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The reactivity of a diruthenium tetrahydride complex towards three selected dihydroboranes was investigated. The use of [DurBH2] (Dur=2,3,5,6‐Me4C6H) and [(Me3Si)2NBH2] led to the formation of bridging borylene complexes of the form [(Cp*RuH)2BR] (Cp*=C5Me5; 1 a: R=Dur; 1 b: R=N(SiMe3)2) through oxidative addition of the B−H bonds with concomitant hydrogen liberation. Employing the more electron‐deficient dihydroborane [3,5‐(CF3)2‐C6H3BH2] led to the formation of an anionic complex bearing a tetraarylated chain of four boron atoms, namely Li(THF)4[(Cp*Ru)2B4H5(3,5‐(CF3)2C6H3)4] (4), through an unusual, incomplete threefold dehydrocoupling process. A comparative theoretical investigation of the bonding in a simplified model of 4 and the analogous complex nido‐[1,2(Cp*Ru)2(μ‐H)B4H9] (I) indicates that there appear to be no classical σ‐bonds between the boron atoms in complex I, whereas in the case of 4 the B4 chain better resembles a network of three B−B σ bonds, the central bond being significantly weaker than the other two. [ABSTRACT FROM AUTHOR]

Crystallizing molecules with long flexible chains is a challenge, making it difficult to perform X‐ray crystallography. Chaperones can assist in the crystallization of compounds that do not crystallize by themselves by producing solvate crystals that contain the analyte in their three‐dimensional lattices. Among the most versatile chaperones for liquid analytes are tetraaryladamantanes (TAAs), but the size of the compounds that can be encapsulated is limited, and attempts to surpass this limit with known TAAs were unsuccessful. Here we report that 1,3,5,7‐tetrakis(2‐fluoro‐4‐methoxyphenyl)adamantane (TFM) is a crystallization chaperone for acyclic molecules up to the molecular weight of phytyl acetate (338 g/mol). Encapsulation of such a large acyclic compound was achieved when the analyte was esterified and when a two‐step temperature protocol was used for crystallization. Exploratory work indicates that a drop to −20 °C allows for encapsulation of squalene (Mr 411 g/mol), albeit with positional disorder of the analyte. Our X‐ray crystal structures of solvates with flexible analytes shed light on how crystalline order can be imposed on large acyclic analytes. The new, fluorinated TAA gives access to crystal structures that were inaccessible thus far. [ABSTRACT FROM AUTHOR]

Crystallizing molecules with long flexible chains is a challenge, making it difficult to perform X‐ray crystallography. Chaperones can assist in the crystallization of compounds that do not crystallize by themselves by producing solvate crystals that contain the analyte in their three‐dimensional lattices. Among the most versatile chaperones for liquid analytes are tetraaryladamantanes (TAAs), but the size of the compounds that can be encapsulated is limited, and attempts to surpass this limit with known TAAs were unsuccessful. Here we report that 1,3,5,7‐tetrakis(2‐fluoro‐4‐methoxyphenyl)adamantane (TFM) is a crystallization chaperone for acyclic molecules up to the molecular weight of phytyl acetate (338 g/mol). Encapsulation of such a large acyclic compound was achieved when the analyte was esterified and when a two‐step temperature protocol was used for crystallization. Exploratory work indicates that a drop to −20 °C allows for encapsulation of squalene (Mr 411 g/mol), albeit with positional disorder of the analyte. Our X‐ray crystal structures of solvates with flexible analytes shed light on how crystalline order can be imposed on large acyclic analytes. The new, fluorinated TAA gives access to crystal structures that were inaccessible thus far. [ABSTRACT FROM AUTHOR]

The steric and electronic properties of aryl substituents in monoaryl borohydrides (Li[ArBH3]) and dihydroboranes were systematically varied and their reactions with [Ru(PCy3)2HCl(H2)] (Cy: cyclohexyl) were studied, resulting in bis(σ)‐borane or terminal borylene complexes of ruthenium. These variations allowed for the investigation of the factors involved in the activation of dihydroboranes in the synthesis of terminal borylene complexes. The complexes were studied by multinuclear NMR spectroscopy, mass spectrometry, X‐ray diffraction analysis, and density functional theory (DFT) calculations. The experimental and computational results suggest that the ortho‐substitution of the aryl groups is necessary for the formation of terminal borylene complexes. [ABSTRACT FROM AUTHOR]

