Boron Azides Research Articles

Theoretical Investigation on Structure-Property Relationship of Asymmetric Clusters (CH3FBN3)n (n = 1– 6)

The structural, relative stability, electronic, IR vibrational, and thermodynamic properties of asymmetric clusters (CH3FBN3)n (n = 1–6) are systematically investigated using density functional theory (DFT) method. Results show that clusters (CH3FBN3)n (n = 2–6) form a cyclic structure with a B atom and a Nα atom binding together. Five main characteristic regions are observed and assigned for the calculated IR spectra. The size-dependent second-order energy difference shows that clusters (CH3FBN3)3 and (CH3FBN3)5 have relatively higher stability and enhanced chemical inertness compared with the neighboring clusters. These two clusters may serve as the cluster-assembled materials. The variations of thermodynamic properties with temperature T or cluster size n are analyzed, respectively. Based on enthalpies in the range of 200–800 K, the formations of the most stable clusters (CH3FBN3)n (n = 2–6) from monomer are thermodynamically favorable. These data are helpful to design and synthesize other asymmetric boron azides.

Probing the Structures and Properties of Asymmetric Clusters (CH3ClBN3)n (n = 1–6) with Density Functional Theory

The structures, stabilities, IR spectrum and thermodynamic properties of small asymmetric clusters (CH3ClBN3)n (n = 1–6) are probed using density functional theory (DFT) method. The results indicate that the B and Nα atoms have a tendency to bond together in clusters (CH3ClBN3)n (n = 2–6). The trend of the structures for clusters (CH3ClBN3)n (n = 1–6) with an increase in cluster size n is explored. Based on vibrational analysis, the IR spectra for clusters (CH3ClBN3)n (n = 1–6) are obtained and assigned. The chemical stabilities of the clusters are corroborated from second order difference energy and the binding energies. The influences of temperature T and cluster size n on the thermodynamic properties of clusters are analyzed. According to the enthalpies, the formation of the most stable clusters (CH3ClBN3)n (n = 2–6) from the monomer is thermodynamically favorable at room temperature, which would be helpful for the design and synthesis of asymmetric boron azides.

Cycloaddition reactions of (C6F5)2BN3 with dialkyl acetylenedicarboxylates.

The 1,3-dipolar cycloaddition reactions of the electron deficient boron azide, (C6F5)2BN3 (1) with the electron-poor acetylenes RO2CC≡CCO2R (R = Me, Et) afforded the new mono- and bis-1,2,3-triazole derivatives and .

Boryl azides in 1,3-dipolar cycloadditions.

The 1,3-dipolar cycloaddition reaction of boron azides with alkynes has been investigated experimentally and computationally. At room temperature pinBN3 (pin = pinacolato) reacts with the strained triple bond of cyclooctyne with formation of an oligomeric boryl triazole. Alcoholysis of the oligomer yields the parent 4,5,6,7,8,9-hexahydro-2H-cyclooctatriazole, which could be characterized as a hydrate by X-ray crystallography. A computational analysis of the reaction of tri- and tetracoordinate boron azides R2BN3 (R = H, Me, pin, cat; cat = catecholato) and IMe·H2BN3 (IMe = 2,6-dimethylimidazole-2-ylidene) reveals significant differences in the reactivity depending on the coordination number: tricoordinate boron azides behave as type II 1,3-dipoles, while the tetracoordinate IMe·H2BN3 is an electron-rich 1,3-dipole (type I) that strongly prefers reactions with electron-poor alkynes.

Boron Perturbed Click Reactions Prompt Aromatic CH Activations

AbstractThe reaction of boron alkynes and boron azides leads to rare N3BC heterocycles resulting from aromatic CH activation of benzene and toluene. While subsequent treatment with PMe3 gave the PB adduct with the exocyclic boron, reaction with PtBu3 effected deprotonation of the heterocycle to give the corresponding phosphonium salt.

Boron perturbed click reactions prompt aromatic C-H activations.

