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1.
Zusammenfassung Mit Hilfe röntgenographischer Messungen werden die Boride von Vanadin und Niob untersucht, wobei eine neue Phase der ungefähren Zusammensetzung V2B identifiziert wird, welche mit der entsprechenden Nb-Borid-Phase isotyp ist. Dieselbe Kristallart tritt auch im System: Ta–B auf. Die in der Literatur angegebene -Phase im Zweistoff: Nb–B erweist sich als NbO.Im System: V–B–Si wird wie im analogen Mo-System die Existenz einer ternärenT 2-Phase Me5(Si1/3, B2/3)3 nach-gewiesen1; ihre Gitterkonstanten werden ermittelt.Im Schnitt Ta2Si–Ta2B besteht ein geringes Lösungs-vermögen der beiden Phasen ineinander. Durch Zusatz von 20 Mol-% Ta2Si zu Ta2B erhält man die oben erwähnte neue Kristallart.Bei den Borid-Siliziden der Metalle aus der 4a-, 5a- und 6a-Gruppe werden die Stabilitätsbereiche derT 1-,T 2- undD 88-Phasen miteinander verglichen. 相似文献
2.
The interconversions between isomers with the same spin multiplicity of neutral B6 and charged B6 ? and B6 + clusters have been investigated at the B3LYP/6-311+G* level of theory, including determination of the minimum energy pathways with transition states connecting the corresponding reactants and products. In dynamic calculations, 26 isomers were optimized, including 11 novel isomers. In order to further refine the energies, single-point B3LYP/6-311+G(3df) calculations were carried out on the corresponding B3LYP/6-311+G* geometries of all isomers of B6, B6 ? and B6 + and the corresponding isomerization transition states. The stability of each isomer of B6 (singlet and triplet states), B6 ? (doublet state) and B6 + (doublet state) was analyzed from both thermodynamic and dynamic viewpoints. 相似文献
3.
Haokun Li Gan Xu Shuchang Li Yuhao Wu Dr. Zhenpin Lu 《Chemical record (New York, N.Y.)》2023,23(12):e202300238
Electron-precise B−B bonded compounds are valuable reagents in organic syntheses, which can be used as key starting material for the synthesis of functionalized organoboranes. Bis(pinacolato)diborane(4) B2pin2 and its derivatives are among the most studied diboron species. However, their B−B bonds usually need to be activated by transition metal catalysts or bases for further transformations. Recently, many well-designed/reactive electron-precise B−B bonded compounds have been developed, which could facilitate direct reactions with small molecules, unsaturated substrates, and electrophiles. This review highlights the synthesis, structure, and reactivity of neutral and anionic B−B bonded compounds. 相似文献
4.
Yongqiang Xu Dr. Zhigang Ni Yao Xiao Ziwei Chen Dr. Sisi Wang Lizhi Gai Prof. Dr. You-Xuan Zheng Prof. Dr. Zhen Shen Prof. Dr. Hua Lu Prof. Dr. Zijian Guo 《Angewandte Chemie (International ed. in English)》2023,62(8):e202218023
It is essential to create organic compounds that exhibit circularly polarized luminescence (CPL) in the near-infrared (NIR) range. Helicene-type emitters possess appealing chiroptical features, however, such NIR molecules are scarce due to a paucity of synthetic strategies. Herein, we developed a series of helical β-isoindigo-based B−O−B bridged aza-BODIPY analogs that were synthesized conveniently. The reaction of diimino-β-isoindigo with a heteroaromatic amine produced a restricted ligand cavity, which triggered off the generation of a B−O−B bridge. The B−O−B bridge led to distorted conformations that satisfy the helical requirements, resulting in excellent spectroscopic and chiroptical properties. Tunable CPL with the highest luminescence dissymmetry factor (glum) of 1.3×10−3 and a CPL brightness (BCPL=11.5 M−1 cm−1) in the NIR region was achieved. This synthetic approach is expected to offer a new opportunity to chiral chemistry and increase flexibility for chiroptical tuning. 相似文献
5.
