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The reaction of boroles with organic azides is known to straightforwardly yield 1,2‐azaborinines, which have generated significant interest as benzene bioisosteres. We show that this powerful synthetic pattern extends to a variety of structurally and chemically diverse boron azides, including recently reported diborane(4) azides. This provides a general, powerful borylation method to expand the chemistry of 1,2‐azaborinines. [ABSTRACT FROM AUTHOR]

BICAAC (bicyclic (alkyl)(amino)carbene) as ambiphilic carbene has been utilized to prepare stable neutral tetrahydrodiborane [BICAAC→ ${\to }$ (H2)B−B(H2)← ${\leftarrow }$ BICAAC] and dihydrodiborene [BICAAC→(H)B=B(H) ← ${\leftarrow }$ BICAAC] compounds. The Lewis base stabilized dihydrodiborene is isoelectronic and isolobal to conventional olefins and therefore offers the possibility to explore the formation of π‐complexes with transition metals. Reaction of the diborene with coinage metal salts (CuCl, AgBr and CuI) leads to the formation of π‐diborene metal complexes via η2 side‐on coordination. These are first examples of dihydrodiborene coinage metal complexes. Interestingly, coordination of two CuCl units to the diborene has been observed for the first time with a considerable lengthening of >B=B< and B- ${-}$ CBICAAC bonds manifesting the key role of the BICAAC combined with small steric requirements of hydride substituents in stabilizing these complexes. The energy decomposition analysis (EDA) calculations reveal the interaction between the diborene and Cu(I)/Ag(I) is mainly electrostatic in nature. [ABSTRACT FROM AUTHOR]

Alkali metal borohydrides present a rich source of energy dense materials of boron and hydrogen, however their potential in propellants has been hitherto untapped. Potassium borohydride is a promising fuel with high gravimetric energy density and relatively low sensitivity to air and moisture. Problems arise due to the dehydrogenation of the borohydride on heating with minimal energy release. Common methods to extract both boron and hydrogen by means of borane species involve direct reaction of boron trifluoride species with alkali borohydrides. However, these methods face storage and safety issues due to rapid release of diborane on mixing the reactants. We propose a method of diborane release through controlled release of boron trifluoride by means of a tetrafluoroborate based ionic liquid. The trifluoride is released from the ionic liquid at elevated temperatures and enables safe mixture of the reactants at room temperature. It was found that the reaction between borohydride and boron trifluoride proceeds well above room temperature with potassium borohydride releasing diborane and potassium fluoride. The reaction pathway shows a primary reaction releasing diborane and potassium fluoride and a second less energy efficient step leading to the formation of potassium tetrafluoroborate. A 3D printed propellant formulation was also tested. [ABSTRACT FROM AUTHOR]

Imidazo-fused diazaborines, which serve as intermediary structures somewhat alongside benzene and borazine, had been of particular interest to Dewar and Snyder more than 60 years ago. To this end, Dewar utilised his ' π -complex theory'so as to represent 'borazaros'as a 'quadrivalent' species; however, sadly, modern representations have deviated and leapt into 'trivalent' counterparts. Bonding in boron species has never been straightforward, to such an extent that the orthodox 'ethane' like diborane, i.e., H3B–BH3, which conformed to the paradigmatic rules of molecular structure, in particular, hybridisation and electronegativity, was later evolved to a more realistic '3-centre 2-electron' bonding so as to give the lie to the purported diborane structures of X-ray diffractors. Herein 11B NMR together with IR spectroscopy sheds light on the nature of bonding in borazaros, and 'caged' cyclic oxazaborons so as to reinforce, and reinvigorate the old literature, which could be of interest to both the synthetic, and medicinal chemist alike. [ABSTRACT FROM AUTHOR]

Treatment of [Cp*TiCl3] with [LiBH4 ⋅ THF] followed by thermolysis with [Ph2E2] (E=S or Se) resulted in the formation of classical diborane(6) complexes, [(Cp*Ti)(η4‐B2H4LL′)] (L=C6H4E; L′=C6H5E; 1 a: E=S, 1 b: E=Se), stabilized at titanium template. To the best of our knowledge, they are the first examples of mono‐metallic classical diborane(6) complexes. The bonding analysis and theoretical studies suggest that the stabilization of these diborane(6) species is due to the presence of four bridging ligands in ĸ4‐fashion, where two of them are phenyl thiolates/selenolates that provide more electrons to the electron‐deficient titanium center. Reactions of these diborane(6) species with [M(CO)5 ⋅ THF] (M=Mo, W) led to the cleavage of the electron‐precise B(sp3)−B(sp3) bond that yielded ĸ3‐hydridoborato complexes [(Cp*Ti)(ĸ3‐BH3R)(μ‐EPh)2{M(CO)4}] (2 a–c: R=H, 3 a–c: R=Ph). In an attempt to isolate the Te‐analogue of 1 a–b, a similar reaction was performed; however, the complex was too unstable to be isolated. Interestingly, the treatment of this unstable intermediate with [W(CO)5 ⋅ THF] yielded [(Cp*Ti)(ĸ3‐BH3R)(μ‐TePh)2{W(CO)4}] (2 d: R=H, 3 d: R=Ph) that are analogues of 2 a–c and 3 a–c, respectively. Formation of these species provide indirect evidence for the existence of unstable [(Cp*Ti)(η4‐B2H4LL′)] (L=C6H4Te; L′=C6H5Te; 1 c). [ABSTRACT FROM AUTHOR]

