Boron Halides Research Articles

Anchoring of boron halides BX (X: F, Cl, and Br) on transition metal (M: Cr, Mo, W) carbonyl complexes M(CO)5 (M: Cr, Mo, W): structure, bonding, and energy decomposition studies based on theoretical calculations

Anchoring of boron halides BX (X: F, Cl, and Br) on transition metal (M: Cr, Mo, W) carbonyl complexes M(CO)5 (M: Cr, Mo, W): structure, bonding, and energy decomposition studies based on theoretical calculations

Arylboronic Acid Pinacol Esters as Stable Boron Sources for Dihydrodibenzoborepin Derivatives and a Dibenzoborole.

The general synthesis of boron-containing cyclic compounds (boracycles) necessitates toxic organotin precursors or highly reactive boron halides. Here, we report the synthesis of seven- and five-membered boracycles utilizing arylboronic acid pinacol esters (ArBpins) as stable boron sources. Grignard reagents generated from 2,2'-dibromodibenzyl or 2,2'-dibromobiphenyl reacted with ArBpins, where Ar = 9-anthryl (Anth), 2,4,6-trimethylphenyl (Mes), or 2,4,6-triisopropylphenyl (Tip), to give 10,11-dihydro-5H-dibenzo[b,f]borepins or dibenzoborole derivatives. This Bpin-based method was successfully applied to a one-shot double boracycle formation, providing a dihydrodibenzoborepin-anthracene-dihydrodibenzoborepin triad molecule in a good yield. The dihydrodibenzoborepin bearing the Anth group was directly converted to the unsaturated borepin by NBS/AIBN. All products were characterized by NMR, HRMS, and in some cases, single-crystal X-ray diffraction analysis. Additionally, the photophysical properties of the products are also reported.

One-pot synthesis of spiro[adamantane-2,2′-boriranes] via the Cp2TiCl2-catalyzed cycloboration of methyleneadamantane with boron halides

One-pot synthesis of spiro[adamantane-2,2′-boriranes] via the Cp2TiCl2-catalyzed cycloboration of methyleneadamantane with boron halides

Dispersion, Rehybridization, and Pentacoordination: Keys to Understand Clustering of Boron and Aluminum Hydrides and Halides.

The structure, stability, and bonding characteristics of dimers and trimers involving BX3 and AlX3 (X = H, F, Cl) in the gas phase, many of them explored for the first time, were investigated using different DFT (B3LYP, B3LYP/D3BJ, and M06-2X) and ab initio (MP2 and G4) methods together with different energy decomposition formalisms, namely, many-body interaction-energy and localized molecular orbital energy decomposition analysis. The electron density of the clusters investigated was analyzed with QTAIM, electron localization function, NCIPLOT, and adaptive natural density partitioning approaches. Our results for triel hydride dimers and Al2X6 (X = F, Cl) clusters are in good agreement with previous studies in the literature, but in contrast with the general accepted idea that B2F6 and B2Cl6 do not exist, we have found that they are predicted to be weakly bound systems if dispersion interactions are conveniently accounted for in the theoretical schemes used. Dispersion interactions are also dominant in both homo- and heterotrimers involving boron halide monomers. Surprisingly, B3F9 and B3Cl9 C3v cyclic trimers, in spite of exhibiting rather strong B-X (X = F, Cl) interactions, were found to be unstable with respect to the isolated monomers due to the high energetic cost of the rehybridization of the B atom, which is larger than the two- and three-body stabilization contributions when the cyclic is formed. Another important feature is the enhanced stability of both homo- and heterotrimers in which Al is the central atom because Al is systematically pentacoordinated, whereas this is not the case when the central atom is B, which is only tri- or tetra-coordinated.

Reactivity of Silylene with Gallium- and Boron Trihalide at Reductive Conditions Resulting in Unforeseen Products.

