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1.
Valiallah Hosseininasab Alison C. McQuilken Abolghasem Bakhoda Jeffery A. Bertke Qadir K. Timerghazin Timothy H. Warren 《Angewandte Chemie (International ed. in English)》2020,59(27):10854-10858
S‐Nitrosothiols (RSNOs) serve as air‐stable reservoirs for nitric oxide in biology. While copper enzymes promote NO release from RSNOs by serving as Lewis acids for intramolecular electron‐transfer, redox‐innocent Lewis acids separate these two functions to reveal the effect of coordination on structure and reactivity. The synthetic Lewis acid B(C6F5)3 coordinates to the RSNO oxygen atom, leading to profound changes in the RSNO electronic structure and reactivity. Although RSNOs possess relatively negative reduction potentials, B(C6F5)3 coordination increases their reduction potential by over 1 V into the physiologically accessible +0.1 V vs. NHE. Outer‐sphere chemical reduction gives the Lewis acid stabilized hyponitrite dianion trans‐[LA‐O‐N=N‐O‐LA]2? [LA=B(C6F5)3], which releases N2O upon acidification. Mechanistic and computational studies support initial reduction to the [RSNO‐B(C6F5)3] radical anion, which is susceptible to N?N coupling prior to loss of RSSR. 相似文献
2.
The reactivity of the free aluminylene [N]-Al ( 1 ) ([N]=1,8-bis(3,5-di-tert-butylphenyl)-3,6-di-tert-butylcarbazolyl) towards boron Lewis acids is investigated. A facile oxidative addition reaction of 1 with Ph2BOBPh2 furnishes an exceedingly scarce example of the free alumaborane [N]-Al(BPh2)(OBPh2) ( 2 ) with an Al−B electron-sharing bond. By contrast, complexation of 1 with B(C6F5)3 and HB(C6F5)2 gives rise to the corresponding Lewis adducts [N]-Al→B(C6F5)3 ( 3 ) and [N]-Al→BH(C6F5)2 ( 4 ), respectively, with an Al→B dative bond. Crystallization of 4 in Et2O produces the adduct [N]-Al(Et2O)→BH(C6F5)2 ( 5 ). Quantum chemical calculations are carried out to understand the formation of 2 as well as the bonding situation of 3 and 5 . 相似文献
3.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(45):14362-14365
The reactions of the phosphaethynolate anion ([PCO]−) with a range of boranes were explored. BPh3 and [PCO]− form a dimeric anion featuring P−B bonds and is prone to dissociation at room temperature. The more Lewis acidic borane B(C6F5)3 yields a less symmetric dimer of [PCO]− with P−B and P−O bonds. Less sterically demanding HB(C6F5)2 and H2B(C6F5) boranes form a third isomer with [PCO]− featuring both boranes bound to the same phosphorus atom. Despite the unexpected thermodynamic preference for P‐coordination, computational data illustrate that electronic and steric features impact the binding modes of the resulting dianionic dimers. 相似文献
4.
Dr. Masatoshi Shibuya Miki Matsuda Prof. Yoshihiko Yamamoto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(34):8822-8831
We report the novel single-step 1,2-dicarbofunctionalization of an arylacetylene with an allylsilane and tris(pentafluorophenyl)borane [B(C6F5)3] involving C−C bond formation with C−H bond scission at the β-position to the silicon atom of an allylsilane and B→C migration of a C6F5 group. The 1,2-carbopentafluorophenylation occurs smoothly without the requirement for a catalyst or heating. Mechanistic studies suggest that the metallomimetic “pull-push” reactivity of B(C6F5)3 imparts consecutive electrophilic and nucleophilic characteristics to the benzylic carbon of the arylacetylene. Subsequent photochemical 6π-electrocyclization affords tetrafluoronaphthalenes, which are important in the pharmaceutical and materials sciences. Owing to the unique reactivity of B(C6F5)3, the 1,2-carbopentafluorophenylation using 2-substituted furan proceeded with ring opening, and the reaction using silyl enolates formed a C−C bond with C−O bond scission at the silyloxy-substituted carbon. 相似文献
5.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(40):12436-12440
The reaction of trans ‐[M(N2)2(dppe)2] (M=Mo, 1Mo , M=W, 1W ) with B(C6F5)3 ( 2 ) provides the adducts [(dppe)2M=N=N‐B(C6F5)3] ( 3 ) which can be regarded as M/B transition‐metal frustrated Lewis pair (TMFLP) templates activating dinitrogen. Easy borylation and silylation of the activated dinitrogen ligands in complexes 3 with a hydroborane and hydrosilane occur by splitting of the B−H and Si−H bonds between the N2 moiety and the perfluoroaryl borane. This reactivity of 3 is reminiscent of conventional frustrated Lewis pair chemistry and constitutes an unprecedented approach for the functionalization of dinitrogen. 相似文献
6.