Dr. Guoyun Meng Jianping Zhou Dr. Tianyu Huang Hengyi Dai Dr. Xiao Li Xiaoqin Jia Dr. Lu Wang Dr. Dongdong Zhang Prof. Lian Duan 《Angewandte Chemie (International ed. in English)》2023,62(45):e202309923
Fusing condensed aromatics into multi-resonance (MR) frameworks has been an exquisite strategy to modulate the optoelectronic properties, which, however, always sacrifices the small full width at half maxima (FWHM). Herein, we strategically embed B−N/B−O contained heterocycles as fusion locker into classical MR prototypes, which could enlarge the π-extension and alleviate the steric repulsion for an enhanced planar skeleton to suppress the high-frequency stretching/ scissoring vibrations for ultra-narrowband emissions. Sky-blue emitters with extremely small FWHMs of 17–18 nm are thereafter obtained for the targeted emitters, decreased by (1.4–1.9)-fold compared with the prototypes. Benefiting from their high photoluminescence quantum yields of >90 % and fast radiative decay rates of >108 s−1, one of those emitters shows a high maximum external quantum efficiency of 31.9 % in sensitized devices, which remains 25.8 % at a practical luminance of 1,000 cd m−2 with a small FWHM of merely 19 nm. Notably a long operation half-lifetime of 1,278 h is also recorded for the same device, representing one of the longest lifetimes among sky-blue devices based on MR emitters. 相似文献
6.
Torsten Thiess Dr. Soren K. Mellerup Prof. Dr. Holger Braunschweig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(59):13572-13578
A 1,4,2,3-diazadiborinine derivative was found to form Lewis adducts with strong two-electron donors such as N-heterocyclic and cyclic (alkyl)(amino)carbenes. Depending on the donor, some of these Lewis pairs are thermally unstable, converting to sole B,N-embedded products upon gentle heating. The products of these reactions, which have been fully characterized by NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction, were identified as B,N-heterocycles with fused 1,5,2,4-diazadiborepine and 1,4,2-diazaborinine rings. Computational modelling of the reaction mechanism provides insight into the formation of these unique structures, suggesting that a series of B−H, C−N, and B−B bond activation steps are responsible for these “intercalation” reactions between the 1,4,2,3-diazadiborinine and NHCs. 相似文献
7.
M. Sc. Timo Trageser Dr. Michael Bolte Dr. Hans-Wolfram Lerner Prof. Dr. Matthias Wagner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(20):7800-7805
The tetraaryl μ-hydridodiborane(4) anion [ 2 H]− possesses nucleophilic B−B and B−H bonds. Treatment of K[ 2 H] with the electrophilic 9-H-9-borafluorene (HBFlu) furnishes the B3 cluster K[ 3 ], with a triangular boron core linked through two BHB two-electron, three-center bonds and one electron-precise B−B bond, reminiscent of the prominent [B3H8]− anion. Upon heating or prolonged stirring at room temperature, K[ 3 ] rearranges to a slightly more stable isomer K[ 3 a ]. The reaction of M[ 2 H] (M+=Li+, K+) with MeI or Me3SiCl leads to equimolar amounts of 9-R-9-borafluorene and HBFlu (R=Me or Me3Si). Thus, [ 2 H]− behaves as a masked [:BFlu]− nucleophile. The HBFlu by-product was used in situ to establish a tandem substitution-hydroboration reaction: a 1:1 mixture of M[ 2 H] and allyl bromide gave the 1,3-propylene-linked ditopic 9-borafluorene 5 as sole product. M[ 2 H] also participates in unprecedented [4+1] cycloadditions with dienes to furnish dialkyl diaryl spiroborates, M[R2BFlu]. 相似文献
8.
H. P. Baldus Th. Weber R. Blachnik 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):361-364
Abstract The system P4S3?P4Se3?As4S3?As4Se3 was investigated by thermal and X-ray methods. Five regions of solid solubility with different crystal structures were found. All transform at higher temperatures into the plastically-crystalline state with β-P4S3?structure. The substituted species P4-nAsnSmSe3-m (n = 0–4, m = 0–3) are formed in molten mixtures of A4B3?molecules (FIGURE 1). They were identified by HPLC and mass-spectrometric measurements. After long equilibration times P4Se3, As4S3 and As4Se3 decompose peritectoidally into the resp. A4B4?species and an amorphous product. 相似文献
9.
Jie Xu Weihua Qiu Xu Zhang Zhihan Wu Zhen Zhang Dr. Kai Yang Prof. Dr. Qiuling Song 《Angewandte Chemie (International ed. in English)》2023,62(47):e202313388
The direct C−H functionalization of 1,2-benzazaborines, especially asymmetric version, remains a great challenge. Here we report a palladium-catalyzed enantioselective C−H olefination and allylation reactions of 1,2-benzazaborines. This asymmetric approach is a kinetic resolution (KR), providing various C−B axially chiral 2-aryl-1,2-benzazaborines and 3-substituted 2-aryl-1,2-benzazaborines in generally high yields with excellent enantioselectivities (selectivity (S) factor up to 354). The synthetic potential of this reaction is showcased by late-stage modification of complex molecules, scale-up reaction, and applications. 相似文献
10.
