide salts and related systems
Canadian Journal of Chemistry, 1996Co-Authors: Richard D Chambers, Alex J Roche, Julian F S VaughanAbstract:The well-established synthesis of heptafluorobut-2-ene 2 from hexachlorobutadiene 1 and potassium fluoride has been further investigated, and novel dienes 3 and a triene 4 have been observed. Remarkably, the potassium salt of pentakis(trifluoromethyl)Cyclopentadienide 7 has been isolated from this system. Salt 7 has also been obtained directly from 2. Cyclopentadiene 6 has been isolated from salt 7 by distillation from sulphuric acid. Bi-and tri-cyclic analogues of 7 have also been obtained, i.e., 9 and 10, by reaction of 2 with perfluorocyclopentene. Key words: heptafluorobut-2-ene, pentakis(trifluoromethyl)Cyclopentadienide, 5H-pentakis(trifluoromethyl)cyclopentadiene.
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direct syntheses of pentakis trifluoromethyl Cyclopentadienide salts and related dienes
Journal of The Chemical Society Chemical Communications, 1995Co-Authors: Richard D Chambers, Alex J Roche, S J Mullins, Julian F S VaughanAbstract:Direct routes for the synthesis of pentakis(trifluoromethyl)Cyclopentadienide salts, hexakis(trifluoromethyl)cyclopentadiene and 5H pentakis(trifluoromethyl)cyclopentadiene are described.
Bernard Sillion - One of the best experts on this subject based on the ideXlab platform.
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reaction of Cyclopentadienide carbanion with α α dibromometaxylene an unexpected example of polyanionic substitution
Polymer, 2000Co-Authors: Ben H Romdhane, M.r. Chaabouni, P. Mison, Marieflorence Grenierloustalot, F Delolme, Bernard SillionAbstract:Abstract The reaction of α,α′-dibromometaxylene (DBMX) with sodium Cyclopentadienide (CpNa) gives several oligomers, which were characterized by Size Exclusion Chromatography (SEC) and Liquid Secondary Ion Mass Spectroscopy (LSIMS). The obtained oligomers came from two competitive mechanisms after an anionic substitution of the DBMX by CpNa. The first was based on the proton transfer between the monosubstituted DBMX and CpNa giving a transcient monobrominate carbanion which is the propagating species of a polyanionic substitution. The second one is a classical Diels–Alder reaction between two oligomers containing substituted cyclopentadienes (CPDs) and also between an oligomer and the CPD formed in situ by hydrogen transfer.
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A Model study for Diels-Alder reaction of biscyclopentadienyl monomer with bismaleimides. Benzylcyclopentadiene: synthesis, characterization and Diels-Alder reaction with N-(4-benzoyl)-phenylmaleimide.
Polymer, 2000Co-Authors: H. Ben Rhomdhane, M.r. Chaabouni, Marie-florence Grenier-loustalot, Frédéric Delolme, P. Mison, Bernard SillionAbstract:Reaction between benzylbromide and sodium Cyclopentadienide leads to a mixture of dienes. These can be identified by several techniques such as size exclusion chromatography, mass spectroscopy (MS) and high performance liquid chromatography/MS coupling. Their structure is confirmed by analysis of adducts obtained after reaction of N-(4-benzoyl)-phenylmaleimide with these dienes.