Hydrogen storage in solid‐state materials represents a promising avenue for advancing hydrogen storage technologies, driven by their potential for high efficiency, reduced risk, and cost‐effectiveness. Among the employed materials, magnesium borohydride (Mg(BH4)2) stands out for its exceptional characteristics, with a gravimetric capacity of 14.9 wt% and a volumetric hydrogen density capacity of 146 kg/m3. However, the practical application of Mg(BH4)2 is impeded by challenges such as high desorption temperatures (≥ 270 °C), sluggish kinetics, poor reversibility, and the formation of unexpected byproducts like diborane. To address these limitations, extensive research efforts have been directed towards enhancing the hydrogen storage properties of Mg(BH4)2. Various strategies have been explored, including incorporating catalysts or additives, nanoconfinement of Mg(BH4)2 within porous supports, and modifications involving metal alloys and compositional adjustments. These approaches are actively under investigation for improving the performance of Mg(BH4)2‐based hydrogen storage systems. This review provides a comprehensive survey of recent advancements in Mg(BH4)2 research, focusing on experimental findings related to nanoconfined Mg(BH4)2 and modified thermodynamic processes aimed at enabling hydrogen release at lower temperatures by mitigating sluggish kinetics. Precisely, nanostructuring techniques, catalyst‐mediated nanoconfinement methodologies, and alloy/compositional modifications will be elucidated, highlighting their potential to enhance hydrogen storage properties and overcome existing limitations. Furthermore, this review also discusses the challenges encountered in utilizing Mg(BH4)2 for hydrogen storage applications and offers insights into the prospects of this material. By synthesizing the latest research findings and identifying areas for further exploration, this review aims to contribute to the ongoing efforts toward realizing the full potential of Mg(BH4)2 as a viable solution for hydrogen storage in diverse applications. [ABSTRACT FROM AUTHOR]

First examples of diborane(6) dianions decorated with weakly coordination B(C6F5)3 (BCF) groups and SiEt3+ moieties have been synthesized demonstrating the synthetic potential of the [B2(CN)6]2− dianion. [B2{CNB(C6F5)3}6]2− (1) was isolated as potassium and tetrabutylammonium salt. 1 is a rare example for a weakly coordinating dianion and it was used for the stabilization of the carbocation [Ph3C]+ and the oxonium acid [H(OEt2)2]+. Reaction of [Ph3C]21 with HSiEt3 resulted in the silylated neutral diborane(6) [B2{CNB(C6F5)3}4(CNSiEt3)2] (2) in which two BCF groups have been selectively replaced by SiEt3+ substituents, underscoring the stability and chemical versatility of the [B2(CN)6]2− dianion. The chemical properties and physicochemical data of 1 and 2 provide insight into electronic, coordinating, and steric properties of theses novel diborane(6) compounds. [ABSTRACT FROM AUTHOR]

Main‐group metallomimetics provide a new way to replace transition metal complexes to activate inert small molecules under mild conditions. In this work, the activation mechanisms of CO2, iPrNCO, and iPrNCNiPr by (μ‐Hydrido) diborane anion ([1H]−) have been investigated by density functional theory (DFT) calculations. Two different activation sites, BB versus BH bond of [1H]−, are investigated and compared. The results show that these inert molecules can be activated by [1H]− through cycloadditions under mild conditions. The reactions with iPrNCO and iPrNCNiPr are dynamic and thermodynamic controlling, the obtained products are related not only to the energy barrier but also to the stability of the products. Moreover, the competition for BB/BH bond site activation is directly related to the steric effect of small molecules. CO2, which is without steric hindrance, can only be activated by the BB bond, whereas iPrNCNiPr can only be activated by the BH bond due to the large steric effect. The medium iPrNCO can be activated not only by the BB bond but also by the BH bond. Our study provides theoretical explanations for the reaction activity and chemoselectivity controlling of the title reaction, and displays the potential applications for compounds containing boron‐boron bonds and inert small molecule activation. [ABSTRACT FROM AUTHOR]

Ammonia borane (AB) has been extensively studied as a solid-state hydrogen storage material. On the other hand, its reactivity with CO2 is still unclear, especially in the solid state. By carefully controlling the CO2 pressure and temperature, AB efficiently reduces a large amount of CO2 without solvent or catalyst. 40 mmol of CO2 reacts with one mole of AB at 0.5 MPa and 60 °C. The mechanism was investigated by NMR and DFT calculation. The reaction proceeds through the formation of diammoniate of diborane (DADB) as an intermediate, followed by the reduction and fixation of CO2 with BH4− to give triformatoborohydride ([HB(OCHO)3]−). Aldehyde is then transferred from B to N, yielding formamide as the main final product. The N-formylation of secondary amine can also be achieved without solvent. Finally, the pyrolysis of the product between AB and CO2 produces N-doped amorphous carbon, opening the door to new clean CO2 valorisation pathways. [ABSTRACT FROM AUTHOR]

A catalyst‐free 1,2‐diborylation of aryllithium with tetra(o‐tolyl)diborane(4) has been achieved, giving a series of 1,2‐diborylaryl lithium species in excellent yields under mild reaction conditions, which leads to 1,2‐di(tolyl)borylarenes in 60–91 % yields upon treatment with the hydride‐abstracting reagent. In these transformations, one sp2 C−H of arene is activated and both boryl units are utilized to build two new (sp2)C−B bonds. This represents a new strategy for selective arene diborylation. Density functional theory (DFT) calculations suggest that an aromatic nucleophilic substitution is a key step in the formation of the products. [ABSTRACT FROM AUTHOR]