Bingbing Wang Xiangyu Zhang Yangmin Cao Long Zou Prof. Dr. Xiaotian Qi Prof. Dr. Qingquan Lu 《Angewandte Chemie (International ed. in English)》2023,62(14):e202218179
This report describes the unprecedented electrooxidation of a solvent (e.g., DMF)-ligated B2cat2 complex, whereby a solvent-stabilized boryl radical is formed via quasi-homolytic cleavage of the B−B bond in a DMF-ligated B2cat2 radical cation. Cyclic voltammetry and density functional theory provide evidence to support this novel B−B bond activation strategy. Furthermore, a strategy for the electrochemical gem-diborylation of gem-bromides via paired electrolysis is developed for the first time, affording a range of versatile gem-diborylalkanes, which are widely used in synthetic society. Notably, this reaction approach is scalable, transition-metal-free, and requires no external activator. 相似文献
11.
Antonio J. LaPorte Jack E. Feldner Jan C. Spies Tom J. Maher Prof. Martin D. Burke 《Angewandte Chemie (International ed. in English)》2023,62(40):e202309566
Multifunctional organoboron compounds increasingly enable the simple generation of complex, Csp3-rich small molecules. The ability of boron-containing functional groups to modify the reactivity of α-radicals has also enabled a myriad of chemical reactions. Boronic esters with vacant p-orbitals have a significant stabilizing effect on α-radicals due to delocalization of spin density into the empty orbital. The effect of coordinatively saturated derivatives, such as N-methyliminodiacetic acid (MIDA) boronates and counterparts, remains less clear. Herein, we demonstrate that coordinatively saturated MIDA and TIDA boronates stabilize secondary alkyl α-radicals via σB-N hyperconjugation in a manner that allows site-selective C−H bromination. DFT calculated radical stabilization energies and spin density maps as well as LED NMR kinetic analysis of photochemical bromination rates of different boronic esters further these findings. This work clarifies that the α-radical stabilizing effect of boronic esters does not only proceed via delocalization of radical character into vacant boron p-orbitals, but that hyperconjugation of tetrahedral boron-containing functional groups and their ligand electron delocalizing ability also play a critical role. These findings establish boron ligands as a useful dial for tuning reactivity at the α-carbon. 相似文献
12.
M. Sc. Thomas Kaese B. Sc. Hendrik Budy Dr. Michael Bolte Dr. Hans-Wolfram Lerner Prof. Dr. Matthias Wagner 《Angewandte Chemie (International ed. in English)》2017,56(26):7546-7550
Deprotonation of the doubly arylene-bridged diborane(6) derivative 1 H2 with (Me3Si)3CLi or (Me3Si)2NK gives the B−B σ-bonded species M[ 1 H] in essentially quantitative yields (THF, room temperature; M=Li, K, arylene=4,4′-di-tert-butyl-2,2′-biphenylylene). With nBuLi as the base, the yield of Li[ 1 H] drops to 20 % and the 1,1-bis(9-borafluorenyl)butane Li[ 2 H] is formed as a side product (30 %). In addition to the 1,1-butanediyl fragment, the two boron atoms of Li[ 2 H] are linked by a μ-H bridge. In the closely related molecule Li[ 3 H], the corresponding μ-H atom can be abstracted with (Me3Si)3CLi to afford the B−B-bonded conjugated base Li2[ 3 ] (THF, 150 °C; 15 %). Li[ 1 H] and Li[ 2 H] were characterized by NMR spectroscopy and X-ray crystallography. 相似文献
13.
Miao Yan Hai-Ru Li Xiao-Yun Zhao Xiao-Qin Lu Yue-Wen Mu Hai-Gang Lu Si-Dian Li 《Journal of computational chemistry》2019,40(9):966-970
Based on detailed bonding analyses on the fluxional behaviors of planar B19−, tubular Ta@B20−, and cage-like B39−, we propose the concept of fluxional bonds in boron nanoclusters as an extension of the classical localized bonds and delocalized bonds in chemistry. © 2018 Wiley Periodicals, Inc. 相似文献
14.