Herein, we report a one-pot reaction of gallium and boron halides with potassium graphite in the presence of benzamidinate stabilized silylene LSi-R, (L=PhC(Nt Bu)2 ). The reaction of LSiCl with an equivalent amount of GaI3 in the presence of KC8 leads to the direct substitution of one chloride group by gallium diiodide simultaneously additional coordination of silylene resulted in L(Cl)Si→GaI2 -Si(L)→GaI3 (1). In compound 1, the structure comprises two differently coordinated gallium atoms where one gallium presents between two silylenes and the other gallium is only coordinated by one silylene. In this Lewis acid-base reaction the oxidation states of the starting materials remain unchanged. The same is valid in the silylene boron adduct formation of L(t Bu)Si-BPhCl2 (2) and L(t Bu)Si-BBr3 (3). This new route provides access to galliumhalosilanes challenging to synthesize by any other method.

The mechanism of the replacement of aluminum atoms in 1-ethyl-3-alkylalumolanes by boron atoms with boron halides.

In this study, the mechanism of the replacement reaction of an aluminum atom by a boron atom in the 1-ethyl-3-substituted alumolanes with boron halides is proposed. Theoretical and experimental justifications based on the DFT quantum chemical calculations of the energy parameters of possible reaction routes coupled with monitoring of the reaction between 1-ethyl-3-butylalumolane and BF3·Et2O, BCl3 and BBr3 using 1H, 13C, 11B and 27Al NMR spectroscopy are provided.

A planar per-borylated digermene.

A tetraboryl digermene synthesized by the reaction between a dianionic digermanide nucleophile and a boron halide electrophile is dimeric both in the solid state and in hydrocarbon solution. It features both a planar 'alkene-like' geometry for the Ge2B4 core, and an exceptionally short GeGe double bond. These structural features are consistent with the known electronic properties of the boryl group, and with lowest energy (in silico) fragmentation into two triplet bis(boryl)germylene fragments.

Lewis Acidity Trend of Boron and Aluminium Trihalides: If Not π Back-Bonding, What Else?

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.

Borocyclic Radicals Prepared from Orthoquinone-Containing Polycyclic Aromatics by Photoirradiation

Borocyclic radicals with highly conjugated aromatics were generated from orthoquinone-containing polycyclic aromatic compounds by trapping the photoinduced triplet state with simple boron halide under irradiation with light of appropriate wavelength. The picene-based borocyclic radical was remarkably stable when stored at 23 °C in a desiccator for over 1 year. The crystal structure of this stable radical had a stacking structure of a planar π-conjugated system, and the electrical conductivity was higher than those of ordinary organic radical systems.

α,ω-Dienes in Cp2TiCl2-catalyzed synthesis of boriranes

The Cp2TiCl2-catalyzed cycloboration of α,ω-dienes with boron halides BX3 (X = F and Cl) or RBCl2 (R = Et and n-Pent) in the presence of metallic Mg to obtain 1,2-disubstituted boriranes is reported. The α,ω-dichloroborane reacts with α-olefins under the same reaction conditions to form mono-boriranes linked by a hydrocarbon chain with oxaborinane ring.

Functionalization of N2 via Formal 1,3-Haloboration of a Tungsten(0) σ-Dinitrogen Complex.

Boron tribromide and aryldihaloboranes were found to undergo 1,3‐haloboration across one W−N≡N moiety of a group 6 end‐on dinitrogen complex (i.e. trans‐[W(N2)2(dppe)2]). The N‐borylated products consist of a reduced diazenido unit sandwiched between a WII center and a trivalent boron substituent (W−N=N−BXAr), and have all been fully characterized by NMR and IR spectroscopy, elemental analysis, and single‐crystal X‐ray diffraction. Both the terminal N atom and boron center in the W−N=N−BXAr unit can be further derivatized using electrophiles and nucleophiles/Lewis bases, respectively. This mild reduction and functionalization of a weakly activated N2 ligand with boron halides is unprecedented, and hints at the possibility of generating value‐added nitrogen compounds directly from molecular dinitrogen.

