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Prof. Dr. Masaichi Saito Tomoki Akiba Misumi Kaneko Toshiaki Kawamura Dr. Minori Abe Prof. Dr. Masahiko Hada Prof. Dr. Mao Minoura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(50):16946-16953
Plumbacyclopentadienylidenes, in which the lead atoms have divalent states and are coordinated by THF, pyridine and N‐heterocyclic carbene, were synthesized and characterized. The THF‐ and pyridine‐stabilized compounds can be regarded as rare examples of hypervalent 10‐X‐4 species. The equilibrium between the THF adduct and the free plumbacyclopentadienylidene was evidenced by spectroscopic analysis and theoretical calculations. The THF adduct in benzene converted into a plumbylene dimer, where one of the lead centers is coordinated by THF and the other lead atom is coordinated by a divalent lead atom, the dimer gradually decomposing into spiroplumbole. The THF adduct unexpectedly reacted with trifluoroborane and trichlorogallane to afford fluoroborole and chlorogallole, which are the first examples of non‐annulated fluoroborole and gallole, respectively. 相似文献
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Evidence for Extensive Single‐Electron‐Transfer Chemistry in Boryl Anions: Isolation and Reactivity of a Neutral Borole Radical 下载免费PDF全文
Dr. Rüdiger Bertermann Prof. Dr. Holger Braunschweig Dr. Rian D. Dewhurst Dipl.‐Chem. Christian Hörl Dipl.‐Chem. Thomas Kramer Dr. Ivo Krummenacher 《Angewandte Chemie (International ed. in English)》2014,53(21):5453-5457
Despite the synthesis of a boryl anion by Yamashita et al. in 2006, compounds that show boron‐centered nucleophilicity are still rare and sought‐after synthetic goals. A number of such boryl anions have since been prepared, two of which were reported to react with methyl iodide in apparent nucleophilic substitution reactions. One of these, a borolyl anion based on the borole framework, has now been found to display single‐electron‐transfer (SET) reactivity in its reaction with triorganotetrel halides, which was confirmed by the isolation of the first neutral borole‐based radical. The radical was characterized by elemental analysis, single‐crystal X‐ray crystallography, and EPR spectroscopy, and has implications for the understanding of boron‐based nucleophilic behavior and the emergent role of boron radicals in synthesis. This radical reactivity was also exploited in the synthesis of compounds with rare B? Sn and B? Pb bonds, the latter of which was the first isolated and structurally characterized compound with a “noncluster” B? Pb bond. 相似文献
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Inside Back Cover: Evidence for Extensive Single‐Electron‐Transfer Chemistry in Boryl Anions: Isolation and Reactivity of a Neutral Borole Radical (Angew. Chem. Int. Ed. 21/2014) 下载免费PDF全文
Dr. Rüdiger Bertermann Prof. Dr. Holger Braunschweig Dr. Rian D. Dewhurst Dipl.‐Chem. Christian Hörl Dipl.‐Chem. Thomas Kramer Dr. Ivo Krummenacher 《Angewandte Chemie (International ed. in English)》2014,53(21):5473-5473
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Ekkehard Lindner 《Angewandte Chemie (International ed. in English)》1970,9(2):114-123
Reactions of some typical acid halides of carbonic and trithiocarbonic acids and of orthophosphoric and sulfuric acids with Lewis acids and Lewis bases are compared. Acylium, perfluoroacylium, thioacylium, and even sulfonylium ions are obtainable with Lewis acids. It is possible by conductivity measurements and by electronic and above all IR spectroscopic investigations to determine whether the 1:1 adducts of acid halides and Lewis compounds are acylium or sulfonylium salts or donor-acceptor complexes. In the reaction with Lewis bases, the halogen atom in the acid halide is replaced by the electron donor, generally with formation of nonpolar molecular compounds or complexes. 相似文献
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Synthesis,Structure, and Reactivity of Anionic sp2–sp3 Diboron Compounds: Readily Accessible Boryl Nucleophiles 下载免费PDF全文
Sabrina Pietsch Dr. Emily C. Neeve Dr. David C. Apperley Dr. Rüdiger Bertermann Dr. Fanyang Mo Di Qiu Dr. Man Sing Cheung Dr. Li Dang Prof. Dr. Jianbo Wang Prof. Dr. Udo Radius Prof. Dr. Zhenyang Lin Dr. Christian Kleeberg Prof. Dr. Todd B. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19):7082-7098
