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1.
Aurlien Chardon Arnaud Osi Damien Mahaut Thu‐Hong Doan Nikolay Tumanov Johan Wouters Luca Fusaro Benoît Champagne Guillaume Berionni 《Angewandte Chemie (International ed. in English)》2020,59(30):12402-12406
A highly bent triarylborane, 9‐boratriptycene, was generated in solution by selective protodeboronation of the corresponding tetra‐aryl boron ate complex with the strong Brønsted acid HNTf2. The iptycene core confers enhanced Lewis acidity to 9‐boratriptycene, making it unique in terms of structure and reactivity. We studied the stereoelectronic properties of 9‐boratriptycene by quantifying its association with small N‐ and O‐centered Lewis bases, as well as with sterically hindered phosphines. The resultant Lewis adducts exhibited unique structural, spectroscopic, and photophysical properties. Beyond the high pyramidalization of the 9‐boratriptycene scaffold and its low reorganization energy upon Lewis base coordination, quantum chemical calculations revealed that the absence of π donation from the triptycene aryl rings to the boron vacant pz orbital is one of the main reasons for its high Lewis acidity. 相似文献
2.
Mika Sakai Masayoshi Mori Dr. Masato Hirai Dr. Naoki Ando Prof. Dr. Shigehiro Yamaguchi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(38):e202200728
Two kinds of planarized phenyldithienylboranes, which contain (CH3)2C- or CH2-bridging moieties, were synthesized. The difference of the bridging moieties affects their packing structures and photophysical properties. In particular, the (CH3)2C-bridged derivative exhibits a large Stokes shift, unusual for such planarized compounds, that results from a large structural relaxation in the excited state. A series of π-extended derivatives was synthesized, among which a p-(diphenylamino)phenyl-substituted derivative shows large solvatochromism in the fluorescence spectra, while maintaining high quantum yields even in polar solvents. The Lewis acidity of the phenyldithienylborane derivatives was also assessed by titration with pyridine. The Lewis acidity of the boron center is affected not only by the difference in the steric bulk of the bridging moieties, but also by the electronic effect of the substituents introduced at remote positions relative to the boron atom. These results demonstrate the characteristic features of planarized phenyldithienylboranes as building blocks for boron-based π-electron materials. 相似文献
3.
Lewis acidity trend of boron trihalides is a subject that has received a variety of explanations, and still, the simple π back-bonding based one is believed by most, perhaps because of its simplicity, irrespective of opposing findings. Herein we try to give an alternative explanation based on qualitative Molecular Orbital (MO) theory and support that quantitatively by Generalized Kohn-Sham Energy Decomposition Analysis. While the role of orbital overlap on the orbital interaction energy is widely known, the role of electronegativity of the atoms involved is often overlooked. Here we find that the Lewis acidity trend of boron and aluminium halides can be explained by the Wolfsberg-Helmholz (W−H) formula for resonance integral. The MO theory-based predictions are valid only when the orbital interactions are strong enough. In weakly interacting systems, the effect of orbital interactions can be overshadowed by other effects such as Pauli repulsion, dispersion, etc. Thus the Lewis acidity trend of boron and aluminium halides can vary depending on the strength of the interacting Lewis base. We believe that this work would enable one to gain a better understanding not only on the Lewis acidity of boron trihalides and its heavy analogs but also on a variety of related problems such as the stronger π acidity of CS compared to CO and weaker π bonding between heavy atoms. 相似文献
4.
