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1.
Xu BH Mömming CM Fröhlich R Kehr G Erker G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(6):1826-1830
The frustrated Lewis pair Mes(2)PCH(2)CH(2)B(C(6)F(5))(2) reacts readily with 6-dimethylamino-6-methylfulvene at room temperature to yield the trans-1-[B(C(6)F(5))(2)]-2-[CH(2)CH(2)PMes(2)] disubstituted fulvene derivative 9 that features an internal N-B contact. Thermolysis (80 °C in toluene) results in a complete isomerization to the respective 1-[B(C(6)F(5))(2)]-3-[CH(2)CH(2)PMes(2)] isomer 10. Both compounds were characterized by using X-ray diffraction. A reaction scheme is formulated to rationalize the specific formation of these compounds, involving a retro-hydroboration/hydroboration sequence. The reaction of the 6-dimethylaminofulvene with HB(C(6)F(5))(2) yielded the corresponding parent compound 13 that was also characterized by X-ray diffraction. 相似文献
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The steric and electronic effects exerted by the substituents R/R′ on the heterolytic H2‐splitting by phosphine‐boranes R3B/PR′3 [R = C6F5 ( 1 ), Ph ( 2 ); R′ = C6H2Me3 ( a ), tBu ( b ), Ph ( c ), C6F5 ( d ), Me ( e ), H ( f )] have been studied by performing quantum mechanical density functional theory and RI‐MP2 calculations. Energy decomposition analyses based on the block‐localized wavefunction method show that the nature of the interaction between R3B and PR′3 is strongly dependent on the B? P distance. With short B? P distances (~2.1 Å), the strength of Lewis pairs results from the balance among various energy terms, and both strong and weak dative bonds can be found in this group. However, at long B? P distances (>4.0 Å), the correlation and dispersion energy (ΔEcorr) dominates. In other words, the van der Waals (vdW) interaction rules these weakly bound complexes. No ion‐pair structures of 1f and 2c – 2f can be located as they instantly converge to vdW complexes R3B···H2···PR′3. We thus propose a model, which predicts that when the sum (Ehp) of the hydride affinity (HA) of BR3 and the proton affinity (PA) of PR′3 is higher than 340.0 kcal/mol, the ion‐pair [R3BH?][HPR′] can be observed, whereas with Ehp below this value, the ion pair would instantly undergo the combination of proton and hydride with the release of H2. The overall reaction energies ( 1a – 1e and 2a – 2b ) can be best described by a fitting equation with HA(BR3), PA(PR′3), and the binding energy ΔEb(BR3/PR′3) as predictor variables: ΔER([R3BH?][HPR′]) = ?0.779HA(BR3) ? 0.695PA(PR′3) ? 1.331 ΔE (BR3/PR′3) + 245.3 kcal/mol. The fitting equation provides quantitative insights into the steric and electronic effects on the thermodynamic aspects of the heterolytic H2‐splitting reactions. The electronic effects are reflected by HA(BR3) and PA(PR′3), and ΔEb can be significantly influenced by the steric overcrowding. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
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Sina Schwendemann Shunsuke Oishi Prof. Dr. Susumu Saito Dr. Roland Fröhlich Dr. Gerald Kehr Prof. Dr. Gerhard Erker 《化学:亚洲杂志》2013,8(1):212-217
D ‐(+)‐Camphor forms the enamine 2 with piperidine. Compound 2 adds HB(C6F5)2 at the enamine carbon atom C3 to form a Lewis acid/Lewis base adduct (exo‐/endo‐isomers of 3 ). Exposure of 3 to dihydrogen (2.5 bar, room temperature) leads to heterolytic splitting of H2 to form the H+/H? addition products ( 4 , two diastereoisomers) of the “invisible” frustrated Lewis pairs ( 5 , two diastereoisomers) that were apparently generated in situ by enamine hydroboration under equilibrium conditions. 相似文献
4.