Correction to: Laser Induced Dielectric Breakdown for Chemical Vapor Deposition by Hydrogen Reduction of Volatile Boron Halides BCl3 and BF3

The original version of this article unfortunately contained a mistake in the abstract section and figure 7. The corrections are listed below.

Gas Technique of Simultaneous Borocarburizing of Armco Iron Using Trimethyl Borate

The gas boriding process is an appropriate technique used for increasing the hardness and wear resistance of iron and steels. However, the boron halides (e.g., BCl3, BF3) are rarely used as a boron source during gas boriding in industry due to the toxic character of these reagents. The possibility of the use of organic compounds as a boron source in plasma assisted processes was the instigation to determine the possibility of applying these agents for gas boriding. In the present work trimethyl borate was used as an organic boron source. The use of a N2–H2–B(CH3O)3 atmosphere ensured the appropriate conditions for the simultaneous gas borocarburizing of Armco iron. The process was carried out at 1223 K (950 °C) for 2 h. The produced layer consisted of two zones: an outer zone containing a diffusion of boron atoms and an inner zone containing a diffusion of carbon atoms, under the outer zone. Due to the reduction of trimethyl borate with hydrogen, free atoms of carbon were released for the gas atmosphere. Therefore, there existed favorable conditions for carburizing. Unfortunately, the formation of a carburized layer was the reason for the difficult diffusion of boron atoms. As a consequence, the boron diffusion front was hindered, and the outer boride layer was relatively thin (ca. 7.8 µm). The boride layer contained only Fe2B phase, which was characterized by high hardness in the range from 1103 HV0.01 to 1546 HV0.01. The presence of iron borides in the outer layer was also the reason for increased wear resistance in comparison with untreated Armco iron.

Laser Induced Dielectric Breakdown for Chemical Vapor Deposition by Hydrogen Reduction of Volatile Boron Halides BCl3 and BF3

A possibility of deposition from laser-induced plasma is investigated in search for an economic and simple method for obtaining isotopic compounds from enriched gaseous precursors although no isotopic compounds are used in this the proof-of-principle work. A breakdown in mixtures of BCl3 and BCl3 with hydrogen, argon, and methane are studied both theoretically and experimentally. Equilibrium chemistry calculations show the deposition of boron, boron carbide, and carbon is thermodynamically favorable in BCl3 systems and only carbon in BF3 systems. Dynamic calculation of expanding plasma is performed using fluid dynamics coupled with equilibrium chemistry. Condensed phases of boron, boron carbide, and graphite are predicted with maximum concentrations in peripheral zones of the plasma. In experiment, plasma is induced in mixtures BCl3, H2 + BCl3, H2 + Ar + BCl3, H2 + BCl3 + CH4, BF3, H2 + BF3, H2 + Ar + BF3, and H2 + Ar + BF3. The gases are analyzed before, during, and after laser irradiation by optical and mass spectrometry methods. The results show the composition of reaction products close to that predicted theoretically. The conversion of precursor gases BCl3 and BF3 into gaseous and condensed products is 100% for BCl3 and 80% for BF3. Solid deposits of up to 30 mg are obtained from all reaction mixtures. Due to technical reasons only FTIR characterization of the BCl3 + H2 + CH4 deposit is done. It points to presence of condensed boron and boron carbide predicted by the model. Overall, the calculations and preliminary experimental results imply the chemical vapor deposition with laser induced plasma is promising for conversion of gaseous enriched precursors into elemental isotopes and their isotopic compounds.

Hexahalodiborate Dianions: A New Family of Binary Boron Halides.

The electron‐precise binary boron subhalide species [B2X6]2− X=F, Br, I) were synthesized and their structures confirmed by X‐ray crystallography. The existence of the previously claimed [B2Cl6]2−, which had been questioned, was also confirmed by X‐ray crystallography. The dianions are isoelectronic to hexahaloethanes, are subhalide analogues of the well‐known tetrahaloborate anions (BX4 −), and are rare examples of molecular electron‐precise binary boron species beyond B2X4, BX3, and [BX4]−.