Yasuda M Nakajima H Takeda R Yoshioka S Yamasaki S Chiba K Baba A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(14):3856-3867
Boron complexes that contain new tridentate ligands, tris(o‐oxyaryl)methanes and ‐silanes, were prepared. These complexes had a cage‐shaped structure around a boron center and showed higher Lewis acidity and catalytic activity than open‐shaped boron compounds. The cage‐shaped ligands determined the properties of the borates by altering the geometry and were consistently bound to the metal center by chelation. The synthesized compounds were L?B(OC6H4)3CH, L?B(OC6H4)3SiMe, and its derivatives (L=THF or pyridine as an external ligand). Theoretical calculations suggested that the cage‐shaped borates had a large dihedral angle (Cipso‐O‐B‐O) compared with open‐shaped borates. The geometric effect due to the dihedral angle means that compared with open‐shaped, the cage‐shaped borates have a greater Lewis acidity. The introduction of electron‐withdrawing groups on the aryl moieties in the cage‐shaped framework increased the Lewis acidity. Substitution of a bridgehead Si for a bridgehead C decreased the Lewis acidity of the boron complexes because the large silicon atom reduces the dihedral angle of Cipso‐O‐B‐O. The ligand‐exchange rates of the para‐fluoro‐substituted compound B(OC6H3F)3CH and the ortho‐phenyl‐substituted compound B(OC6H3Ph)3CH were less than that of the unsubstituted borate B(OC6H4)3CH. The ligand‐exchange rate of B(OC6H4)3SiMe was much faster than that of B(OC6H4)3CH. A hetero Diels–Alder reaction and Mukaiyama‐type aldol reactions were more effectively catalyzed by cage‐shaped borates than by the open‐shaped borate B(OPh)3 or by the strong Lewis acid BF3?OEt2. The cage‐shaped borates with the bulky substituents at the ortho‐positions selectively catalyzed the reaction with less sterically hindered substrates, while the unsubstituted borate showed no selectivity. 相似文献
5.
Weiwei Lv Yuyang Dai Rui Guo Prof. Dr. Yuanting Su Dr. David A. Ruiz Prof. Dr. Liu Leo Liu Prof. Dr. Chen-Ho Tung Prof. Dr. Lingbing Kong 《Angewandte Chemie (International ed. in English)》2023,62(36):e202308467
This report unveils an advancement in the formation of a Lewis superacid (LSA) and an organic superbase by the geometrical deformation of an organoboron species towards a T-shaped geometry. The boron dication [ 2 ]2+ supported by an amido diphosphine pincer ligand features both a large fluoride ion affinity (FIA>SbF5) and hydride ion affinity (HIA>B(C6F5)3), which qualifies it as both a hard and soft LSA. The unusual Lewis acidic properties of [ 2 ]2+ are further showcased by its ability to abstract hydride and fluoride from Et3SiH and AgSbF6 respectively, and effectively catalyze the hydrodefluorination, defluorination/arylation, as well as reduction of carbonyl compounds. One and two-electron reduction of [ 2 ]2+ affords stable boron radical cation [ 2 ]⋅+ and borylene 2 , respectively. The former species has an extremely high spin density of 0.798e at the boron atom, whereas the latter compound has been demonstrated to be a strong organic base (calcd. pKBH+ (MeCN)=47.4) by both theoretical and experimental assessment. Overall, these results demonstrate the strong ability of geometric constraining to empower the central boron atom. 相似文献
6.
Ali Ben Saida Aurlien Chardon Arnaud Osi Nikolay Tumanov Johan Wouters Abel I. Adjieufack Benoît Champagne Guillaume Berionni 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(47):17045-17049
Bending the planar trigonal boron center of triphenylborane by connecting its aryl rings with carbon or phosphorus linkers gave access to a series of 9‐boratriptycene derivatives with unprecedented structures and reactivities. NMR spectroscopy and X‐ray diffraction of the Lewis adducts of these non‐planar boron Lewis acids with weak Lewis base revealed particularly strong covalent bond formation. The first Lewis adduct of a trivalent boron compounds with the Tf2N? anion illustrates the unrivaled Lewis acidity of these species. Increasing the pyramidalization of the boron center and using a cationic phosphonium linker resulted in an exceptional enhancement of Lewis acidity. Introduction of a phosphorus and a boron atom at each edge of a triptycene framework, allowed access to new bifunctional Lewis acid‐base 9‐phospha‐10‐boratriptycenes featuring promising reactivity for the activation of carbon‐halogen bonds. 相似文献
7.
8.