Lewis base adducts of tetra‐alkoxy diboron compounds, in particular bis(pinacolato)diboron (B2pin2), have been proposed as the active source of nucleophilic boryl species in metal‐free borylation reactions. We report the isolation and detailed structural characterization (by solid‐state and solution NMR spectroscopy and X‐ray crystallography) of a series of anionic adducts of B2pin2 with hard Lewis bases, such as alkoxides and fluoride. The study was extended to alternative Lewis bases, such as acetate, and other diboron reagents. The B(sp2)–B(sp3) adducts exhibit two distinct boron environments in the solid‐state and solution NMR spectra, except for [(4‐tBuC6H4O)B2pin2]?, which shows rapid site exchange in solution. DFT calculations were performed to analyze the stability of the adducts with respect to dissociation. Stoichiometric reaction of the isolated adducts with two representative series of organic electrophiles—namely, aryl halides and diazonium salts—demonstrate the relative reactivities of the anionic diboron compounds as nucleophilic boryl anion sources. 相似文献
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Frontispiece: Synthesis,Structure, and Reactivity of Anionic sp2–sp3 Diboron Compounds: Readily Accessible Boryl Nucleophiles 下载免费PDF全文
Sabrina Pietsch Dr. Emily C. Neeve Dr. David C. Apperley Dr. Rüdiger Bertermann Dr. Fanyang Mo Di Qiu Dr. Man Sing Cheung Dr. Li Dang Prof. Dr. Jianbo Wang Prof. Dr. Udo Radius Prof. Dr. Zhenyang Lin Dr. Christian Kleeberg Prof. Dr. Todd B. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19)
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Santhosh Kumar K. S. Dr. Yugang Li Dr. Yves Gnanou Dr. Ulrich Baisch Dr. Yohan Champouret Dr. Rinaldo Poli Prof. Kiyoshi C. D. Robson W. Stephen McNeil Prof. 《化学:亚洲杂志》2009,4(8):1257-1265
Complexes Co[OC(Ph)CHC(Me)NAr]2 [Ar=Ph, 1 ; o,o′‐C6H3Me2 (Xyl), 2 ; p‐C6H4CF3, 3 ] are tested in the polymerization of vinyl acetate (VAc) initiated by V‐70 (0.8 equiv) at 30 °C. Polymerization occurs without any notable induction time yielding PVAc with relatively low polydispersity, but with higher than expected Mn values, which indicates inefficient trapping processes. The apparent polymerization rate constant varies in the order 2 > 1 > 3 . Controlled polymer growth is also observed when the polymerization is conducted in the presence of a much higher V‐70/ 1 ratio, demonstrating that this system can also function as a transfer agent in a degenerative transfer process. Competition between chain growth and catalyzed chain transfer (CCT) is also observed, the latter prevailing at higher temperatures. Comparison of these results with previous reports on bis(β‐diketonato) complexes allows a separate assessment of ligand electronic and steric effects in the ability to control polymerization. 相似文献
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Tsuyoshi Taniguchi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(19):e202104333
The present review focuses on recent examples of tetracoordinate boryl groups greatly influencing reactions in organic synthesis. Electron-rich tetracoordinate boryl groups stabilize or activate reactive intermediates such as cations, radicals and π-conjugation systems, and interaction of the intermediates with carbon-boron or heteroatom-boron bonds is the origin of such substituent effects. Unique substituent effects of tetracoordinate boryl groups often promote desired reactions and affect results of reactions such as yield and selectivity of products. 相似文献
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On the Synthesis,Characterization and Reactivity of N‐Heteroaryl–Boryl Radicals,a New Radical Class Based on Five‐Membered Ring Ligands 下载免费PDF全文
Dr. Mohamad‐Ali Tehfe Dr. Stéphane Schweizer Dr. Anne‐Caroline Chany Dr. Cédric Ysacco Dr. Jean‐Louis Clément Dr. Didier Gigmes Dr. Fabrice Morlet‐Savary Prof. Jean‐Pierre Fouassier Dr. Markus Neuburger Dr. Théophile Tschamber Dr. Nicolas Blanchard Prof. Jacques Lalevée 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(17):5054-5063
The synthesis and physical characterization of a new class of N‐heterocycle–boryl radicals is presented, based on five membered ring ligands with a N(sp2) complexation site. These pyrazole–boranes and pyrazaboles exhibit a low bond dissociation energy (BDE; B?H) and accordingly excellent hydrogen transfer properties. Most importantly, a high modulation of the BDE(B?H) by the fine tuning of the N‐heterocyclic ligand was obtained in this series and could be correlated with the spin density on the boron atom of the corresponding radical. The reactivity of the latter for small molecule chemistry has been studied through the determination of several reaction rate constants corresponding to addition to alkenes and alkynes, addition to O2, oxidation by iodonium salts and halogen abstraction from alkyl halides. Two selected applications of N‐heterocycle–boryl radicals are also proposed herein, for radical polymerization and for radical dehalogenation reactions. 相似文献
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A Unified Treatment of the Relationship Between Ligand Substituents and Spin State in a Family of Iron(II) Complexes 下载免费PDF全文
Dr. Laurence J. Kershaw Cook Dr. Rafal Kulmaczewski Dr. Rufeida Mohammed Stephen Dudley Simon A. Barrett Dr. Marc A. Little Prof. Robert J. Deeth Prof. Malcolm A. Halcrow 《Angewandte Chemie (International ed. in English)》2016,55(13):4327-4331