The selective formation of homonuclear bonds is of key importance in synthetic chemistry. Especially, dehydrocoupling reactions are attractive as ecologically and economically friendly alternatives to established reductive bond forming reactions, since they do not require the use of stoichiometric amounts of a reducing reagent and produce only valuable dihydrogen as by‐product. Here, we report on a metal‐free B−B dehydrocoupling reaction that starts directly from a simple, easily accessible BH3 adduct, providing convenient access to a new nucleophilic dihydridodiborane in excellent yield. The dihydridodiborane in turn activates dihydrogen, allowing to obtain quantitatively the dideuteridodiborane from the dihydridodiborane by D2 activation. On the basis of detailed quantum‐chemical calculations, the mechanism of this unprecedented reaction is elucidated. Some key points that are essential for metal‐free dehydrocoupling are disclosed, paving the way for their systematic evaluation and application. [ABSTRACT FROM AUTHOR]

Despite their apparent simplicity and numerous potential applications, 1,8‐bis(boronic ester) derivatives of naphthalene, 1,8‐C10H6[B(OR)2]2, have remained elusive until today. We now disclose a facile access route to this compound class via alkoholysis of the 1,8‐naphthalenediyl‐bridged diborane(6) 1. In the cases of monotopic MeOH or EtOH, the target compounds 1,8‐C10H6[B(OR)2]2 (R=Me (2), Et (4)) are contaminated with about 10 % of the corresponding mixed boronic ester/anhydride. By using ditopic pinacol (pin) or 1,8‐naphthalenediol (ndl), the formation of the undesired side products is suppressed and 1,8‐C10H6(Bpin)2 (6) can be isolated in 80 % yield (due to solubility issues, the yield of 1,8‐C10H6(Bndl)2 (7) is lower and less reproducible). The bis(boronic ester)s 2, 4, 6, and 7 have been structurally characterized by X‐ray diffraction. 6 has a sterically encumbered, remarkably distorted molecular framework with a torsion angle B−C(ipso)−C'(ipso)−B' of 38.63(9)°. [ABSTRACT FROM AUTHOR]

The implementation of an algorithm for the determination of vibrational state energies based on a many-body expansion within the framework of configuration interaction theory is presented. An efficient evaluation of the increments within this approach is realized by an iterative configuration selection scheme. The new algorithm is characterized by low memory demands and an embarassingly parallel workload. The convergence of the expansion has been studied for a series of small molecules of increasing size, namely, formaldehyde, ketene, ethylene, and diborane. A threshold function has been employed to reduce the number of increments for high orders of the expansion. Benchmark calculations with respect to customary configuration-selective vibrational configuration interaction calculations are provided. [ABSTRACT FROM AUTHOR]

Metal‐free cycloaddition reactions between a diazido‐diborane and alkynes are used to synthesize new ditriazolyl‐diborane molecules, a bis(ferrocenyl‐1,2,3‐triazolyl)‐diborane and a bis(2‐pyridyl‐1,2,3‐triazolyl)‐diborane. Then, the bis(2‐pyridyl‐1,2,3‐triazolyl)‐diborane was used as polydentate ligand for the synthesis of larger architectures. Reaction with ditriflato‐diborane yielded a tetracationic hexaboron compound, and reaction with metal salts yielded dicationic ring compounds with two hexacoordinate metal atoms and two integrated diborane units. [ABSTRACT FROM AUTHOR]

Boron-based materials have been used for hydrogen storage applications owing to their high volumetric and gravimetric hydrogen density. The present study quantum mechanically investigates the electronic structures of three compounds: diborane (DB, B2H6), ammonia borane (AB, H3BNH3) and phosphine borane (PB, H3BPH3). The exploration is facilitated using calculated nuclear magnetic resonance (NMR) chemical shifts, together with outer valence ionisation potentials (IP) and core electron binding energy (CEBE). The findings show a distinct electronic structure for diborane, differing notably from AB and PB, which exhibit certain similarities. Noteworthy dissimilarities are observed in the chemical environments of the bridge hydrogens and terminal hydrogens in diborane, resulting in a substantial chemical shift difference of up to 5.31 ppm. Conversely, in AB and PB, two distinct sets of hydrogens emerge: protic hydrogens (Hp-N and Hp-P) and hydridic hydrogens (Hh-B). This leads to chemical shifts as small as 0.42 ppm in AB and as significant as 3.0 ppm in PB. The absolute isotropic NMR shielding constant (σB) of 11B in DB is 85.40 ppm, in contrast to 126.21 ppm in AB and 151.46 ppm in PB. This discrepancy indicates that boron in PB has the most robust chemical environment among the boranes. This assertion finds support in the calculated CEBE for B 1s of 196.53, 194.01 and 193.93 eV for DB, AB and PB respectively. It is clear that boron in PB is the most reactive atom. Ultimately, understanding the chemical environment of the boranes is pivotal in the context of dehydrogenation processes for boron-based hydrogen storage materials. [ABSTRACT FROM AUTHOR]