Idan Avigdori Dr. Alla Pogoreltsev Dr. Alexander Kaushanski Dr. Natalia Fridman Prof. Dr. Mark Gandelman 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(52):23682-23685
N-heterocyclic nitrogen Lewis acids are a recent addition to the field of organic chemistry. Based on nitrenium cations, these acids where previously shown to generate Lewis adducts when combined with the appropriate Lewis bases. Herein, a triazinium-based Lewis acid was combined with tBu3P to generate a frustrated Lewis pair (FLP) capable of cleaving, for the first time, Si−H bonds in silanes. Whereas low yields were initially encountered owing to insufficient Lewis acidity, a new nitrenium-based Lewis acid was synthesized, and its superior Lewis acidity was experimentally and computationally confirmed. A FLP based on this acid cleaved the Si−H bond in PhSiH3, generating the triazane product in a quantitative yield. This unprecedented N−H triazane was fully characterized by multinuclear NMR techniques and single-crystal X-ray crystallography. A new class of compounds, N-H triazanes display the potential capacity to participate in hydride transfer reactions. 相似文献
9.
Prof. Dr. Holger Braunschweig Dr. Rian D. Dewhurst Leanne Pentecost Dr. Krzysztof Radacki Dr. Alfredo Vargas Dr. Qing Ye 《Angewandte Chemie (International ed. in English)》2016,55(1):436-440
An electron‐rich monovalent boron compound is used as a Lewis base to prepare adducts with Group 13 Lewis acids using both its boron and nitrogen sites. The hard Lewis acid AlCl3 binds through a nitrogen atom of the Lewis base, while softer Lewis acids GaX3 (Cl, Br, I) bind at the boron atom. The latter are the first noncluster Lewis adducts between a boron‐centered Lewis base and a main‐group Lewis acid. 相似文献
10.
Nitrogen‐Based Lewis Acids: Synthesis and Reactivity of a Cyclic (Alkyl)(Amino)Nitrenium Cation 下载免费PDF全文
Dr. Jiliang Zhou Dr. Liu Leo Liu Levy L. Cao Prof. Dr. Douglas W. Stephan 《Angewandte Chemie (International ed. in English)》2018,57(13):3322-3326
A room‐temperature‐stable crystalline cyclic (alkyl)(amino)nitrenium cation 2 features cationic nitrogen atom with a smaller HOMO–LUMO gap compared to that of a 1,2,3‐triazolium 5 (an N‐heterocyclic nitrenium cation). The low‐lying LUMO of 2 results in an enhanced electrophilicity, which allowed for the formation of Lewis adducts with neutral Lewis bases, such as Me3P, nBu3P, and IiPr. The N‐based Lewis acid 2 also forms an FLP with tBu3P but subsequently reacts with (PrS)2 to cleave the S?S bond. Both experimental and theoretical results suggest that the Lewis acidity of 2 is stronger than its N3 analogues. 相似文献
11.
Fabrizio Medici Julien Maury Dr. Gilles Lemière Prof. Louis Fensterbank 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(40):9438-9442
In this work, the interaction between Lewis bases, especially N-heterocyclic carbenes (NHCs), and hindered neutral silicon derivatives featuring high Lewis acidity is described. The formation of normal and abnormal Lewis adducts could be controlled by varying the acidity of the corresponding tetravalent spiro organosilane. Some DFT calculations permitted to gain insight into the thermodynamics of the NHC–spirosilane interaction featuring various NHCs differing in size and σ-donor capacity. Spirosilanes are introduced as new Lewis partners in frustrated Lewis pair (FLP) chemistry and some FLP-type reactivities are presented, in particular the activation of formaldehyde that could occur with both hindered NHCs and phosphines. 相似文献
12.
Sesime Coffie James M. Hogg Lucie Cailler Dr. Albert Ferrer‐Ugalde Richard W. Murphy Dr. John D. Holbrey Dr. Fergal Coleman Dr. Małgorzata Swadźba‐Kwaśny 《Angewandte Chemie (International ed. in English)》2015,54(49):14970-14973
The first examples of ionic liquids based on borenium cations, [BCl2L]+, are reported. These compounds form highly Lewis acidic liquids under solvent‐free conditions. Their acidity was quantified by determining the Gutmann acceptor number (AN). Extremely high ANs were recorded (up to AN=182, δ31P=120 ppm), demonstrating that these borenium ionic liquids are the strongest Lewis superacids reported to date, with the acidity enhanced by the ionic liquid environment. 相似文献
13.