Hydroboration as an Efficient Tool for the Preparation of Electronically and Structurally Diverse N→B‐Heterocycles
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Markus Grandl Thomas Kaese Anke Krautsieder Dr. Yu Sun Dr. Frank Pammer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14373-14382
Ladder‐type organoboranes featuring intramolecular N→B coordination have been prepared through hydroboration of a 2‐(ortho‐styryl)pyridine ( PhPy ) with a series of hydroboranes, including 9H‐9‐borabicyclo[3.3.1]nonyl (9H‐BBN), BH3 ? THF, HBCl2 ? SMe2, HB(C6F5)2, and a 9H‐9‐borafluorene derivative. The hydroboration reaction results in highly regioselective borylation under mild conditions and gives the products in good to excellent yields. The molecular structure and electronic properties of the obtained boranes have been experimentally investigated in detail, and complemented with DFT calculations to further elucidate the origin of differences in optical and electronic properties. The electron affinity of the conjugated system can be controlled through variation of the borane, while the optical properties are likewise directly linked to the type and molecular structure of the substituents on boron. The broad substrate range shows that this preparative approach is widely applicable to introduce chemically diverse boryl groups into conjugated systems. 相似文献
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《Angewandte Chemie (International ed. in English)》2017,56(1):333-337
Intramolecular germylene, stannylene, and plumbylene Lewis pairs were reacted with hexanal and yielded the cyclic addition products only with the germanium and tin reagents. In further reactivity studies, the hydroboration of aldehydes and ketones catalyzed by intramolecular germylene, stannylene, and plumbylene Lewis pairs was studied. In the case of the cyclic germylene Lewis pair, the product of the oxidative addition of pinacolborane at the germylene moiety was observed. According to stoichiometric as well as catalytic experiments, the intramolecular germylene Lewis pair acts as a catalyst in the hydroboration of aldehydes and ketones. The homologous stannylene Lewis pair forms a reactive tin hydride during the catalysis, which can also act as a catalyst in this transformation. 相似文献
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Werner Uhl Frank Hengesbach Jennifer Isermann Meisam Soleimani Lina Schürmann Alexander Hepp Marcus Layh 《无机化学与普通化学杂志》2019,645(20):1205-1214
Hydrogallation of Me3Si–C≡C–NR'2 with R2Ga–H (R = tBu, CH2tBu, iBu) yielded Ga/N‐based active Lewis pairs, R2Ga–C(SiMe3)=C(H)–NR'2 ( 7 ). The Ga and N atoms adopt cis‐positions at the C=C bonds and show weak Ga–N interactions. tBu2GaH and Me3Si–C≡C–N(C2H4)2NMe afforded under exposure of daylight the trifunctional digallium(II) compound [MeN(C2H4)2N](H)C=C(SiMe3)Ga(tBu)–Ga(tBu)C(SiMe3)=C(H)[N(C2H4)2NMe] ( 8 ), which results from elimination of isobutene and H2 and Ga–Ga bond formation. 8 was selectively obtained from the ynamine and [tBu(H)Ga–Ga(H)tBu]2[HGatBu2]2. 7a (R = tBu; NR'2 = 2,6‐Me2NC5H8) and H8C4N–C≡N afforded the adduct tBu2Ga‐C(SiMe3)=C(H)(2,6‐Me2NC5H8) · N≡C–NC4H8 ( 11 ) with the nitrile bound to gallium. The analogous ALP with harder Al atoms yielded an adduct of the nitrile dimer or oligomers of the nitrile at room temperature. The reaction of 7a with Ph–N=C=O led to the insertion of two NCO groups into the Ga–Cvinyl bond to yield a GaOCNCN heterocycle with Ga bound to O and N atoms ( 12 ). 相似文献
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《Angewandte Chemie (International ed. in English)》2017,56(11):3094-3097
An Al/P‐based frustrated Lewis pair (FLP) reacted with PhMgCl by an unexpected transmetalation and formation of a phosphinylvinyl Grignard reagent. This compound is well suited for the transfer of the basic FLP component to other Lewis acidic metal atoms and allowed the generation of a Ga/P and an In/P2 FLP. The Ga FLP showed a behavior different to that of the corresponding Al FLP, the In FLP allowed the chelating coordination of an Au atom by Au−Cl bond activation. 相似文献
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Boron Lewis Acid‐Catalyzed Hydroboration of Alkenes with Pinacolborane: BArF3 Does What B(C6F5)3 Cannot Do!