The ditriflato‐diborane B2(μ‐hpp)2(OTf)2 (hpp=1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a]pyrimidinate) acts as a stable surrogate of the elusive dication [B2(hpp)2]2+, being both electrophilic (vacant boron p orbitals) and nucleophilic (filled B−B bond orbital). This combination of seemingly contrasting behaviors could be used to develop a metallomimetic diborane chemistry, with Lewis σ‐basic and π‐acidic substrates being bound and reduced at the diborane. Here, we report on a novel reaction type within this general theme, in which double electron transfer from the diboron unit to the boron–bound organic substrate is coupled with halide transfer in the other direction. Novel diborylated dienamines are synthesized in this way. The scope of this unprecedented reaction motif and the reaction pathways are elucidated. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The incorporation of two distinct boryl groups at the same carbon center in organic molecules has attracted growing research interest due to its potential for facilitating controlled, precise synthesis through stepwise dual carbon‐boron bond transformations. Here we report a method to access unsymmetrical 1,1‐diborylalkene (UDBA) stereoselectively via the reaction of readily available alkynes with a neutral sp2−sp3 diboron reagent (NHC)BH2‐Bpin (NHC=N‐heterocyclic carbene). Attributing to the chemically easily distinguishable nature of the sp2 and sp3 boryl moieties, controllable stepwise derivatization of the resultant UDBAs is realized. This process leads to various multifunctionalized olefins and organoborons, such as acylboranes, which are difficult to prepare by other methods. [ABSTRACT FROM AUTHOR]

The synthesis of the first terminal mono‐boryl complexes of nickel, which are not stabilized by a pincer ligand, is reported. The reaction of the nickel bis‐boryl complex cis‐[Ni(iPr2ImMe)2(Bcat)2] 1 (cat=1,2‐O2C6H4) with the small donor ligand PMe3 led to a complete ligand exchange at nickel with reductive elimination of B2cat2 and formation of the bis‐NHC adduct [B2cat2 ⋅ (iPr2ImMe)2] 3 and [Ni(PMe3)4] 2 as the metal‐containing species. Electrophilic attack of MeI on complex 1 or ligand dismutation of 1 with trans‐[Ni(iPr2ImMe)2Br2] led to loss of only one boryl ligand of 1 and afforded the nickel mono‐boryl complexes trans‐[Ni(iPr2ImMe)2(Bcat)Br] 4 a and trans‐[Ni(iPr2ImMe)2(Bcat)I] 4 b. [ABSTRACT FROM AUTHOR]

The defluorinative functionalization of allylic fluorides represents an attractive approach for the preparation of molecules containing a monofluoroalkene core. In that sense, introducing a "boryl nucleophile" is a powerful strategy to obtain polyvalent borylated intermediates as versatile synthetic precursors. To perform this reaction without the use of transition metals, the nucleophilic character of a diborane/fluoride system was exploited in a SN2′ type‐substitution reaction of gem‐difluoropropenes to install a pinacolborane group. The use of HMDS as a silylated additive is necessary to improve the reactivity. A direct oxidation of the intermediate boronates allowed the isolation of the corresponding β‐fluoroallyl alcohols in low to good yields (9–81 %). Other synthetic transformations of a (2‐fluoroallyl)boronate are also illustrated. [ABSTRACT FROM AUTHOR]

Chiral diborane polymerization catalysts with 3,3′-disubstituted binaphthol-backbones are presented. These compounds deliver isotactic poly(propylene oxide) from racemic monomer with isotactoc diad (m) and triad (mm) placements of up to 92% and >80%, respectively. The resulting polyether is well-defined, of high molar mass and semi-crystalline. [ABSTRACT FROM AUTHOR]

The reaction of tetra(o‐tolyl)diborane(4) with organic azides afforded three different compounds, diborylamines, diboryltriazenes, and B2‐hexazenes having a bicyclic B2N6 ring system. The reaction with aryl azides gave diborylamines, while the reaction with 1 equiv. of alkyl azides furnished diboryltriazenes. In the case of the reaction with an excess amount of primary alkyl azide, a new heterocyclic B2‐hexazenes were obtained. The formation of the B2N6 structure could be explained by one general reaction mechanism via the diboryltriazene intermediate according to the control experiments and DFT calculations. The B2‐hexazenes exhibited a strong fluorescence with a remarkably high fluorescent quantum yield of up to 96 %. [ABSTRACT FROM AUTHOR]

This study presents a quantitative estimation of the B–Hb⋯π interaction of diborane with heteroarenes (pyrrole, furan, oxazole, isoxazole, thiophene, thiazole, and isothiazole) and anionic arenes (cyclopentadienyl anion and pentazolate ion). The DFT-D3 method at the B3LYP-D3/6-311++G(d,p) level of theory was exclusively used for geometry optimization and scrutinizing the stability of the complexes. The results indicated the formation of weakly stable complexes with heterocycles and pentazolate ion (ΔE < 6.0 kcal mol−1). The complex formed between diborane and the cyclopentadienyl anion is very stable (ΔE > 12.0 kcal mol−1) with dispersive interaction playing a secondary role. The stability of the complexes suggested from MP2 calculation and other DFT (ωB97X-D and M06-2X) methods is consistent with the results obtained from the DFT-D3 method. The process of complexation is enthalpy driven, except for the complex between diborane and the cyclopentadienyl ion. The spontaneity of the process is mainly governed by the entropy factor. The plot of NCI was used to visualize the non-covalent interaction regions. NBO analysis was also performed to estimate the strength of the donor-acceptor interaction. The asymmetric and symmetric stretching of the B–Hb⋯π vibrational modes and 1H NMR shift in the free diborane and that in the complexes were also analysed. [ABSTRACT FROM AUTHOR]

