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Erhardt S Frenking G Chen Z von Ragué Schleyer P 《Angewandte Chemie (International ed. in English)》2005,44(7):1078-1082
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Yang Zheng Jiao Xiong Yangyang Sun Prof. Dr. Xiaobo Pan Prof. Dr. Jincai Wu 《Angewandte Chemie (International ed. in English)》2015,54(44):12933-12936
Stepwise reduction of 9,10‐bis(dimesitylboryl)anthracene afforded an radical anion and a dianion, accompanied by stepwise changes of the aromaticity of the anthracene moiety. The radical has a planar semiquinoidal structure, while the dianion has a puckered quinoidal structure. The alteration of the geometries of the 9,10‐bis(dimesitylboryl)anthracene upon reduction is rationalized by the nature of the bonding. These results have been confirmed by cyclic voltammetry, X‐ray crystallography, NMR, EPR, and UV‐vis‐NIR spectroscopy, as well as DFT calculations. 相似文献
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Sahin Y Präsang C Hofmann M Geiseler G Massa W Berndt A 《Angewandte Chemie (International ed. in English)》2005,44(11):1643-1646
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Dr. Miłosz Pawlicki Mateusz Garbicz Dr. Ludmiła Szterenberg Prof. Lechosław Latos‐Grażyński 《Angewandte Chemie (International ed. in English)》2015,54(6):1906-1909
An understanding of fundamental aspects of archetypal organic structural motifs remains a key issue faced by the experimental and theoretical chemists. Two possible bonding modes for a disubstituted benzene ring, that is a meta and para, determines the π delocalization for oligomeric structures. When the less abundant ortho‐substituted variant is introduced into a triphyrin(2.1.1) skeleton an aromatic molecule is obtained and the carbocyclic ring participates in the conjugation of the macrocycle. The two‐electron reduction and introduction of boron(III) changes the aromatic character and results in an anti‐aromatic structure which has been confirmed by single‐crystal analysis and supported by theoretical calculations. 相似文献
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The electronic structure and bonding situation in 21 metallabenzenes (metal=Os, Ru, Ir, Rh, Pt, and Pd) were investigated at the DFT level (BP86/TZ2P) by using an energy decomposition analysis (EDA) of the interaction energy between various fragments. The aim of the work is to estimate the strength of the pi bonding and the aromatic character of the metallacyclic compounds. Analysis of the electronic structure shows that the metallacyclic moiety has five occupied pi orbitals, two with b1 symmetry and three with a2 symmetry, which describe the pi-bonding interactions. The metallabenzenes are thus 10 pi-electron systems. This holds for 16-electron and for 18-electron complexes. The pi bonding in the metallabenzenes results mainly from the b1 contribution, but the a2 contribution is not negligible. Comparison of the pi-bonding strength in the metallacyclic compounds with acylic reference molecules indicates that metallabenzenes should be considered as aromatic compounds whose extra stabilization due to aromatic conjugation is weaker than in benzene. The calculated aromatic stabilization energies (ASEs) are between 8.7 kcal mol(-1) for 13 and 37.6 kcal mol(-1) for 16 which is nearly as aromatic as benzene (ASE=42.5 kcal mol(-1)). The classical metallabenzene model compounds 1 and 4 exhibit intermediate aromaticity with ASE values of 33.4 and 17.6 kcal mol(-1). The greater stability of the 5d complexes compared with the 4d species appears not to be related to the strength of pi conjugation. From the data reported here there is no apparent trend or pattern which indicates a correlation between aromatic stabilization and particular ligands, metals, coordination numbers or charge. The lower metal-C5H5 binding energy of the 4d complexes correlates rather with weaker sigma-orbital interactions. 相似文献
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The bowl‐shaped C6v B36 cluster with a central hexagon hole is considered an ideal molecular model for low‐dimensional boron‐based nanosystems. Owing to the electron deficiency of boron, chemical bonding in the B36 cluster is intriguing, complicated, and has remained elusive despite a couple of papers in the literature. Herein, a bonding analysis is given through canonical molecular orbitals (CMOs) and adaptive natural density partitioning (AdNDP), further aided by natural bond orbital (NBO) analysis and orbital composition calculations. The concerted computational data establish the idea of concentric double π aromaticity for the B36 cluster, with inner 6π and outer 18π electron counting, which both conform to the (4n+2) Hückel rule. The updated bonding picture differs from existing knowledge of the system. A refined bonding model is also proposed for coronene, of which the B36 cluster is an inorganic analogue. It is further shown that concentric double π aromaticity in the B36 cluster is retained and spatially fixed, irrespective of the migration of the hexagonal hole; the latter process changes the system energetically. The hexagonal hole is a destabilizing factor for σ/π CMOs. The central hexagon hole affects substantially fewer CMOs, thus making the bowl‐shaped C6v B36 cluster the global minimum. 相似文献