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Dr. Qin Yin Dr. Hendrik F. T. Klare Prof. Dr. Martin Oestreich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(39):13840-13844
The transition‐metal‐free hydroboration of various alkenes with pinacolborane (HBpin) initiated by tris[3,5‐bis(trifluoromethyl)phenyl]borane (BArF3) is reported. The choice of the boron Lewis acid is crucial as the more prominent boron Lewis acid tris(pentafluorophenyl)borane (B(C6F5)3) is reluctant to react. Unlike B(C6F5)3, BArF3 is found to engage in substituent redistribution with HBpin, resulting in the formation of ArFBpin and the electron‐deficient diboranes [H2BArF]2 and [(ArF)(H)B(μ‐H)2BArF2]. These in situ‐generated hydroboranes undergo regioselective hydroboration of styrene derivatives as well as aliphatic alkenes with cis diastereoselectivity. Another ligand metathesis of these adducts with HBpin subsequently affords the corresponding HBpin‐derived anti‐Markovnikov adducts. The reactive hydroboranes are regenerated in this step, thereby closing the catalytic cycle. 相似文献
11.
Cooperative Lewis Pairs Based on Late Transition Metals: Activation of Small Molecules by Platinum(0) and B(C6F5)3
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Sebastian J. K. Forrest Jamie Clifton Dr. Natalie Fey Prof. Paul G. Pringle Dr. Hazel A. Sparkes Prof. Duncan F. Wass 《Angewandte Chemie (International ed. in English)》2015,54(7):2223-2227
A Lewis basic platinum(0)–CO complex supported by a diphosphine ligand and B(C6F5)3 act cooperatively, in a manner reminiscent of a frustrated Lewis pair, to activate small molecules such as hydrogen, CO2, and ethene. This cooperative Lewis pair facilitates the coupling of CO and ethene in a new way. 相似文献
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Functionalization of Intramolecular Frustrated Lewis Pairs by 1,1‐Carboboration with Conjugated Enynes
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Dr. Andreas Feldmann Dr. Gerald Kehr Dr. Constantin G. Daniliuc Dr. Christian Mück‐Lichtenfeld Prof. Dr. Gerhard Erker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(35):12456-12464
The vicinal P/B frustrated Lewis pair (FLP) Mes2PCH2CH2B(C6F5)2 undergoes 1,1‐carboboration reactions with the Me3Si‐substituted enynes to give ring‐enlarged functionalized C3‐bridged P/B FLPs. These serve as active FLPs in the activation of dihydrogen to give the respective zwitterionic [P]H+/[B]H? products. One such product shows activity as a metal‐free catalyst for the hydrogenation of enamines or a bulky imine. The ring‐enlarged FLPs contain dienylborane functionalities that undergo “bora‐Nazarov”‐type ring‐closing rearrangements upon photolysis. A DFT study had shown that the dienylborane cyclization of such systems itself is endothermic, but a subsequent C6F5 migration is very favorable. Furthermore, substituted 2,5‐dihydroborole products are derived from cyclization and C6F5 migration from the photolysis reaction. In the case of the six‐membered annulation product, a subsequent stereoisomerization reaction takes place and the resultant compound undergoes a P/B FLP 1,2‐addition reaction with a terminal alkyne with rearrangement. 相似文献
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Aurélien Adenot Dr. Niklas von Wolff Dr. Guillaume Lefèvre Dr. Jean-Claude Berthet Dr. Pierre Thuéry Dr. Thibault Cantat 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(34):8118-8126
The guanidine 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and the substituted derivatives [TBD–SiR2]+ and TBD–BR2 reacted with SO2 to give different FLP–SO2 adducts. Molecular structures, elucidated by X-ray diffraction, showed some structural similarities with the analogous CO2 adducts. Thermodynamic stabilities were both experimentally evidenced and computed through DFT calculations. The underlying parameters governing the relative stabilities of the different SO2 and CO2 adducts were discussed from a theoretical standpoint, with a focus on the influence of the Lewis acidic moiety. 相似文献
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Dr. Ewan R. Clark Alessandro Del Grosso Dr. Michael J. Ingleson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(7):2462-2466
A range of frustrated Lewis pairs (FLPs) containing borenium cations have been synthesised. The catechol (Cat)‐ligated borenium cation [CatB(PtBu3)]+ has a lower hydride‐ion affinity (HIA) than B(C6F5)3. This resulted in H2 activation being energetically unfavourable in a FLP with the strong base PtBu3. However, ligand disproportionation of CatBH(PtBu3) at 100 °C enabled trapping of H2 activation products. DFT calculations at the M06‐2X/6‐311G(d,p)/PCM (CH2Cl2) level revealed that replacing catechol with chlorides significantly increases the chloride‐ion affinity (CIA) and HIA. Dichloro–borenium cations, [Cl2B(amine)]+, were calculated to have considerably greater HIA than B(C6F5)3. Control reactions confirmed that the HIA calculations can be used to successfully predict hydride‐transfer reactivity between borenium cations and neutral boranes. The borenium cations [Y(Cl)B(2,6‐lutidine)]+ (Y=Cl or Ph) form FLPs with P(mesityl)3 that undergo slow deprotonation of an ortho‐methyl of lutidine at 20 °C to form the four‐membered boracycles [(CH2{NC5H3Me})B(Cl)Y] and [HPMes3]+. When equimolar [Y(Cl)B(2,6‐lutidine)]+/P(mesityl)3 was heated under H2 (4 atm), heterolytic cleavage of dihydrogen was competitive with boracycle formation. 相似文献
18.