Many pictures of the bonding of B2H6 have been presented over the past century, starting with a strong effort to force B2H6 to fit the ideas that were current for C2H6 and building to now viewing the molecular orbital model as the basis for a new transferrable concept of a 3-center-2-electron bond that stimulates creation of new chemistry. Even now, though, some would view this special bond more like a protonated double bond. The historical development of the current understanding of bonding in B2H6 is summarized here. [ABSTRACT FROM AUTHOR]

Tetraazatricyclanes containing two boron atoms in the molecular framework were synthesized for the first time via the heterocyclization reaction of tetraamines with tetrakis(dimethylamino)diborane. Tetrakis(dimethylamino)diborane is a new starting reagent in the synthesis of polyheterocyclic compounds that may be of interest as cytotoxic agents. [ABSTRACT FROM AUTHOR]

Molecular β‐diketiminato (BDI) calcium hydride and n‐hexyl derivatives are shown to display contrasting reactivities toward bis(pinacolato)diboron (B2pin2). Whereas the dimeric constitution of the calcium hydride is retained during formation of an unusual diborane(6) dianion, the initially dimeric organocalcium reagent is converted to a calcium diboranate monomer, [(BDI)Ca{pinB‐Bpin(n‐hex)}]. Attempts to effect heterolysis of the B−B bond of this latter species in a manner reminiscent of a previously reported magnesium system were unsuccessful and resulted in either dismutation to the homoleptic β‐diketiminate, [(BDI)2Ca], or, in the case of organic nitriles, the generation of N‐donor adduct derivatives, [(BDI)Ca(NCR){pinB‐Bpin(n‐hex)}] (R=t‐Bu, i‐Pr, o‐tol). This latter reactivity again contrasts with the previously reported behaviour of an analogous magnesium diboranate, observations that are rationalised by density functional theory (DFT) calculations to be effectively a consequence of the larger radius and lower resultant steric congestion, of the third‐row group 2 cation. [ABSTRACT FROM AUTHOR]

Starting with diboranes with two electron‐rich bridging bicyclic guanidinate substituents, we report in this work the rational synthesis of new dicationic symmetrically‐ and unsymmetrically‐substituted diboranes in SN1‐type substitution reactions in which triflato or bromo substituents are replaced by neutral Lewis bases. The scope of such substitution reactions and their rate are analyzed with different pyridine derivatives of variable Lewis basicity. The first substitution step, leading to a monocationic diborane with one anionic substituent (triflate or bromide) and one neutral Lewis base, proceeds much faster than the second substitution step leading to a dicationic diborane with two neutral Lewis bases. The different time scales for the substitution steps could be used to conveniently synthesize in one‐pot reactions several dicationic, unsymmetrically‐substituted diboranes with two different neutral Lewis bases. [ABSTRACT FROM AUTHOR]

The mechanisms of direct deoxygenative borylation of acetone and benzaldehyde with bis(catecholato)diborane (B2cat2) in the solvent N,N‐dimethylacetamide (DMA) are investigated through detailed density functional theory calculations. These calculations show that the isomer 1,2‐B2cat2 in situ generated from 1,1‐B2cat2 induced by DMA is the reactive boron intermediate for the reactions. The addition of the B−B bond of 1,2‐B2cat2 to the C=O bond of acetone or benzaldehyde via a concerted [2σ+2π]‐cycloaddition‐like transition state is the rate‐limiting step for both the triboration reaction of acetone and the monoboration reaction of benzaldehyde. DMA not only acts as the solvent but also promotes the structural isomerization of B2cat2, the deoxygenation of acetone to form the vinyl boronate intermediate and subsequent diboration of vinyl boronate with 1,2‐B2cat2, as well as the protodeboronation of the gem‐diboronate intermediate in the deoxygenative borylation of benzaldehyde. The presented computational results can explain the observed experimental facts and provide insight into the roles of the isomeric 1,2‐B2cat2 and the solvent DMA in related reactions. [ABSTRACT FROM AUTHOR]

Derived from structurally similar precursors, two different azidodiboranes went through distinct aryl migration reactions triggered by different boron‐boron separation distances. Biphenylene based diborane with a shorter boron‐boron distance underwent heterolateral aryl migration to form a seven‐membered azadiborepin, while xanthrene based diborane with a longer boron‐boron distance afforded a stable bis‐azidoborane scaffold. The pyrolysis of such a bis‐azidoborane led to eight‐membered oxazadiborocine through homolateral aryl migration and subsequent [3+2] cycloaddition. Density functional theory (DFT) calculations unveiled that the boron‐boron separation distances were the intrinsic factors for the distinct migrations. [ABSTRACT FROM AUTHOR]

The chiral building block 5-amino-2-hydroxymethyltetrahydropyran 1a has been previously synthesized through a cumbersome 9-step synthesis from tri-O-acetyl-D-glucal, which renders access to nemtabrutinib (2), a BTK inhibitor currently being evaluated for the treatment of various hematologic malignancies, inefficient and wasteful. Herein, we describe the development of a protecting group-free, 2-step synthesis of 1a from Cyrene™, a biorenewable feedstock. The improved synthesis involves a biocatalytic transamination reaction of Cyrene™ to install the desired amine stereocenter in a single step with high diastereoselectivity. The enzymatic reaction is followed by a stereo-retentive reductive acetal opening reaction of the chiral cyrene amine intermediate 3a to furnish 1a. A mechanistic investigation of the acetal opening reaction is also described which uncovered reaction conditions for the sulfolane mediated in situ generation of diborane as the active reductant. The streamlined synthesis of 1a from Cyrene™ reduced the step count from 9 to 2 synthetic steps which resulted in a >27% yield improvement and a significant reduction in the environmental impact of the synthesis. [ABSTRACT FROM AUTHOR]