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Density functional theory investigations indicate that carbon boronyls (CBO)n (n = 3-7) are considerably more stable in thermodynamics than their boron carbonyl isomers (BCO)n and exhibit aromaticity throughout the whole series. The extra stabilities of (CBO)n originate from their frontier pi molecular orbitals delocalized over the Dnh Cn central rings which are absent in (BCO)n. It is expected that experimental characterization of these (CBO)n species may open a new branch of chemistry on carbon boronyls. 相似文献
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Dr. Kerstin Freitag Dr. Christian Gemel Dr. Paul Jerabek Prof. Dr. Iris M. Oppel Dr. Rüdiger W. Seidel Prof. Dr. Gernot Frenking Hung Banh Katharina Dilchert Prof. Dr. Roland A. Fischer 《Angewandte Chemie (International ed. in English)》2015,54(14):4370-4374
The triangular clusters [Zn3Cp*3]+ and [Zn2CuCp*3] were obtained by addition of the in situ generated, electrophilic, and isolobal species [ZnCp*]+ and [CuCp*] to Carmona’s compound, [Cp*Zn? ZnCp*], without splitting the Zn? Zn bond. The choice of non‐coordinating fluoroaromatic solvents was crucial. The bonding situations of the all‐hydrocarbon‐ligand‐protected clusters were investigated by quantum chemical calculations revealing a high degree of σ‐aromaticity similar to the triatomic hydrogen ion [H3]+. The new species serve as molecular building units of CunZnm nanobrass clusters as indicated by LIFDI mass spectrometry. 相似文献
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Prof. Dr. Gabriel Merino Prof. Dr. Thomas Heine 《Angewandte Chemie (International ed. in English)》2012,51(41):10226-10227
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The most stable form of a B36 cluster has a central hexagonal hole. Such an interesting finding has led to the possible synthesis of a 2D boron sheet by employing the B36 cluster as the building unit. Herein, a DFT study to investigate the reason for the central location of the hexagonal hole in the B36 cluster is presented. The results show that the B36 cluster with a central hexagonal hole is highly thermodynamically and kinetically stable. More importantly, such high stability is further understood through chemical bonding analysis. 相似文献
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Dr. Qiao-Qiao Yan Dr. XiaoYun Zhao Ting Zhang Prof. Dr. Si-Dian Li 《Chemphyschem》2023,24(9):e202200947
Planar, tubular, cage-like, and bilayer boron clusters Bn+/0/− (n=3∼48) have been observed in joint experimental and theoretical investigations in the past two decades. Based on extensive global searches augmented with first-principles theory calculations, we predict herein the smallest perfect core-shell octahedral borospherene Oh B@B38+ ( 1 ) and its endohedral metallo-borospherene analogs Oh Be@B38 ( 2 ), and Oh Zn@B38 ( 3 ) which, with an octa-coordinate B, Be or Zn atom located exactly at the center, turn out to be the well-defined global minima of the systems highly stable both thermodynamically and dynamically. B@B38+ ( 1 ) represents the first boron-containing molecule reported to date which contains an octa-coordinate B center covalently coordinated by eight face-capping boron atoms at the corners of a perfect cube in the first coordination sphere. Detailed natural bonding orbital (NBO) and adaptive natural density partitioning (AdNDP) bonding analyses indicate that these high-symmetry core-shell complexes X@B38+/0/− (X=B, Be, Zn) as super-noble gas atoms follow the octet rule in coordination bonding patterns (1S21P6), with one delocalized 9c-2e S-type coordination bond and three delocalized 39c-2e P-type coordination bonds formed between the octa-coordinate X center and its octahedral Oh B38 ligand to effectively stabilize the systems. Their IR, Raman, and UV-Vis spectra are computationally simulated to facilitate their spectroscopic characterizations. 相似文献
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Hans‐Jrg Himmel 《Angewandte Chemie (International ed. in English)》2019,58(34):11600-11617
Electron‐deficient small boron rings are unique in their formation of σ‐ and π‐delocalized electron systems as well as the avoidance of “classical” structures with two‐center‐two‐electron (2c,2e) bonds. These rings are tolerant of several skeletal electron numbers, which makes their redox chemistry highly interesting. In the past few decades, a range of stable compounds have been synthesized with various electron numbers in their B3 and B4 cores. The electronic structures were evaluated by quantum‐chemical calculations. On the other hand, the chemistry of these rings is still very much underdeveloped, being generally limited to the protonation and redox reactions of individual systems. The linkage of several B3 and/or B4 ring systems should give compounds with attractive electronic properties, thus leading the way to novel boron‐based materials. By summarizing important experimental and theoretical results, this Review intends to provide the basis for the exploration of the chemistry of these rings and, in particular, their integration into larger molecular architectures. 相似文献