The reaction of boron alkynes and boron azides leads to rare N3BC heterocycles resulting from aromatic C-H activation of benzene and toluene. While subsequent treatment with PMe3 gave the P-B adduct with the exocyclic boron, reaction with PtBu3 effected deprotonation of the heterocycle to give the corresponding phosphonium salt.

Boron azides in Staudinger oxidations and cycloadditions

Staudinger reactions of Cy2BN3 with tri-substituted phosphines (R3P) yielded the boron-nitrogen-phosphorus linked systems Cy2BN=PR3 (R = Et, (t)Bu, Cy, Ph) (1a-1d respectively). Similarly, reaction of (C6F5)2BN3 with the phosphines P(t)Bu3, PPh3, Ph2PC≡CPh and Ph2PC≡CPPh2 yielded (C6F5)2BN=PR3 (2a-d respectively). In contrast, the reaction of (C6F5)2BN3 with Ph2P-C≡Cp-tol in the presence of excess Me3SiN3 afforded the bicyclic product 3 [1-(C6F5)2B-4-(p-tol)-1H-1,2,3-triazole-5-P(NH)Ph2] in which both a Staudinger and a cycloaddition reaction has taken place. However, if the Staudinger reaction is prohibited via phosphine oxidation as in the case of (EtO)2P(O)C≡CP(O)(OEt)2 then the unusual dimeric product 4 [2-(C6F5)2B-4-(P(O)OEt2)-2H-1,2,3-triazole-5-P(O)(OEt)(OB(C6F5)2)] is generated. The structures of 1b-d, 2b-d, 3 and 4 have been determined by X-ray diffraction.

Cycloaddition reactions between dicyclohexylboron azide and alkynes

The room temperature 1,3-dipolar cycloaddition reactions of the boron azide, Cy2BN3 with the electron-poor acetylenes RCO2C≡CCO2R, EtC≡CCOMe and HC≡CP(=O)Ph2 afforded new 1,2,3-triazoles. In the case of RCO2C≡CCO2R, a new macrocyclic product was isolated with loss of the R group.

Substitution Reactions at Tetracoordinate Boron: Synthesis of N-Heterocyclic Carbene Boranes with Boron−Heteroatom Bonds

Boryl halide, carboxylate and sulfonate complexes of 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (dipp-Imd-BH(2)X, X = halide or sulfonate) have been prepared from the parent borane dipp-Imd-BH(3) by (1) substitution reactions with R-X (X = halide or sulfonate), (2) reactions with electrophiles (like I(2) or NIS), or (3) acid/base reactions with HX (provided that HX has a pK(a) of about 2 or less). Dipp-Imd-BH(2)I is most conveniently prepared by reaction with diiodine while dipp-Imd-BH(2)OTf is best prepared by reaction with triflic acid. These and other less reactive complexes behave as electrophiles and can be substituted by a wide range of heteroatom nucleophiles including halides, thiolates and other sulfur-based nucleophiles, isocyanate, azide, nitrite, and cyanide. The resulting products are remarkably stable, and many have been characterized by X-ray crystallography. Several are members of very rare classes of functionalized boron compounds (boron azide, nitro compound, nitrous ester, etc.).

Structure, stability and chemical bonding character of covalent boron azides BX(N 3) 2 (X=F, Cl, Br)

Geometrical structures and stability of covalent boron azides BX(N 3) 2 (X=F, Cl, Br), including a previously reported trans BCl(N 3) 2 structure 1 with C s symmetry, were investigated at the B3LYP/6-311+G* level of theory. The optimized cis structures 2 with C 2v symmetry are virtually degenerate to 1 and are more stable than the optimized structures 3 and 4. Analysis of the natural population for the BX(N 3) 2 (X=F, Cl, Br) systems indicates that the central N–N bond in azide groups is intermediate between a single and double bond, the terminal N–N bond trends to be intermediate between a double and triple bond, and the sp 2 hybridization B atom donates an empty p orbital to form a large delocalization π 4 6 bond, which make these covalent boron azides to be more stable.