Mild Ring‐Opening 1,3‐Hydroborations of Non‐Activated Cyclopropanes

AbstractThe Brown hydroboration reaction, first reported in 1957, is the addition of B−H across an olefin in an anti‐Markovnikov fashion. Here, we solved a long‐standing problem on mild 1,3‐hydroborations of non‐activated cyclopropanes. A three‐component system including cyclopropanes, boron halides, and hydrosilanes has been developed for borylative ring‐opening of cyclopropanes following the anti‐Markovnikov rule, under mild reaction conditions. Density functional theory (M06‐2X) calculations show that the preferred pathway involves a cationic boron intermediate which is quenched by hydride transfer from the silane.

Mild Ring-Opening 1,3-Hydroborations of Non-Activated Cyclopropanes.

The Brown hydroboration reaction, first reported in 1957, is the addition of B-H across an olefin in an anti-Markovnikov fashion. Here, we solved a long-standing problem on mild 1,3-hydroborations of non-activated cyclopropanes. A three-component system including cyclopropanes, boron halides, and hydrosilanes has been developed for borylative ring-opening of cyclopropanes following the anti-Markovnikov rule, under mild reaction conditions. Density functional theory (M06-2X) calculations show that the preferred pathway involves a cationic boron intermediate which is quenched by hydride transfer from the silane.

Novel Palladium‐Catalyzed Intramolecular Addition of Aryl Bromides to Aldehydes as Key to the Synthesis of 3,3‐Dimethylchroman‐4‐ones and 3,3‐Dimethylchroman‐4‐ols

AbstractMany benzofused cyclic chiral alcohols are biologically active and a variety of synthetic methods has been developed to access these structures. Palladium‐catalyzed intramolecular nucleophilic addition reactions of aryl boron and aryl halide compounds to carbonyls are useful, but control over the cyclization to give a single product has to‐date proven challenging. Here, we describe the first controlled intramolecular nucleophilic addition of aryl bromides to aldehydes, providing the corresponding cycloalkanol or cyclic ketone derivatives simply by changing the base or the ligand. Ten new 3,3‐dimethylchroman‐4‐ol derivatives and six new 3,3‐dimethylchroman‐4‐ones were prepared (with up to 91% conversion and 46% ee).

The Recycling of Spent Ammonia Borane with HBr/AlBr3 and Other HX/AlX3 -Based Schemes.

Although the development and application of a BNHx -waste recycling process is one of the major prerequisites for the use of ammonia borane as hydrogen source material, most research groups in the field have focused on AB hydrogen release and only few groups have worked on the development of energetically viable recycling schemes. In our work we target the development of a closed recycling process containing three desired steps: superacid break-up of the BNHx -waste, catalytic hydrodehalogenation of the generated boron halide, and base-exchange between Et3 NBH3 and ammonia. Catalytic hydrodehalogenation provides a convenient means to generate B-H bonds using molecular hydrogen, avoiding potentially energetically expensive reduction reagents.

Separation of boron isotopes by chemical exchange in liquid-liquid systems

The currently used technologies for the production of boron isotopes for nuclear power and nuclear medicine are based on the application of toxic boron halides. The report is devoted to alternative processes for enrichment of 10B and 11B by chemical exchange in extraction systems using boric acid, that is, without of boron halides. The results of studying phase and isotope equilibrium in two liquid-liquid systems are considered: an aqueous solution of boric acid – an organic phase in the form of tributyl phosphate or a solution of trioctylamine in o-xylene. The obtained values of the separation factor for boron isotopes characterize the predominantly phase isotope effect in the first system, and in the second system the effect of chemical isotope exchange. Accordingly, the values of the single stage separation factor are 1.0067 ± 0.0035 and 1.025 ± 0.005 and are close to similar values for rectification of boron trifluoride and chemical exchange in the anisole process of boron isotope separation. The practical use of the studied extraction systems may allow the separation of boron isotopes in the horizontal cascades of centrifugal extractors in the absence of an environmental hazard.