TY - JOUR A1 - Muessig, Jonas H. A1 - Lisinetskaya, Polina A1 - Dewhurst, Rian D. A1 - Bertermann, Rüdiger A1 - Thaler, Melanie A1 - Mitric, Roland A1 - Braunschweig, Holger T1 - Tetraiododiborane(4) (B\(_2\)I\(_4\)) is a Polymer based on sp\(^3\) Boron in the Solid State JF - Angewandte Chemie International Edition N2 - Herein we present the first solid‐state structures of tetraiododiborane(4) (B\(_2\)I\(_4\)), which was long believed to exist in all phases as discrete molecules with planar, tricoordinate boron atoms, like the lighter tetrahalodiboranes(4) B\(_2\)F\(_4\), B\(_2\)Cl\(_4\), and B\(_2\)Br\(_4\). Single‐crystal X‐ray diffraction, solid‐state NMR, and IR measurements indicate that B\(_2\)I\(_4\) in fact exists as two different polymeric forms in the solid state, both of which feature boron atoms in tetrahedral environments. DFT calculations are used to simulate the IR spectra of the solution and solid‐state structures, and these are compared with the experimental spectra. KW - boron tetraiodide KW - boron KW - density functional theory KW - diborane KW - halides KW - solid-state sturcture Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-209428 VL - 59 ER - TY - JOUR A1 - Paprocki, Valerie A1 - Hrobárik, Peter A1 - Harriman, Katie L. M. A1 - Luff, Martin S. A1 - Kupfer, Thomas A1 - Kaupp, Martin A1 - Murugesu, Muralee A1 - Braunschweig, Holger T1 - Ein neutrales 1,4‐Diborabenzol als \(\pi\)‐Ligand in Actinoidkomplexen JF - Angewandte Chemie N2 - Die \(\pi\)-Koordination von Aren- und anionischen Heteroarenliganden ist ein allgegenwärtiges Strukturmotiv in der metallorganischen Chemie der d- und f-Block-Elemente. Im Gegensatz dazu sind vergleichbare \(\pi\)-Wechselwirkungen neutraler Heteroarene, darunter auch solche neutraler, aromatischer Borheterocyclen, für den f-Block weit weniger verbreitet, was z. T. mit einer geringeren Effektivität der Metall-zu-Ligand-Rückbindung in Zusammenhang gebracht werden kann. Für die Actinoide sind π-Komplexe mit neutralen Heteroarenliganden sogar gänzlich unbekannt. Durch Ausnutzung der außergewöhnlichen \(\pi\)-Donorstärke eines 1,4-Diborabenzols ist es uns nun gelungen, eine Reihe stabiler π-Halbsandwichkomplexe des Thoriums(IV) und des Urans(IV) über einen erstaunlich einfachen Zugang zu generieren: Umsetzung eines 1,4-Diborabenzols mit ThCl\(_{4}\)(dme)\(_{2}\) bzw. UCl\(_{4}\) in Gegenwart einer Lewis-Base. Hierdurch konnten die ersten Beispiele für Actinoidkomplexe mit einem neutralen Borheterocyclus als Sandwich-artigem Liganden erhalten werden. Laut experimentellen und theoretischen Studien ist die starke Actinoid-Heteroaren-Wechselwirkung in diesen Molekülen im Wesentlichen von elektrostatischer Natur. Der kovalente Hauptbeitrag wird hingegen von der Ligand-zu-Metall-\(\pi\)-Wechselwirkung geleistet, während \(\pi\)/δ-Rückbindungsanteile kaum eine Rolle spielen. KW - Actinoide KW - Bindungsverhältnisse KW - Bor KW - Heterocyclen KW - \(\pi\)-Komplexe Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218181 VL - 132 IS - 31 SP - 13209 EP - 13216 ER - TY - JOUR A1 - Saalfrank, Christian A1 - Fantuzzi, Felipe A1 - Kupfer, Thomas A1 - Ritschel, Benedikt A1 - Hammond, Kai A1 - Krummenacher, Ivo A1 - Bertermann, Rüdiger A1 - Wirthensohn, Raphael A1 - Finze, Maik A1 - Schmid, Paul A1 - Engel, Volker A1 - Engels, Bernd A1 - Braunschweig, Holger T1 - cAAC‐stabilisierte 9,10‐Diboraanthracene – offenschalige Singulettbiradikale JF - Angewandte Chemie N2 - Geringe HOMO-LUMO-Abstände und eine hohe Ladungsträgermobilität prädestinieren die höheren Acene für Anwendungen im Bereich der Organoelektronik. Die