The B‐nucleophilic 9H‐9‐borafluorene dianion reacts with 9‐chloro‐9‐silafluorene to afford air‐ and moisture‐stable silylborate salts M[Ar2(H)B−Si(H)Ar2] (M[HBSiH], M=Li, Na). Li[HBSiH] and Me3SiCl give the B−pyridine adduct Ar2(py)B−Si(H)Ar2 ((py)BSiH) or the chlorosilane Li[Ar2(H)B−Si(Cl)Ar2] (Li[HBSiCl]) in C6H6‐pyridine or THF. In both cases, the first step is H− abstraction at the B center. The resulting free borane subsequently binds a py or thf ligand. While the py adduct is stable at room temperature, the thf adduct undergoes a 1,2‐H shift via the cyclic B(μ‐H)Si intermediate BHSi, which is afterwards attacked at the Si atom by a Cl− ion to give Li[HBSiCl]. DFT calculations were employed to support the proposed reaction mechanism and to characterize the electronic structure of BHSi. Treatment of Li[HBSiCl] with the N‐heterocyclic carbene IMe introduces the neutral donor at the Si atom and leads to Ar2(H)B−Si(IMe)Ar2 (HBSi(IMe)), a donor‐acceptor‐stabilized silylene. [ABSTRACT FROM AUTHOR]

Electron-rich ditriflato- and dibromido-diborane(4) molecules with bridging guanidinate substituents readily eliminate triflate/bromide to give monocationic diboranes displaying a dual reactivity as Lewis acids and electron donors. In this work, we report unprecedented reaction sequences in which pyrazine derivatives are first coordinated to the diborane. These coordination compounds are intensely coloured due to electronic excitations from an electron in the B-B bond to a pyrazine π* orbital. Then, in a second, separate step, electron transfer is triggered by pyrazine methylation, simply by addition of MeOTf, increasing the acceptor strength of the coordinated pyrazine unit. Moreover, our experiments show that electron transfer could be triggered by reaction with an excess of pyrazine. We applied a selection of pyrazine derivatives and studied various mono- and dicationic pyrazine-diborane complexes to evaluate the scope of this novel metallomimetic diborane reactivity., (© 2025 Wiley‐VCH GmbH.)

The dual reactivity of boron compounds as Lewis acids and electron donors has spurred the development of a metallomimetic chemistry of boron compounds as a topical research theme. In this work we elaborate on the reaction of specially-designed diborane(4) compounds with quinones, as a prime example showing their dual (metallomimetic) chemistry as a Lewis acid and electron donor. The quinone is first coordinated to the diborane and then reduced by intramolecular electron transfer from the B-B bond to a quinone π* orbital. A variety of substitution reactions of the catecholate-diborane reaction product was carried out, leading to new catecholato-diborane compounds and thereby shedding light on the likely mechanisms. Notably, the results disclose the importance of a facile coordination-mode change of the catecholato ligand (end-on to bridging) for substitution reactions and for the diborane-quinone reactions. The results contribute to the further advancement in the use of diboranes with dual reactivity for substrate binding and reduction., (© 2025 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

The introduction of electron‐donating, bridging guanidinate substituents in diborane(4) compounds allows the synthesis of a variety of new cationic diborane(4) compounds. In this work, strategies for the directed synthesis of cationic di‐ and tetraboron compounds are presented, leading to the synthesis and complete characterization of several new compounds with distinct structural motifs, all exhibiting BII atoms directly bound to each other. Hence, we report on tetracationic donor‐acceptor cyclophanes with diboron donor linkers and organic π‐acceptor units, on paddlewheel‐type cationic diboranes, and on unsymmetrically‐substituted monocationic diboranes. [ABSTRACT FROM AUTHOR]

The complexes formed between three molecules where the diboryl units (HBH2BH) replace the C2H2 moiety in benzene (B6H12, C2B4H10, and C4B2H8) and 10 anions (H−, F−, Cl−, Br−, OH−, CCH−, CH3−, CN−, N3−, and CNO−) have been studied using MP2 computational methods with the complete basis set (CBS) extrapolation scheme. The stability of the complexes for a given anion increases with the number of diborane units in the molecules, and these energy values are correlated with the presence of different anions and number of diborane units. The electron density of the complexes has been characterized and analyzed using the quantum theory of atoms in molecules (QTAIM) and electron density shift (EDS) models. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesized an adsorbent (Xylitol-AC) suitable for removing B 2 H 6 in polysilicon production. • The B 2 H 6 adsorption breakthrough time and breakthrough adsorption capacity of Xylitol-AC are 570 min and 8.45 mg·g−1, respectively. • The priority order of impregnation conditions was analyzed by Grey relational analysis method. • The adsorption mechanism of B 2 H 6 by Xylitol-AC: B 2 H 6 reacts with R-OH to generate B(RO) 3 , B-(RO) 4 and H 2. To enhance polysilicon purity by removing diborane (B 2 H 6) impurities from recycled hydrogen (H 2) in the production of polysilicon, a strategy involving the use of an adsorbent developed from activated carbon (AC) impregnated with xylitol was implemented. The adsorption breakthrough time and B₂H₆ breakthrough adsorption capacity for the adsorbent Xylitol-AC, under optimal xylitol impregnation conditions, were determined to be 570 min and 8.45 mg·g−1, respectively. The importance ranking of various impregnation conditions on adsorption characteristics was analyzed through Grey relational analysis (GRA). Analyses such as SEM-EDS, BET, FT-IR, CO₂-TPD, XRD, XPS, and Raman spectroscopy indicated that the presence of abundant –OH groups in Xylitol-AC plays a pivotal role in its effective B₂H 6 adsorption capability. The mechanism for B₂H 6 adsorption by Xylitol-AC involves the interaction between B₂H 6 and –OH groups, resulting in the formation of B(OR) 3 , B-(OR) 4 , and H₂. [ABSTRACT FROM AUTHOR]