Bis[N,N′‐diisopropylbenzamidinato(−)]silicon(II): Lewis Acid/Base Reactions with Triorganylboranes
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Konstantin Junold Johannes A. Baus Dr. Christian Burschka Dr. Célia Fonseca Guerra Prof. Dr. F. Matthias Bickelhaupt Prof. Dr. Reinhold Tacke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(39):12411-12415
Reaction of the donor‐stabilized silylene 1 (which is three‐coordinate in the solid state and four‐coordinate in solution) with BEt3 and BPh3 leads to the formation of the Lewis acid/base complexes 2 and 3 , respectively, which are the first five‐coordinate silicon compounds with an Si?B bond. These compounds were structurally characterized by crystal structure analyses and by multinuclear NMR spectroscopic studies in the solid state and in solution. Additionally, the bonding situation in 2 and 3 was analyzed by quantum chemical studies. 相似文献
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A Germylene/Borane Lewis Pair and the Remarkable C=O Bond Cleavage Reaction toward Isocyanate and Ketone Molecules
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Jiancheng Li Bin Li Rui Liu Liuyin Jiang Prof. Dr. Hongping Zhu Prof. Dr. Herbert W. Roesky Sayan Dutta Dr. Debasis Koley Prof. Weiping Liu Qingsong Ye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(41):14499-14503
A germylene/borane Lewis pair ( 2 ) was prepared from a 1,1‐carboboration of amidinato phenylethynylgermylene ( 1 ) by B(C6F5)3. Compound 2 reacted with iPrNCO and (4‐MeOC6H4)C(O)Me, respectively, with cleavage of the C=O double bond. In the first instance, O and iPrNC insert separately into the Ge?B bond to yield a GeBC2O‐heterocycle ( 3 ) and a GeBC3‐heterocycle ( 4 ). In the second case (4‐MeOC6H4)(Me)C inserts into the Ge?N bond of 2 while O is incorporated in the Ge?B bond to form a Ge‐centered spiroheterocycle ( 5 ). The reaction of 2 with tBuNC to give 6 , which has almost the same structure as 4 , proved the formation of the isonitrile during transformation from 2 and iPrNCO to 3 and 4 . The kinetic study of the reaction of 2 and iPrNCO gave evidence of proceeding through a GeBC3O‐heterocycle intermediate. In addition, a DFT study was performed to elucidate the reaction mechanism. 相似文献
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Tatsuyoshi Ito Nobuharu Iwasawa Jun Takaya 《Angewandte Chemie (International ed. in English)》2020,59(29):11913-11917
An unprecedented photo‐promoted skeletal rearrangement reaction of phosphine–borane frustrated Lewis pairs, o‐(borylaryl)phosphines, involving cleavage of an unstrained sp2C–sp3C σ‐bond is reported. The reaction realizes an efficient synthesis of cyclic phosphonium borate compounds. The reaction mechanism via a boranorcaradiene intermediate is proposed based on theoretical calculations. This work sheds light on the new photoreactivity of phosphine–borane FLPs. 相似文献