Leistungsfähigkeit derartiger Verbindungen steigt hierbei dramatisch mit der Anzahl anellierter Benzolringe. Größere Acenmengen sind synthetisch bisher jedoch nur für Acene bis Heptacen verlässlich zugänglich. Theoretischen Studien zufolge besitzen (Oligo)acene offenschalige Singulettbiradikal- und (Poly)acene polyradikalische Grundzustände. Eindeutige experimentelle Belege für diese Vorhersagen sind hingegen äußerst selten. Durch den Einbau von zwei Boratomen in das Anthracengrundgerüst konnten wir den HOMO-LUMO-Abstand von Acenen dramatisch verringern und zwar ohne die Notwendigkeit einer Ausweitung des konjugierten π-Systems. Stabilisierung der Borzentren durch cyclische (Alkyl)(amino)carbene lieferte hierbei neutrale 9,10-Diboraanthracene mit disjunkten, offenschaligen Singulettbiradikal-Grundzuständen. KW - Acene KW - Bindungsaktivierung KW - Biradikale KW - Bor KW - Heterocyclen Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218582 VL - 132 IS - 43 SP - 19502 EP - 19507 ER - TY - JOUR A1 - Goettel, James T. A1 - Gao, Haopeng A1 - Dotzauer, Simon A1 - Braunschweig, Holger T1 - \(^{Me}\)CAAC=N\(^{-}\): A Cyclic (Alkyl)(Amino)Carbene Imino Ligand JF - Chemistry – A European Journal N2 - A cyclic (alkyl)(amino)carbene (CAAC) has been shown to react with a covalent azide similar to the Staudinger reaction. The reaction of \(^{Me}\)CAAC with trimethylsilyl azide afforded the N‐silylated 2‐iminopyrrolidine (\(^{Me}\)CAAC=NSiMe\(_{3}\)), which was fully characterized. This compound undergoes hydrolysis to afford the 2‐iminopyrrolidine and trimethylsiloxane which co‐crystallize as a hydrogen‐bonded adduct. The N‐silylated 2‐iminopyrrolidine was used to transfer the novel pyrrolidine‐2‐iminato ligand onto both main‐group and transition‐metal centers. The reaction of the tetrabromodiborane bis(dimethyl sulfide) adduct with two equivalents of \(^{Me}\)CAAC=NSiMe\(_{3}\) afforded the disubstituted diborane. The reaction of \(^{Me}\)CAAC=NSiMe\(_{3}\) with TiCl\(_{4}\) and CpTiCl\(_{3}\) afforded \(^{Me}\)CAAC=NTiCl\(_{3}\) and \(^{Me}\)CAAC=NTiCl\(_{2}\)Cp, respectively. KW - boron KW - carbenes KW - imide ligands KW - nitrogen ligands KW - titanium Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-212662 VL - 26 IS - 5 ER - TY - JOUR A1 - Nees, Samuel A1 - Kupfer, Thomas A1 - Hofmann, Alexander A1 - Braunschweig, Holger T1 - Stabilisierung planarer Cyclopenten‐4‐yl‐Kationen durch Hyperkonjugation und π‐Delokalisierung JF - Angewandte Chemie N2 - Theoretischen Untersuchungen zufolge stellt das planare Cyclopenten-4-yl-Kation das energetisch ungünstigste C\(_{5}\)H\(_{7}\)\(^{+}\)-Isomer dar und ist am ehesten als klassisches Carbokation zu beschreiben, wobei dessen Existenz experimentell bislang noch nicht nachgewiesen werden konnte. Durch Umsetzung sterisch überfrachteter Alane vom Typ Cp\(^{R}\)AlBr\(_{2}\) mit AlBr3 ist uns nun die Isolierung zweier stabiler Derivate des Cyclopenten-4-yl-Kations gelungen. Untersuchungen zu deren (elektronischer) Struktur (XRD, QM) offenbarten planare Geometrien und starke Hyperkonjugationswechselwirkungen zwischen den C-Al-σ-Bindungen und dem unbesetzten p-Orbital der kationischen sp\(^{2}\)-Kohlenstoffzentren. Die Analyse der Molekülorbitale (MOs), der Anisotropie der induzierten Stromdichte (ACID) sowie verschiedener Aromatizitätsdeskriptoren deuten hierbei auf ein hohes Maß an Delokalisierung und π-Aromatizität in diesen Systemen hin, was einer klassischen Beschreibung grundlegend widerspricht. Unsere Cyclopenten-4-yl-Kationen gehören somit zu den wenigen Beispielen aromatischer Carbocyclen, in denen eine Delokalisierung