In this work we report the first cycloaddition reactions between a diazido diborane(4) and terminal alkynes, providing unique access to bis‐1,2,3‐triazoles connected by a B−B bridge. The catalyst‐free reactions are highly selective, yielding exclusively the thermodynamically disfavored bis‐1,4‐triazoles. The reactions are enabled by the high thermal stability of the diazido‐diborane [B(hpp)(N3)]2 (hpp=1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐α]pyrimidinate). Due to the tetra‐coordinate boron atoms in this reagent, the reactions are tolerant with respect to the introduction of Lewis‐basic groups at the alkyne. The scope and limitations of the new reactions are discussed. [ABSTRACT FROM AUTHOR]

Although Schleyer's computations in 1979 predicted that the ground state of the parent diborirane features a planar‐tetracoordinate carbon atom (anti van't Hoff–Le Bel geometry), this work demonstrates that substitution of C coupled with N‐heterocyclic carbene (NHC) coordination provides access to isolable diborirane derivatives 3 and 4 with van't Hoff–Le Bel geometry. Species 3 and 4 are isoelectronic with cyclopropane and the highly strained B2C rings feature 2c–2e bent σ bonds. Consequently, the B−B and B−C bonds in 3 are cleaved in the presence of hydride, proton, and chalcogens. The former two reactions gave NHC‐coordinated fluorenyldihydridoborane 5 and dichlorofluorenylborane 6, respectively, whereas the latter transformations afforded novel thiaborirane 8 and selenaborirane 9. In addition, transfer hydrogenation of 3 with ammonia borane (H3N⋅BH3) led to the formation of (μ‐hydrido)diborane 7 via selective cleavage of the B−B bond. These reactivities show potential for their future application in organic synthesis. [ABSTRACT FROM AUTHOR]

Three-center two-electron bonds are important for understanding electron-deficient molecules. To examine such a molecule, we produced a diborane(5) anion with a single-bridged structure upon electron bombardment during matrix deposition of Ar containing a small proportion of diborane(6). The diborane(5) anion was destroyed upon photolysis at 180, 220, 385, and 450 nm, but not at 532 nm. Moreover, the possible formation of neutral diborane(5) was observed upon photolysis at 385 and 450 nm, whereas neutral diborane(3) was observed upon photolysis at 180 and 220 nm. The observed line wavenumbers, relative intensities, and isotopic ratios of the diborane(5) anion agreed satisfactorily with those predicted by density functional theory calculations at the B3LYP/aug-cc-pVTZ level of theory. Thus, this method produced the boron hydride anion of interest with few other fragments, which enabled us to clearly identify the IR spectrum of the diborane(5) anion. [ABSTRACT FROM AUTHOR]

The oxidative addition of five diborane(4) derivatives, symmetrical and unsymmetrical, to [Rh(PMe3)3Cl] was studied. Only for the more electron poor diboron derivatives, B2cat2, B2pin2 and catB–Bpin the resulting octahedral bis-boryl complexes [(PMe3)3Rh(boryl)2Cl] were obtained, while for the more electron rich congeners only the equilibrium oxidative addition (catB–Bdmab) or no significant reaction (pinB–Bdmab) was observed (pin = (OCMe2)2, cat = 1,2-O2C6H4, dmab = 1,2-(NMe)2C6H4). By abstraction of the chlorido ligand with NaBArF (BArF = tetrakis-[3,5-bis-(trifluormethyl)-phenyl]-borat) in the presence of a neutral ligand (L = PMe3, MeCN, MeNC) the corresponding cationic octahedral complexes [(PMe3)3Rh(boryl)2L]+ were obtained. All isolated complexes were fully characterised including single crystal X-ray diffraction and heteronuclear, temperature dependent NMR spectroscopy. Whilst the complexes [(PMe3)3Rh(boryl)2Cl] and [(PMe3)3Rh(boryl)2L]+ show many similarities, their detailed structural and spectroscopic properties depend crucially on the properties of both boryl ligands. [ABSTRACT FROM AUTHOR]

The chemistry of dicationic diboranes with two BII atoms that are engaged in direct B−B bonding is by enlarge unexplored, although these molecules have intriguing properties due to their combined Lewis acidic and electron‐donor properties. Unsymmetric dicationic diboranes are extremely rare, but especially attractive due to their polarized B−B bond. In this work we report the directed synthesis of several stable unsymmetric dicationic diboranes by reaction between the electron‐rich ditriflato‐diborane B2(hpp)2(OTf)2 (hpp=1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐α]pyrimidinate) and phosphino‐pyridines, establishing B−N and B−P bonds with the diborane concomitant with triflate elimination. In the case of 2‐((ditertbutylphosphino)methyl)pyridine, the B−N bond is formed instantly, but the B−P bond formation requires (due to steric constraints) several days at ambient conditions for completion, creating an intermediate that could be used for frustrated Lewis pair (FLP)‐like chemistry. Here we test its reaction with an aldehyde, and propose a new type of FLP‐like chemistry. [ABSTRACT FROM AUTHOR]