Youngsuk Kim Dr. Liu Leo Liu Prof. Dr. Douglas W. Stephan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(29):7110-7113
N-Heterocyclic carbene (NHC) derived 3-azabutadienes 1 and 2 have been prepared by a single-step reaction of the corresponding NHC with cyclohexyl isocyanide. Compound 1 features π-basic, delocalized nucleophilic sites over the 3-azabutadiene moiety, therefore allowing for coordinating with small Lewis acids, such as AlCl3, GaCl3, and Me2SAuCl, to form diverse classic Lewis adducts 3 – 5 . Combination of 1 with B(C6F5)3 or [Ph3C][B(C6F5)4] resulted in single-electron transfer and the obtained radical cation was detected by EPR. In addition, a frustrated Lewis pair comprised of the π-basic 1 and BPh3 effects the splitting of the O−H bond of phenol and the N−H bond of imidazole to give 7 and 8 , respectively. An intrinsic bond orbital (IBO) analysis of the pathway leading to 8 showcases the transformation of the delocalized π-electrons of 1 to a newly formed C−H localized σ-bond. 相似文献
7.
Angela Milinkovic Dr. Antoine Dupé Ao. Univ.-Prof. Dr. Ferdinand Belaj Univ.-Prof. Dr. Nadia C. Mösch-Zanetti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(55):e202201867
Molybdenum(VI) bis(imido) complexes [Mo(NtBu)2(LR)2] (R=H 1 a ; R=CF3 1 b ) combined with B(C6F5)3 ( 1 a /B(C6F5)3, 1 b /B(C6F5)3) exhibit a frustrated Lewis pair (FLP) character that can heterolytically split H−H, Si−H and O−H bonds. Cleavage of H2 and Et3SiH affords ion pairs [Mo(NtBu)(NHtBu)(LR)2][HB(C6F5)3] (R=H 2 a ; R=CF3 2 b ) composed of a Mo(VI) amido imido cation and a hydridoborate anion, while reaction with H2O leads to [Mo(NtBu)(NHtBu)(LR)2][(HO)B(C6F5)3] (R=H 3 a ; R=CF3 3 b ). Ion pairs 2 a and 2 b are catalysts for the hydrosilylation of aldehydes with triethylsilane, with 2 b being more active than 2 a . Mechanistic elucidation revealed insertion of the aldehyde into the B−H bond of [HB(C6F5)3]−. We were able to isolate and fully characterize, including by single-crystal X-ray diffraction analysis, the inserted products Mo(NtBu)(NHtBu)(LR)2][{PhCH2O}B(C6F5)3] (R=H 4 a ; R=CF3 4 b ). Catalysis occurs at [HB(C6F5)3]− while [Mo(NtBu)(NHtBu)(LR)2]+ (R=H or CF3) act as the cationic counterions. However, the striking difference in reactivity gives ample evidence that molybdenum cations behave as weakly coordinating cations (WCC). 相似文献
8.
《Angewandte Chemie (International ed. in English)》2017,56(39):11995-11999
This work showcases a new catalytic cyclization reaction using a highly Lewis acidic borane with concomitant C−H or C−C bond formation. The activation of alkyne‐containing substrates with B(C6F5)3 enabled the first catalytic intramolecular cyclizations of carboxylic acid substrates using this Lewis acid. In addition, intramolecular cyclizations of esters enable C−C bond formation as catalytic B(C6F5)3 can be used to effect formal 1,5‐alkyl migrations from the ester functional groups to unsaturated carbon–carbon frameworks. This metal‐free method was used for the catalytic formation of complex dihydropyrones and isocoumarins in very good yields under relatively mild conditions with excellent atom efficiency. 相似文献
9.
Haopeng Gao Dr. Robert Müller Dr. Elisabeth Irran Dr. Hendrik F. T. Klare Prof. Dr. Martin Kaupp Prof. Dr. Martin Oestreich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(12):e202104464
Potent main-group Lewis acids are capable of activating element-hydrogen bonds. To probe the rivalry for hydride between silylium- and borenium-ion centers, a neutral precursor with the hydrosilane and hydroborane units in close proximity on a naphthalene-1,8-diyl platform was designed. Abstraction of one hydride leads to a hydroborane-stabilized silylium ion rather than a hydrosilane-coordinated borenium ion paired with [B(C6F5)4]− or [HCB11Cl11]− as counteranions. Characterization by multinuclear NMR spectroscopy and X-ray diffraction supported by DFT calculations reveals a cationic, unsymmetrical open three-center, two-electron (3c2e) Si−H−B linkage. 相似文献
10.