A series of bis(σ)‐borane complexes of Group 6 transition metals were prepared by direct dihydroborane coordination to the metal center. Reaction of [M(CO)3(PCy3)2] and two dihydroboranes [DurBH2] and [(Me3Si)2NBH2] (Dur=2,3,5,6‐Me4C6H) yielded bis(σ)‐borane complexes fac‐[M(CO)3(PCy3){η2‐(H2BR)}] (R=Dur; 1: M=Cr, 2: M=W; R=N(SiMe3)2; 3: M=Cr, 4: M=W). In the case of molybdenum, we have isolated an arene complex (5) with [DurBH2] in which the Dur group acts as a η6‐bound ligand, and with [(Me3Si)2NBH2] a similar bis(σ)‐borane complex was isolated, cis,trans‐[Mo(CO)2(PCy3)2{η2‐(H2BN(SiMe3)2}] (6), with a different pattern of auxiliary ligands. The complexes were investigated by multinuclear NMR spectroscopy, mass spectrometry, X‐ray diffraction analysis, and computational methods. Quantum theory of atoms in molecules (QTAIM) calculations demonstrated that the borane complexes may be described as pure bis(σ)‐borane complexes rather than elongated or stretched examples given that the calculations do not show the presence of a ring‐critical point (RCP) at the ring formed by the interactions of the B−H with metal center. [ABSTRACT FROM AUTHOR]

A series of chiral mechanochromic copper(I) cAAC (cAAC=cyclic (alkyl)(amino)carbene) complexes with a variety of amide ligands have been studied with regard to their photophysical and chiroptical properties to elucidate structure‐property relationships for the design of efficient triplet exciton emitters exhibiting circularly polarized luminescence. Depending on the environment, which determines the excited state energies, either thermally activated delayed fluorescence (TADF) from 1/3LLCT states or phosphorescence from 3LLCT/LC states occurs. However, neither chiral moieties at the carbene nor at the carbazolate ligands provide detectable luminescence dissymmetries glum. An exception is [Cu(phenoxazinyl)(cAAC)], showing orange to deep red TADF with λmax=601–715 nm in solution, powders and in PMMA. In this case, the amide ligand can undergo distortions in the excited state. This design motif leads to the first linear, non‐aggregated CPL‐active copper(I) complex with glum of −3.4 ⋅ 10−3 combined with a high radiative rate constant of 6.7 ⋅ 105 s−1. [ABSTRACT FROM AUTHOR]

A new crystallization chaperone called TFM has been developed, which allows for the formation of X-ray diffraction-based crystal structures of liquid molecules that would otherwise be difficult to obtain. This chaperone acts like a glove that can fit molecules of various sizes, resulting in successful crystallization. The article also introduces a new temperature jump crystallization protocol. The cover graphic of the article displays the chaperone and the crystal lattice of the squalene solvate. [Extracted from the article]

The article discusses a new crystallization chaperone called TFM, which allows for the formation of X-ray diffraction-based crystal structures that would otherwise be impossible to obtain. The chaperone acts like a glove that fits many different sizes, enabling the crystallization of liquid molecules as a solvate. The article also introduces a new temperature jump crystallization protocol. The cover graphic of the article depicts the analytes and the chaperone, along with the crystal lattice of the squalene solvate. [Extracted from the article]

The 2‐aryl‐3,4,5,6‐tetraphenyl‐1,2‐azaborinines 1‐EMe3 and 2‐EMe3 (E=Si, Sn; aryl=Ph (1), Mes (=2,4,6‐trimethylphenyl, 2)) were synthesized by ring‐expansion of borole precursors with N3EMe3‐derived nitrenes. Desilylative hydrolysis of 1‐ and 2‐SiMe3 yielded the corresponding N‐protonated azaborinines, which were deprotonated with nBuLi or MN(SiMe3)2 (M=Na, K) to the corresponding group 1 salts, 1‐M and 2‐M. While the lithium salts crystallized as monomeric Lewis base adducts, the potassium salts formed coordination polymers or oligomers via intramolecular K⋅⋅⋅aryl π interactions. The reaction of 1‐M or 2‐M with CO2 yielded N‐carboxylate salts, which were derivatized by salt metathesis to methyl and silyl esters. Salt metathesis of 1‐M or 2‐M with methyl triflate, [Cp*BeCl] (Cp*=C5Me5), BBr2Ar (Ar=Ph, Mes, 2‐thienyl), ECl3 (E=B, Al, Ga) and PX3 (X=Cl, Br) afforded the respective group 2, 13 and 15 1,2‐azaborinin‐2‐yl complexes. Salt metathesis of 1‐K with BBr3 resulted not only in N‐borylation but also Ph‐Br exchange between the endocyclic and exocyclic boron atoms. Solution 11B NMR data suggest that the 1,2‐azaborinin‐2‐yl ligand is similarly electron‐withdrawing to a bromide. In the solid state the endocyclic bond length alternation and the twisting of the C4BN ring increase with the sterics of the substituents at the boron and nitrogen atoms, respectively. Regression analyses revealed that the downfield shift of the endocyclic 11B NMR resonances is linearly correlated to both the degree of twisting of the C4BN ring and the tilt angle of the N‐substituent. Calculations indicate that the 1,2‐azaborinin‐1‐yl ligand has no sizeable π‐donor ability and that the aromaticity of the ring can be subtly tuned by the electronics of the N‐substituent. [ABSTRACT FROM AUTHOR]