Stochastic incorporation kinetics can be a limiting factor in the scalability of semiconductor fabrication technologies using atomic-precision techniques. While these technologies have recently been extended from donors to acceptors, the extent to which kinetics will impact single-acceptor incorporation has yet to be assessed. To identify the precursor molecule and dosing conditions that are promising for deterministic incorporation, we develop and apply an atomistic model for the single-acceptor incorporation rates of several recently demonstrated molecules: diborane (B2H6), boron trichloride (BCl3), and aluminum trichloride in both monomer (AlCl3) and dimer forms (Al2Cl6). While all three precursors can realize single-acceptor incorporation, we predict that diborane is unlikely to realize deterministic incorporation, boron trichloride can realize deterministic incorporation with modest heating (50 °C), and aluminum trichloride can realize deterministic incorporation at room temperature. We conclude that both boron and aluminum trichloride are promising precursors for atomic-precision single-acceptor applications, with the potential to enable the reliable production of large arrays of single-atom quantum devices. [ABSTRACT FROM AUTHOR]

Nanocrystalline sp2-BN thin films have been grown on (0001) 4H-SiC substrates at 1030 °C via continuous flow and discontinuous flow-modulated chemical vapor deposition techniques using diborane (B2H6) and ammonia (NH3) as the B and N sources, respectively. The latter technique enabled observations of both the effect of hydrogen purge steps between precursor injections and the length of injection times for B2H6 on the stoichiometry and microstructure of the films. Stoichiometric BN was achieved in all films grown continuously within the N/B gas phase ratio range of 20–200; this was not observed for the discontinuously grown films unless both the B2H6 flow rate and the injection time were minimized. Cross-sectional transmission electron microscopy of films grown both continuously and discontinuously at N/B = 200 and using short B2H6 injection times relative to that of NH3 for the latter process route revealed the initial growth of ∼4 nm thick partially ordered sp2-BN layers. A transition zone then formed containing randomly oriented polycrystalline grains. Excess B incorporated into the discontinuously grown films during long B2H6 injection times resulted in single layer mixtures of amorphous and sp2-BN without any observed ordering. [ABSTRACT FROM AUTHOR]

Reaction of the Ga(I) compound NacNacGa (9) with the diazo compound N2CHSiMe3 affords the nitrilimine compound NacNacGa(N‐NCSiMe3)(CH2SiMe3) (10). Carrying out this reaction in the presence of pyridine does not lead to C−H activation on the transient alkylidene NacNacGa=CHSiMe3 but generates a metallated diazo species NacNacGa(NHN=CHSiMe3)(CN2SiMe3) (13) that further rearranges into the isonitrile compound NacNacGa(NHN=CHSiMe3)(N(NC)SiMe3) (15). Reactions of 10 with the silane H3SiPh and the borane HBcat furnished products of 1,3 addition to the nitrilimine moiety NacNacGa{N(ERn)NCSiMe3}(CH2SiMe3), whereas reaction with the diborane B2cat2 gave the product of formal nitrene insertion into the B−B bond. DFT calculations suggest that the interaction of 9 with N2CHSiMe3 proceeds through intermediate formation of an alkylidene compound that undergoes CH activation with a second molecule of N2CHSiMe3. Insertion into the B−B bond likely proceeds through an initial 1,3‐addition of the diborane, followed by boryl migration to the former nitrene center. [ABSTRACT FROM AUTHOR]

A number of novel alkynyl‐functionalized diarylbis(dimethylamino)diboranes(4) are prepared by salt metathesis, and the appended alkynyl groups are subjected to hydroboration. Their reactions with monohydroboranes lead to discrete boryl‐appended diborane(4) species, while dihydroboranes induce their catenation to oligomeric species, the first known examples of well‐characterized macromolecular species with B−B bonds. The oligomeric species were found to comprise up to ten repeat units and are soluble in common organic solvents. Some of the oligomeric species have good air stability and all were characterized by NMR and vibrational spectroscopy and size‐exclusion chromatography techniques. [ABSTRACT FROM AUTHOR]

A 1,8‐naphthyridine diphosphine (NDP) reacts with boron‐containing Lewis acids to generate complexes featuring a number of different naphthyridine bonding modes. When exposed to diborane B2Br4, NDP underwent self‐deprotonation to afford [NDP‐B2Br3]Br, an unsymmetrical diborane comprised of four fused rings. The reaction of two equivalents of monoborane BBr3 and NDP in a non‐polar solvent provided the simple phosphine‐borane adduct [NDP(BBr3)2], which then underwent intramolecular halide abstraction to furnish the salt [NDP‐BBr2][BBr4], featuring a different coordination mode from that of [NDP‐B2Br3]Br. Direct deprotonation of NDP by KHMDS or PhCH2K generates mono‐ and dipotassium reagents, respectively. The monopotassium reagent reacts with one or half an equivalent of B2(NMe2)2Cl2 to afford NDP‐based diboranes with three or four amino substituents. [ABSTRACT FROM AUTHOR]