Synthesis and structural studies on fluorophenylboron azides

The fluorophenyl substituted boron chlorides (R F) 2BCl ( 3 and 4) and dichlorides R FBCl 2 ( 6 and 7) (R F=2,6-F 2C 6H 3, 2-FC 6H 4) were prepared using the stannylated aryl transfer reagents (R F) 2SnMe 2 ( 1 and 2). The boron azides (R F) 2BN 3 ( 8– 9), [2,4,6-(CF 3) 3C 6H 2] 2BN 3 ( 10) and diazides R FB(N 3) 2 ( 11 and 12) were synthesized by the reaction of the corresponding boron chlorides (R F) 2BCl ( 3 and 4), [(CF 3) 3C 6H 2] 2BCl ( 5) and R FBCl 2 ( 6 and 7) with Me 3SiN 3. The influence of the electron withdrawing substituents on the molecular structure of these azides is discussed. The reactions were also performed in the presence of pyridine yielding the adducts (R F) 2BN 3·py and R FB(N 3) 2·py ( 13– 16). All compounds were characterized by multinuclear NMR, vibrational (IR, Raman) spectroscopy; and the molecular structures of 1, 3, 8, 10a ([(CF 3) 3C 6H 2] 2BN 3/[(CF 3) 3C 6H 2] 2BOH) and 14 were established by single crystal X-ray crystallography.

Bis(pentafluorophenyl)boron azide: synthesis and structural characterization of the first dimeric boron azide

Download options Please wait... Supplementary files Crystal data TXT (15K) Article information DOI https://doi.org/10.1039/B001103G Article type Communication Submitted 09 Feb 2000 Accepted 06 Mar 2000 First published 03 Apr 2000 Download Citation Chem. Commun., 2000, 667-668 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Bis(pentafluorophenyl)boron azide: synthesis and structural characterization of the first dimeric boron azide W. Fraenk, T. M. Klapötke, B. Krumm and P. Mayer, Chem. Commun., 2000, 667 DOI: 10.1039/B001103G To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Wolfgang Fraenk Thomas M. Klapötke Burkhard Krumm Peter Mayer

Synthesis and characterization of new azido(o-phenylenedioxy)boranes and azidobicyclononylboranes †

The boron azides azido(o-phenylenedioxy)borane, (1,2-C6H4O2)B(N3) 1, and azidobicyclononylborane, C16H28NB2(N3) 3, have been prepared by the reaction of the corresponding chloroborane with trimethylsilyl azide. Both reactions were also carried out in the presence of pyridine. The resulting donor–acceptor complexes 1·C5H5N 2 and 3·C5H5N 5 and the boron azides (1, 3) have been characterized by analytical and spectroscopic methods. The molecular structures of 1, 3 and 5 have been confirmed by a single crystal X-ray diffraction study. The formation of 3 has been observed by a low temperature 11B NMR study and a probable mechanism is discussed.

Mechanism of the Curtius-type rearrangement in the boron series. An ab initio study of the boryinitrene (H2B–N)–iminoborane (HBNH) isomerisation

Ab initio calculations on the model H2BN to HBNH rearrangement suggest that the Curtius-type thermolysis of boron azide (R2B–N3) yielding iminoborane (RBNR) does not involve the intermediacy of borylnitrene (R2B–N); under photochemical conditions, the later can, however, be formed from the lowest-lying triplet state of azide and does not rearrange to its more stable isomer but undergoes instead typical reactions.

Beiträge zur chemie der borazide IX. Wanderungstendenzen, kinetik und mechanismus der thermischen diorganylborazid-umlagerung

We found the following series of migration aptitudes of organic groups X migrating from the B- to the α-N-atom as a result of the thermal decomposition of boron azides XPhBN 3: ▪ The thermal stability of diorganylboron azides increases according to: ▪ We conclude from the experimental data that diorganylboron azides decompose in a synchronous process with anchimeric assistance by the organic ligands. The anchimeric assistance increases with the electron-attracting forces and the bulky character of the ligands.