The reactions of carbodiimides with the iron arylborylene complex [Fe=BDur(CO)3(PMe3)] (Dur=2,3,5,6‐Me4C6H) and the iron bis(borylene) complex [Fe{=BDur}{=BN(SiMe3)2}(CO)3] yield a wide variety of temperature‐dependent products, including known FeBNC and novel FeBNB metallacycles, complexes of N‐heterocyclic boracarbene and spiro‐boracarbene ligands and a unique 1,3,2,4‐diazadiborolyl pianostool complex, characterized by NMR spectroscopy and X‐ray crystallography. The product distributions can be rationalized by considering sequences of cycloaddition, metathesis, insertion, and C−H activation pathways mainly governed by sterics. [ABSTRACT FROM AUTHOR]

A series of boranediyl-bridged diplatinum A-frame complexes, [Pt2X2(μ-BY)(μ-dmpm)2] (X = Cl, Br, I; Y = aryl, alkyl, amino, halo; dmpm = bis(dimethylphosphino)methane), were synthesised by the twofold oxidative addition of BX2Y to [Pt2(nbe)2(μ-dmpm)2] (nbe = norbornene) or to the paddlewheel complex [Pt2(μ-dmpm)3]. Similarly, the addition of B2X2(NMe2)2 (X = Cl, Br) to [Pt2(nbe)2(μ-dmpm)2] provided access to the diborane-1,2-diyl-bridged A-frame complexes [Pt2X2(μ-1,2-B2(NMe2)2)(μ-dmpm)2]. X-ray crystallographic studies of these (BY)n-bridged complexes show structural trends depending on the steric demands of Y and the nature of X. Analysis of higher-order 31P NMR satellites provided information on JP–Pt and JPt–Pt coupling constants, the latter correlating with the Pt⋯Pt distance. All (di)boranediyl complexes also proved unstable towards (successive) loss of the bridging "BY" unit(s), resulting in the formation of [Pt2X2(μ-dmpm)2]. [ABSTRACT FROM AUTHOR]

The concepts of aromaticity and antiaromaticity have a long history, and countless demonstrations of these phenomena have been made with molecules based on elements from the p, d, and f blocks of the periodic table. In contrast, the limited oxidation‐state flexibility of the s‐block metals has long stood in the way of their participation in sophisticated π‐bonding arrangements, and truly antiaromatic systems containing s‐block metals are altogether absent or remain poorly defined. Using spectroscopic, structural, and computational techniques, we present herein the synthesis and authentication of a heterocyclic compound containing the alkaline earth metal beryllium that exhibits significant antiaromaticity, and detail its chemical reduction and Lewis‐base‐coordination chemistry. [ABSTRACT FROM AUTHOR]

Das Konzept der Aromatizität und der Antiaromatizität ist seit langem bekannt, und zahlreiche Belege für dieses Phänomen wurden durch Moleküle, welche auf Elementen des p‐, d‐ und f‐Blocks des Periodensystems der Elemente (PSE) basieren, geliefert. Aufgrund der begrenzten Varianz des Oxidationszustandes von s‐Block‐Metallen konnten diese bisher nicht mit komplexen π‐Bindungssystemen interagieren. Daher gibt es keine bzw. nur schlecht beschriebene Beispiele für antiaromatische Systeme mit s‐Block‐Metallen. Durch die Verwendung von spektroskopischen, strukturanalytischen und quantenchemischen Methoden konnte eine heterocyclische Verbindung hergestellt und charakterisiert werden, welche das Erdalkalimetall Beryllium enthält und signifikante Antiaromatizität aufweist. Weiterhin beschreiben wir die Reaktivität gegenüber Lewis‐Basen und die chemische Reduktion dieser Verbindung. [ABSTRACT FROM AUTHOR]