R. Kieffer O. Schob H. Nowotny F. Benesovsky 《Monatshefte für Chemie / Chemical Monthly》1962,93(2):517-521
Zusammenfassung Der Schnitt: Me3Si (Me=Cr, W bzw. Mo, W) wird an Hand heißgepreßter und in Argon homogenisierter Legierungen untersucht; es läßt sich weder das metastabile W3Si, noch eine W-reiche Mischphase von diesem Typ beobachten. Cr3Si nimmt bei 1500°C etwa 20 Mol%, W3Si auf, während Mo3Si selbst bei 1900°C praktisch kein W3Si löst (ev. wenige Mol%). Dagegen bestehen lückenlose Mischreihen zwischen den Me5Si3-Phasen mit W5Si3-Typ. Die grundsätzliche Aufteilung der Phasenfelder ist damit möglich.Mit 2 Abbildungen 相似文献
15.
Jin Xu Yingze Zhang Prof. Jun Liu Prof. Lixiang Wang 《Angewandte Chemie (International ed. in English)》2023,62(42):e202310838
Organic molecules with near-infrared II (NIR II) light absorption are essential for many biological and opto-electronic applications. Herein, we report monodispersed oligomers as NIR II light absorber using a new molecular design strategy of resonant N−B←N unit, i.e. balanced resonant boron-nitrogen covalent bond (B−N) and boron-nitrogen coordination bond (B←N). We synthesize a series of monodispersed oligomers with thiophene-fused 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (TB), which contains resonant N−B←N unit, as the repeating unit. The TB pentamer exhibits the maximum absorption wavelength of 1169 nm, which is the longest for oligomers reported so far. Organic photodetectors (OPDs) with the TB tetramer as the electron acceptor shows the specific detectivity of 2.98×1011 Jones at 1180 nm under zero bias. This performance is among the best for NIR II OPDs. These results indicate a new kind of NIR II absorbing molecules as excellent opto-electronic materials. 相似文献
16.
Jin Xu Prof. Jun Liu Prof. Lixiang Wang 《Angewandte Chemie (International ed. in English)》2023,62(24):e202303870
Since the breakthrough of conductive polymers in 1977, scientists have made great efforts to create small band gap (Eg) conjugated polymers. Two general strategies to design small Eg conjugated polymers are quinoid structure and donor-acceptor structure. Ultrasmall Eg conjugated polymers (Eg<1.0 eV) always suffer from poor air stability because of high-lying HOMO energy levels. In this work, we report a new strategy to design ultrasmall Eg conjugated polymers by N−B←N unit, i.e. balanced resonant boron-nitrogen covalent bond (B−N) and boron-nitrogen coordination bond (B←N). The resulting polymer exhibits an Eg of 0.82 eV and an onset absorption wavelength of >1500 nm. Moreover, the polymer exhibits excellent air stability because of its low-lying LUMO/HOMO energy levels. An unprecedented property of this polymer is the selective light absorption in the infrared range (800–1500 nm) and high transparency in the visible range (400–780 nm). Using this property, for the first time, we demonstrate the application of conjugated polymers as transparent thermal-shielding coating layer on glass, which reduces indoor solar irradiation through window and consequently reduces power consumption for cooling of buildings and cars in summer. 相似文献
17.
Magnetische Messungen an den Teilsystemen TiC−ZrC,TiC−HfC,ZrC−HfC,TiC−VC,TiC−NbC,TiC−TaC und NbC−TaC
Ohne ZusammenfassungMit 3 Abbildungen 相似文献
18.
19.
H. Bittner 《Monatshefte für Chemie / Chemical Monthly》1964,95(6):1514-1520
Ohne ZusammenfassungMit 4 Abbildungen 相似文献
20.
Lu Luo Shuai Tang Jiangyue Wu Shiwei Jin Hua Zhang 《Chemical record (New York, N.Y.)》2023,23(4):e202300023
Aromatic organoboron compounds are highly valuable building blocks in organic chemistry. They were mainly synthesized through aromatic C−H and C−Het borylation, in which transition metal-catalysis dominate. In the past decade, with increasing attention to sustainable chemistry, numerous transition metal-free C−H and C−Het borylation transformations have been developed and emerged as efficient methods towards the synthesis of aromatic organoboron compounds. This account mainly focuses on recent advances in transition metal-free aromatic C−H, C−N, C−S, and C−O borylation transformations and provides insights to where further developments are required. 相似文献