Jinxiong Lin Dr. Friedrich Wossidlo. Dr. Nathan T. Coles Manuela Weber Dr. Simon Steinhauer Priv.-Doz. Dr. Tobias Böttcher Prof. Dr. Christian Müller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(7):e202104135
A phosphinine-borane adduct of a Me3Si-functionalized phosphinine and the Lewis acid B(C6F5)3 has been synthesized and characterized crystallographically for the first time. The reaction strongly depends on the nature of the substituents in the α-position of the phosphorus heterocycle. In contrast, the reaction of B2H6 with various substituted phosphinines leads to an equilibrium between the starting materials and the phosphinine–borane adducts that is determined by the Lewis basicity of the phosphinine. The novel phosphinine borane adduct ( 6 -B(C6F5)3) shows rapid and facile insertion and [4+2] cycloaddition reactivity towards phenylacetylene. A hitherto unknown dihydro-1-phosphabarrelene is formed with styrene. The reaction with an ester provides a new, facile and selective route to 1-R-phosphininium salts. These salts then undergo a [4+2] cycloaddition in the presence of Me3Si−C≡CH and styrene to cleanly form unprecedented derivatives of 1-R-phosphabarrelenium salts. 相似文献
11.
Jean-Charles Bruyere Dr. David Specklin Dr. Christophe Gourlaouen Dr. Rosita Lapenta Prof. Luis F. Veiros Prof. Alfonso Grassi Dr. Stefano Milione Prof. Laurent Ruhlmann Prof. Corinne Boudon Dr. Samuel Dagorne 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(34):8061-8069
The reactivity of ZnII dialkyl species ZnMe2 with a cyclic(alkyl)(amino)carbene, 1-[2,6-bis(1-methylethyl)phenyl]-3,3,5,5-tetramethyl-2-pyrrolidinylidene (CAAC, 1 ), was studied and extended to the preparation of robust CAAC-supported ZnII Lewis acidic organocations. CAAC adduct of ZnMe2 ( 2 ), formed from a 1:1 mixture of 1 and ZnMe2, is unstable at room temperature and readily undergoes a CAAC carbene insertion into the Zn−Me bond to produce the ZnX2-type species (CAAC-Me)ZnMe ( 3 ), a reactivity further supported by DFT calculations. Despite its limited stability, adduct 2 was cleanly ionized to robust two-coordinate (CAAC)ZnMe+ cation ( 5+ ) and derived into (CAAC)ZnC6F5+ ( 7+ ), both isolated as B(C6F5)4− salts, showing the ability of CAAC for the stabilization of reactive [ZnMe]+ and [ZnC6F5]+ moieties. Due to the lability of the CAAC−ZnMe2 bond, the formation of bis(CAAC) adduct (CAAC)2ZnMe+ cation ( 6+ ) was also observed and the corresponding salt [ 6 ][B(C6F5)4] was structurally characterized. As estimated from experimental and calculations data, cations 5+ and 7+ are highly Lewis acidic species and the stronger Lewis acid 7+ effectively mediates alkene, alkyne and CO2 hydrosilylation catalysis. All supporting data hints at Lewis acid type activation–functionalization processes. Despite a lower energy LUMO in 5+ and 7+ , their observed reactivity is comparable to those of N-heterocyclic carbene (NHC) analogues, in line with charge-controlled reactions for carbene-stabilized ZnII organocations. 相似文献
12.
Dr. Yile Wu Zhao Zhao Dr. Ting Chen Jingjie Tan Dr. Zheng-Wang Qu Prof. Dr. Stefan Grimme Prof. Dr. Yufen Zhao Prof. Dr. Douglas W. Stephan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(25):e202200666
The germylene species (CH{(CMe)(2,6-iPr2C6H3N)}2)GePCO 1 is shown to react with the Lewis acids (E(C6F5)3 E=B, Al). Nonetheless, 1 participates in FLP chemistry with electron deficient alkynes or olefins, acting as an intramolecular FLP. In contrast, in the presence of B(C6F5)3 and an electron rich alkyne, 1 behaves as Ge-based nucleophile to effect intermolecular FLP addition to the alkyne. This reactivity demonstrates that the reaction pathway is controlled by the nature of the electrophile and nucleophile generated in solution, as revealed by extensive DFT calculations. 相似文献
13.