Riddhi R. Golwankar Dr. Amit Kumar Dr. Victor W. Day Prof. James D. Blakemore 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(38):e202200344
Incorporation of redox-inactive metals into redox-active complexes and catalysts attracts attention for engendering new reactivity modes, but this strategy has not been extensively investigated beyond the first-row of the transition metals. Here, the isolation and characterization of the first series of heterobimetallic complexes of palladium with mono-, di-, and tri-valent redox-inactive metal ions are reported. A Reinhoudt-type heteroditopic ligand with a salen-derived [N2,O2] binding site for Pd and a crown-ether-derived [O6] site has been used to prepare isolable adducts of the Lewis acidic redox-inactive metal ions ( M n+). Comprehensive data from single-crystal X-ray diffraction analysis reveal distinctive trends in the structural properties of the heterobimetallic species, including an uncommon dependence of the Pd⋅⋅⋅ M distance on Lewis acidity. The reorganization energy associated with reduction of the heterobimetallic species is strongly modulated by Lewis acidity, with the slowest heterogeneous electron transfer kinetics associated with the strongest incorporated Lewis acids. This hitherto unexplored reorganization energy penalty for electron transfer contrasts with prior thermodynamic studies, revealing that kinetic parameters should be considered in studies of reactivity involving heterobimetallic species. 相似文献
14.
Jiazhuang Chen Yuke Zhong Dr. Yalan Liu Dr. Lei Zhang Dr. Mei Li Dr. Wei Han Prof. Zhifang Chai Prof. Weiqun Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(42):e202200443
AlCl3-NaCl was utilized as an electrolyte in this work due to its low melting point and Lewis acidity, in which samarium exists in two oxidation states, Sm(III) and Sm(II), resulting in unique electrochemical behaviours. Sm metal dissolves in AlCl3-NaCl melt to form SmCl2, which is verified by electrochemical and spectroscopic techniques. As the Lewis acidity of the melt increases, the diffusion coefficient of Sm(II) gradually increases, and the activation energy of diffusion decreases. Moreover, an additional co-reduction peak of Sm3+ and AlCl4− is observed to be more positive than that of Al(0)/Al(III) in Lewis basic melt, which may be tightly correlated with the variation of Sm(II) coordination in AlCl3-NaCl melt and ligand variation from Cl− to AlCl4− and Al2Cl7− as the Lewis acidity of the AlCl3-NaCl melt increases, according to the in situ electronic absorption spectra of Sm in this melt. 相似文献
15.
The Lewis acidity scale of boron trihalides BX3 (X=F, C1, Br, I) and character of the boron-halogen bonds have been studied by means of DV-Xm approach. Present results show that the acid strength of boron trihalides increases in the order BF3<BCl3<BBr3<BI3, in excellent agreement with experiments. Based on boron-halogen bonding character, the valence of boron atom in boron compounds can be considered M equal to five instead of three which seems to be more reasonable. 相似文献
16.
P.Darrell Ownby 《Journal of solid state chemistry》2004,177(2):466-470
The separation of the boron isotopes using boron trifluoride·organic-donor, Lewis acid·base adducts is an essential first step in preparing 10B enriched and depleted crystalline solids so vital to nuclear studies and reactor applications such as enriched MgB2, boron carbide, ZrB2, HfB2, aluminum boron alloys, and depleted silicon circuits for radiation hardening and neutron diffraction crystal structure studies. The appearance of this new adduct with such superior properties demands attention in the continuing search for more effective and efficient means of separation. An evaluation of the boron trifluoride nitromethane adduct, its thermodynamic and physical properties related to large-scale isotopic separation is presented. Its remarkably high separation factor was confirmed to be higher than the expected theoretical value. However, the reportedly high acid/donor ratio was proven to be an order of magnitude lower. On-going research is determining the crystal structure of deuterated and 11B enriched 11BF3·CD3NO2 by X-ray and neutron diffraction. 相似文献
17.