The influence of ligands on the spin state of a metal ion is of central importance for bioinorganic chemistry, and the production of base‐metal catalysts for synthesis applications. Complexes derived from [Fe(bpp)2]2+ (bpp=2,6‐di{pyrazol‐1‐yl}pyridine) can be high‐spin, low‐spin, or spin‐crossover (SCO) active depending on the ligand substituents. Plots of the SCO midpoint temperature (T ) in solution vs. the relevant Hammett parameter show that the low‐spin state of the complex is stabilized by electron‐withdrawing pyridyl (“X”) substituents, but also by electron‐donating pyrazolyl (“Y”) substituents. Moreover, when a subset of complexes with halogeno X or Y substituents is considered, the two sets of compounds instead show identical trends of a small reduction in T for increasing substituent electronegativity. DFT calculations reproduce these disparate trends, which arise from competing influences of pyridyl and pyrazolyl ligand substituents on Fe‐L σ and π bonding. 相似文献
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Influence of Electronic Effects on the Reactivity of Triazolylidene‐Boryl Radicals: Consequences for the use of N‐Heterocyclic Carbene Boranes in Organic and Polymer Synthesis 下载免费PDF全文
Sofia Telitel Anne‐Laure Vallet Darrin M. Flanigan Dr. Bernadette Graff Dr. Fabrice Morlet‐Savary Prof. Tomislav Rovis Prof. Jacques Lalevée Dr. Emmanuel Lacôte 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13772-13777
A small library of triazolylidene‐boranes that differ only in the nature of the aryl group on the external nitrogen atom was prepared. Their reactivity as hydrogen‐atom donors, as well as that of the corresponding N‐heterocyclic carbene (NHC)‐boryl radicals toward methyl acrylate and oxygen, was investigated by laser flash photolysis, molecular orbital calculations, and ESR spin‐trapping experiments, and benchmarked relative to the already known dimethyltriazolylidene‐borane. The new NHC‐boranes were also used as co‐initiators for the Type I photopolymerization of acrylates. This allowed a structure–reactivity relationship with regard to the substitution pattern of the NHC to be established and the role of electronic effects in the reactivity of NHC‐boryl radicals to be probed. Although their rate of addition to methyl acrylate depends on their electronegativity, the radicals are all nucleophilic and good initiators for photopolymerization reactions. 相似文献
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On the Reactivity of Tetrakis(trifluoromethyl)cyclopentadienone towards Carbon‐Based Lewis Bases 下载免费PDF全文
Sigrid Holle Dr. Daniel Escudero Dr. Blanca Inés Jörg Rust Prof. Walter Thiel Dr. Manuel Alcarazo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):2744-2749
The reactivitiy of tetrakis(trifluoromethyl)cyclopentadienone towards different C‐based Lewis bases, such as N‐heterocyclic carbenes (NHC), ylides and isonitriles, are reported. While sterically not hindered carbenes were found to yield kinetic adducts by regiospecific nucleophilic attack at the position adjacent to the carbonyl group of the ketone, bulkier nucleophiles afforded the thermodynamically more stable O‐bridged zwitterions. Interestingly, isonitriles were found to dimerize and trimerize under the same reaction conditions, forming bicyclic products that evolve differently depending on the nature of the substituents. 相似文献
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Vermoortele F Vandichel M Van de Voorde B Ameloot R Waroquier M Van Speybroeck V De Vos DE 《Angewandte Chemie (International ed. in English)》2012,51(20):4887-4890
Functionalized linkers can greatly increase the activity of metal-organic framework (MOF) catalysts with coordinatively unsaturated sites. A clear linear free-energy relationship (LFER) was found between Hammett σ(m) values of the linker substituents X and the rate k(X) of a carbonyl-ene reaction. This is the first LFER ever observed for MOF catalysts. A 56-fold increase in rate was found when the substituent is a nitro group. 相似文献
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This work presents an experimental and theoretical study to address the chemical reactivity of series of nitroxide radicals. For that purpose two physicochemical properties: the half-wave potential and the hyperfine coupling constants of the nitrogen nuclei, were analyzed. Experimental values are compared with electronic structure calculations at the BHandHLYP/6-311++G(2d,2p) level. E1/2 values were in good agreement with the adiabatic ionization potential when including the solvent effects by the Cramer and Truhlar Solvation Model. Preeliminar experimental electron spin deslocalization studies suggest that structural hindrance plays an important role in their deslocatization mechanism. 相似文献