Jens Rudlof Niklas Aders Dr. Jan-Hendrik Lamm Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Norbert W. Mitzel 《ChemistryOpen》2021,10(10):1020-1027
Starting from 1,2-diethynylbenzene, a series of bidentate Lewis acids was prepared by means of hydrometalations, in particular hydrosilylation, hydroboration, hydroalumination and terminal metalation based on group 13 and 14 elements. In the case of terminal alkyne metalation, the Lewis-acidic gallium function was introduced using triethylgallium under alkane elimination. A total of six different Lewis acids based on a semiflexible organic scaffold were prepared, bearing −SiClMe2, −SiCl2Me, −SiCl3, −B(C6F5)2, −AlBis2 (Bis=bis(trimethylsilyl)methyl) and −GaEt2 as the corresponding functional units. In all cases, the Lewis acid functionalisation was carried out twice and the products were obtained in good to excellent yields. In the case of the twofold gallium Lewis acid, a different structural motif in the form of a polymer-like chain was observed in the solid state. All new bidentate Lewis acids were characterised by multinuclear NMR spectroscopy, CHN analysis and X-ray diffraction experiments. 相似文献
14.
Directly Bridging Indoles to 3,3′‐Bisindolylmethanes by Using Carboxylic Acids and Hydrosilanes under Mild Conditions
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《化学:亚洲杂志》2018,13(18):2664-2670
A straightforward Lewis acid‐promoted protocol for 3,3′‐bisindolylmethanes (BIMs) synthesis by reductive alkylation of indoles at the C3 position with carboxylic acids in the presence of hydrosilane was developed for the first time. Instead of aldehydes, more readily available, stable, and easy‐to‐handle carboxylic acids have been employed as alternative alkylating agents. As an efficient organocatalyst, B(C6F5)3 enables the reductive alkylation of various substituted indole derivatives with carboxylic acids with up to 98 % yield at room temperature and under neat conditions. This metal‐free strategy offers an alternative approach for the direct functionalization of indoles to BIMs with carboxylic acids and such protocol allows selective reduction of carboxylic acid to aldehyde in combination with C−C bond formation. 相似文献
15.
Autoinduced Catalysis and Inverse Equilibrium Isotope Effect in the Frustrated Lewis Pair Catalyzed Hydrogenation of Imines
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Dipl.‐Chem. Sebastian Tussing Dr. Lutz Greb Dipl.‐Chem. Sergej Tamke Dr. Birgitta Schirmer Priv.‐Doz. Claudia Muhle‐Goll Prof. Dr. Burkhard Luy Prof. Dr. Jan Paradies 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8056-8059
The frustrated Lewis pair (FLP)‐catalyzed hydrogenation and deuteration of N‐benzylidene‐tert‐butylamine ( 2 ) was kinetically investigated by using the three boranes B(C6F5)3 ( 1 ), B(2,4,6‐F3‐C6H2)3 ( 4 ), and B(2,6‐F2‐C6H3)3 ( 5 ) and the free activation energies for the H2 activation by FLP were determined. Reactions catalyzed by the weaker Lewis acids 4 and 5 displayed autoinductive catalysis arising from a higher free activation energy (2 kcal mol?1) for the H2 activation by the imine compared to the amine. Surprisingly, the imine reduction using D2 proceeded with higher rates. This phenomenon is unprecedented for FLP and resulted from a primary inverse equilibrium isotope effect. 相似文献
16.
A Combined “Electrochemical–Frustrated Lewis Pair” Approach to Hydrogen Activation: Surface Catalytic Effects at Platinum Electrodes
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Elliot J. Lawrence Dr. Robin J. Blagg Dr. David L. Hughes Dr. Andrew E. Ashley Dr. Gregory G. Wildgoose 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):900-906
Herein, we extend our “combined electrochemical–frustrated Lewis pair” approach to include Pt electrode surfaces for the first time. We found that the voltammetric response of an electrochemical–frustrated Lewis pair (FLP) system involving the B(C6F5)3/[HB(C6F5)3]? redox couple exhibits a strong surface electrocatalytic effect at Pt electrodes. Using a combination of kinetic competition studies in the presence of a H atom scavenger, 6‐bromohexene, and by changing the steric bulk of the Lewis acid borane catalyst from B(C6F5)3 to B(C6Cl5)3, the mechanism of electrochemical–FLP reactions on Pt surfaces was shown to be dominated by hydrogen‐atom transfer (HAT) between Pt, [Pt?H] adatoms and transient [HB(C6F5)3] ? electrooxidation intermediates. These findings provide further insight into this new area of combining electrochemical and FLP reactions, and proffers additional avenues for exploration beyond energy generation, such as in electrosynthesis. 相似文献
17.