Ein neuer Reaktionsweg für die Ringerweiterung von antiaromatischen Borolen mit organischen Aziden wird vorgestellt. Die gewöhnlich zu 1,2‐Azaborininen führende Reaktion eines Borols mit einem organischen Azid wurde durch die Veränderung der elektronischen Eigenschaften der Ausgangsverbindungen zur Bildung eines 1,2,3‐Diazaborinins umgeleitet. Das aus 1‐(2,3,4,5‐Tetraphenylborolyl)ferrocen mit 4‐Azido‐N,N‐dimethylanilin zunächst gebildete isolierbare Azo‐Azaborinin zersetzt sich thermisch zum 1,2,3‐Diazaborinin und Benzonitril. Die spektroskopischen Eigenschaften und die Reaktivität dieser heterocyclischen Verbindung zeigen Ähnlichkeiten zu Pyridinen, zu denen sie isoelektronisch ist. Dichtefunktionalrechnungen geben einen Einblick in den Mechanismus dieser ungewöhnlichen Umwandlung. Unerwartete Ringerweiterung: Ein neuer Reaktionsweg für die Ringerweiterung von Borolen mit organischen Aziden wurde gefunden, der statt eines 1,2‐Azaborinins ein 1,2,3‐Diazaborinin liefert. Während Dichtefunktionalrechnungen einen Einblick in den Mechanismus der BN2C3‐Ringbildung gewährten, offenbarten spektroskopische Studien sowie Untersuchungen zur Reaktivität Ähnlichkeiten des 1,2,3‐Diazaborinins mit Pyridin. [ABSTRACT FROM AUTHOR]

A new pathway for the ring expansion reaction of antiaromatic boroles with organic azides is reported. While the reaction usually leads to 1,2‐azaborinines, it was diverted to the formation of a 1,2,3‐diazaborinine by changing the electronic characteristics of the reagents. The isolable azo‐azaborinine intermediate initially formed from the reaction of 1‐(2,3,4,5‐tetraphenylborolyl)ferrocene with 4‐azido‐N,N‐dimethylaniline gradually decomposed to a 1,2,3‐diazaborinine and benzonitrile. Both the spectroscopic properties and the reactivity of the heteroaromatic compound show analogies to pyridine, to which it is isoelectronic. Density functional theory (DFT) calculations provided insight into the mechanism of this unusual transformation. Nitrile & error: A new pathway for the ring expansion reaction of boroles with organic azides is presented, leading to a 1,2,3‐diazaborinine instead of the expected 1,2‐azaborinine. Mechanistic DFT calculations provided insight into the mechanism of formation of the BN2C3 heterocycle, and spectroscopic and reactivity studies demonstrated the analogies of the 1,2,3‐diazaborinine to pyridine. [ABSTRACT FROM AUTHOR]

A carbene-stabilised neutral boryl radical and a boryl anion are isolated via selective one- and two-electron reduction of a diamidocarbene (DAC) adduct of dibromo(pentafluorophenyl)borane. Both the radical and the anion have been characterised by various spectroscopic techniques in solution, while the structures have been ascertained by single-crystal X-ray diffraction. In contrast, the reduction of the analogous cyclic (alkyl)(amino) carbene (CAAC) adduct yields a C–H activation product. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of a pentamethylcyclopentadienyl‐substituted dialane with a variety of Lewis bases results in unexpected disproportionation of the dialane into AlI and AlIII species. Use of a transition‐metal Lewis base allows for the formation of metal‐only Lewis pairs. Furthermore, the synthesis of a Lewis base bis‐adduct was successful with the Lewis base 4‐dimethylaminopyridine. [ABSTRACT FROM AUTHOR]

A series of NHC-supported 1,2-dithienyldiborenes was synthesized from the corresponding (dihalo)thienylborane NHC precursors. NMR and UV/Vis spectroscopic data, as well as X-ray crystallographic analyses, were used to assess the electronic and steric influences on the B=B double bond of various NHCs and electron-donating substituents on the thienyl ligands. Crystallographic data showed that the degree of coplanarity of the diborene core and thienyl groups is highly dependent on the sterics of the substituents. Furthermore, any increase in the electron-donating ability of the substituents resulted in the destabilization of the HOMO and greater instability of the resulting diborenes. [ABSTRACT FROM AUTHOR]

Boroles are important motifs within functional materials. With the aim to prepare a pinacolboryl-substituted derivative, the metallacycle transfer from corresponding zirconium and tin precursors has been explored. We show that the reaction of 1,1-dimethyl-2,3,4,5-tetrapinacolborylstannole with dichloro(phenyl)borane does not provide the desired borole, but instead a stannyl-substituted 1-chloroboracyclopent-3-ene. Spectroscopic and structural details of this highly functionalized boracycle indicate that intramolecular interactions between the tin and oxygen atoms of the boryl substituents may account for the unexpected outcome of the tin-boron exchange reaction. [ABSTRACT FROM AUTHOR]