Laura Köring Dr. Arne Stepen Dr. Bernhard Birenheide Simon Barth Maxim Leskov Dr. Roland Schoch Dr. Felix Krämer Prof. Dr. Frank Breher Prof. Dr. Jan Paradies 《Angewandte Chemie (International ed. in English)》2023,62(13):e202216959
A series of redox-responsive ferrocenyl-substituted boranes and boronic esters were synthesized. Oxidation of the ferrocenyl ligand to the ferrocenium resulted in a drastic increase in the Lewis acidity beyond the strength of SbF5, which was investigated experimentally and computationally. The resulting highly Lewis acidic boron compounds were used for catalytic C−F and S−F bond activation. 相似文献
18.
Florian S. Tschernuth Lukas Bichlmaier Sebastian Stigler Prof. Dr. Shigeyoshi Inoue 《欧洲无机化学杂志》2023,26(31):e202300388
The emerging field of Lewis acidic silanes demonstrates the versability of molecular silicon compounds for catalytic applications. Nevertheless, when compared to the multifunctional boron Lewis acid B(C6F5)3, silicon derivatives still lack in terms of reactivity. In this regard, we demonstrate the installation of perfluorotolyl groups (TolF) on neutral silicon atoms to obtain the respective tetra- and trisubstituted silanes Si(TolF)4 and HSi(TolF)3. These compounds were fully characterized including SC-XRD analysis but unexpectedly showed no significant Lewis acidity. By using strongly electron-withdrawing perfluorocresolato groups (OTolF) the tetrasubstituted silane Si(OTolF)4 was obtained, bearing an 8 % increased Δδ(31P) shift when applying the Gutmann-Beckett method, compared to literature-known Si(OPhF)4. Ultimately the heteroleptic Si(PhF)2pinF was successfully synthesized and fully characterized including SC-XRD analysis, introducing a highly Lewis acidic silicon atom holding two silicon-carbon bonds. 相似文献
19.
Damien Mahaut Dr. Aurélien Chardon Loïc Mineur Prof. Guillaume Berionni Prof. Benoît Champagne 《Chemphyschem》2021,22(19):1958-1966
The activation or heterolytic splitting of methane, a challenging substrate usually restricted to transition metals, has so far proven elusive in experimental frustrated Lewis pair (FLP) chemistry. In this article, we demonstrate, using density functional theory (DFT), that 1-aza-9-boratriptycene is a conceptually simple intramolecular FLP for the activation of methane. Systematic comparison with other FLP systems allows to gain insight into their reactivity with methane. The thermodynamics and kinetics of methane activation are interpreted by referring to the analysis of the natural charges and by employing the distortion-interaction/activation strain (DIAS) model. These showed that the nature of the Lewis base influences the selectivity over the reaction pathway, with N Lewis bases favoring the deprotonation mechanism and P bases the hydride abstraction one. The lower barrier of activation for 1-aza-9-boratriptycene and the higher products stability are due to a better interaction energy than its counterparts, itself due to electrostatic interactions with the methane moiety, favorable orbital overlaps allowed by the side-attack, and space proximity between the B and N atoms. 相似文献
20.
Xinyu Tian Jiaxiang Guo Wenting Sun Liuzhong Yuan Prof. Dr. Chuandong Dou Prof. Dr. Yue Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(17):e202200045
Tuning diradical character is an important topic for organic diradicaloids. Herein, we report the precise borylation enabling structural isomerism as an effective strategy to modulate diradical character and thereby properties of organic diradicaloids. We synthesized a new B-containing polycyclic hydrocarbon that has the indeno[1,2-b]fluorene π-skeleton with the β-carbons bonding to two boron atoms. Detailed theoretical and experimental results show that this bonding pattern leads to its distinctive electronic structures and properties in comparison to that of its isomeric molecule. This molecule has the efficient conjugation between boron atoms and π-skeleton, resulting in downshifted LUMO and HOMO levels. Moreover, it exhibits smaller diradical character and thereby inhibited diradical properties, such as significantly blue-shifted light absorption, larger energy bandgap and weak para-magnetic resonance. Notably, this B-containing polycyclic hydrocarbon possesses much stronger Lewis acidity and its Lewis acid-base adducts display enhanced diradical character, demonstrating the positive effects of Lewis coordination on modulating diradical performance. 相似文献