Accessing Frustrated Lewis Pair Chemistry from a Spectroscopically Stable and Classical Lewis Acid‐Base Adduct
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Dr. Timothy C. Johnstone Gabriel N. J. H. Wee Prof. Dr. Douglas W. Stephan 《Angewandte Chemie (International ed. in English)》2018,57(20):5881-5884
B(C6F5)3 and P(MeNCH2CH2)3N form a classical Lewis adduct, (C6F5)3BP(MeNCH2CH2)3N. Although (C6F5)3BP(MeNCH2CH2)3N does not exhibit spectroscopic evidence of dissociation into its constituent acid and base, products of frustrated Lewis pair (FLP) addition reactions are seen with PhNCO, PhCH2N3, PhNSO, and CO2. Computational studies show that thermal access to the dissociated acid and base permits FLP reactivity to proceed. These results demonstrate that FLP reactivity extends across the entire continuum of equilibria governing Lewis acid‐base adducts. 相似文献
18.
Anaïs Coffinet Dr. David Specklin Dr. Laure Vendier Prof. Dr. Michel Etienne Dr. Antoine Simonneau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(63):14300-14303
The first example of a formal 1,3-B−H bond addition across the M−N≡N unit of an end-on dinitrogen complex has been achieved. The use of Piers’ borane HB(C6F5)2 was essential to observe this reactivity and it plays a triple role in this transformation: 1) electrophilic N2-borylation agent, 2) Lewis acid in a frustrated Lewis pair-type B−H bond activation, and 3) hydride shuttle to the metal center. This chemistry is supported by NMR spectroscopy and solid-state characterization of products and intermediates. The combination of chelate effect and strong σ donation in the diphosphine ligand 1,2-bis(diethylphosphino)ethane was mandatory to avoid phosphine dissociation that otherwise led to complexes where borylation of N2 occurred without hydride transfer. 相似文献
19.
Corina Stoian Dr. Marian Olaru Teodor A. Cucuiet Krisztina T. Kegyes Alexandru Sava Prof. Dr. Alexey Y. Timoshkin Prof. Dr. Ciprian I. Raţ Prof. Dr. Jens Beckmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(13):4327-4331
Protocols for the synthesis of the bulky polyfluorinated triarylboranes 2,6-(C6F5)2C6F3B(C6F5)2 ( 1 ), 2,6-(C6F5)2C6F3B[3,5-(CF3)2C6H3] ( 2 ), 2,4,6-(C6F5)3C6H2B(C6F5)2 ( 3 ), 2,4,6-(C6F5)3C6H2B[3,5-(CF3)2C6H3] ( 4 ) were developed. All boranes are water tolerant and according to the Gutmann-Beckett method, 1 – 3 display Lewis acidities larger than that of the prominent B(C6F5)3. 相似文献
20.
Stereochemical Behavior of Pairs of P-stereogenic Phosphanyl Groups at the Dimethylxanthene Backbone
Dr. Karel Škoch Dr. Constantin G. Daniliuc Marcel Müller Prof. Dr. Stefan Grimme Dr. Gerald Kehr Prof. Dr. Gerhard Erker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(20):e202200248
The P-stereogenic bis(phosphanes) 7 and 9 , featuring pairs of P(Mes)-ethynyl or vinyl substituents at the dimethyl xanthene backbone show rather low barriers of stereochemical inversion at phosphorus. π-Conjugative effects are probably causing these low inversion barriers. Compound 7 reacted with B(C6F5)3 to form the nine-membered heterocyclic product 10 , featuring a [P]−C≡C−B(C6F5)3 substituent. Compound 7 was converted to the bis[P(Mes)vinyl] xanthene derivative 9 , which gave the zwitterionic P(H)(Mes)−CH=CH−B(C6F5)3 containing product 16 upon treatment with B(C6F5)3. Thermally induced epimerization barriers at phosphorus of ca. 20 to 27 kcal mol−1 were calculated by DFT for the alkenyl- and alkynyl-P derived systems 6 to 9 , 15 and 16 and experimentally determined for the examples 7 and 16 . 相似文献