der π-Elektronen über gesättigte sp\(^{3}\)-Kohlenstoffatome hinweg beobachtet wird. KW - ACID KW - Carbokationen KW - Cyclopenten-4-yl-Kation KW - Hyperkonjugation KW - π-Aromatizität Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218456 VL - 132 IS - 42 SP - 18971 EP - 18978 ER - TY - JOUR A1 - Schmidt, Uwe A1 - Werner, Luis A1 - Arrowsmith, Merle A1 - Deissenberger, Andrea A1 - Hermann, Alexander A1 - Hofmann, Alexander A1 - Ullrich, Stefan A1 - Mattock, James D. A1 - Vargas, Alfredo A1 - Braunschweig, Holger T1 - Trans‐selektive Dihydroborierung eines cis‐Diborens durch Insertion: Synthese eines linearen sp\(^3\)‐sp\(^2\)‐sp\(^3\)‐Triborans und anschließende Kationisierung JF - Angewandte Chemie N2 - Die Reaktion zwischen Aryl‐ und Amino(dihydro)boranen und Dibora[2]ferrocenophan 1 führt zur Bildung von 1,3‐trans‐Dihydrotriboranen durch formale Hydrierung und Insertion eines Borylens in die B=B Doppelbindung. Die Aryltriboran‐Derivate unterliegen einer reversiblen Photoisomerisierung zugunsten eines cis‐1,2‐μ‐H‐3‐Hydrotriborans, während eine Hydridabstraktion zu kationischen Triboranen führt, welche die ersten doppelt basenstabilisierten B\(_3\)H\(_4\)\(^+\)‐Analoga darstellen. KW - Diboren KW - Hydroborierung KW - Kation KW - Photoisomerisierung KW - Triboran Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-219713 VL - 132 IS - 1 ER - TY - JOUR A1 - Schmidt, Uwe A1 - Werner, Luis A1 - Arrowsmith, Merle A1 - Deissenberger, Andrea A1 - Hermann, Alexander A1 - Hofmann, Alexander A1 - Ullrich, Stefan A1 - Mattock, James D. A1 - Vargas, Alfredo A1 - Braunschweig, Holger T1 - trans-Selective Insertional Dihydroboration of a cis-Diborene: Synthesis of Linear sp\(^3\)-sp\(^2\)-sp\(^3\)-Triboranes and Subsequent Cationization JF - Angewandte Chemie International Edition N2 - The reaction of aryl‐ and amino(dihydro)boranes with dibora[2]ferrocenophane 1 leads to the formation 1,3‐trans ‐dihydrotriboranes by formal hydrogenation and insertion of a borylene unit into the B=B bond. The aryltriborane derivatives undergo reversible photoisomerization to the cis ‐1,2‐μ‐H‐3‐hydrotriboranes, while hydride abstraction affords cationic triboranes, which represent the first doubly base‐stabilized B3H4\(^+\) analogues. KW - cations KW - hydroboration KW - photoisomerization KW - triboranes KW - diborenes Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-208090 VL - 59 IS - 1 ER - TY - JOUR A1 - Hermann, Alexander A1 - Fantuzzi, Felipe A1 - Arrowsmith, Merle A1 - Zorn, Theresa A1 - Krummenacher, Ivo A1 - Ritschel, Benedikt A1 - Radacki, Krzysztof A1 - Engels, Bernd A1 - Braunschweig, Holger T1 - Oxidation, Coordination, and Nickel-Mediated Deconstruction of a Highly Electron-Rich Diboron Analogue of 1,3,5-Hexatriene JF - Angewandte Chemie, International Edition N2 - The reductive coupling of an N-heterocyclic carbene (NHC) stabilized (dibromo)vinylborane yields a 1,2-divinyl- diborene, which, although isoelectronic to a 1,3,5-triene, displays no extended p conjugation because of twisting of the C\(_2\)B\(_2\)C\(_2\) chain. While this divinyldiborene coordinates to copper(I) and platinum(0) in an η\(^2\)-B\(_2\) and η\(^4\)-C\(_2\)B\(_2\) fashion, respectively, it undergoes a complex rearrangement to an η\(^4\)-1,3-diborete upon complexation with nickel(0). KW - boron KW - diborenes KW - carbenes KW - conjugation KW - density-functional calculations KW - rearrangements KW - structure elucidation Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-240652 VL - 59 IS - 36 ER - TY - JOUR A1 - Rauch, Florian A1 - Endres, Peter A1 - Friedrich, Alexandra A1 - Sieh, Daniel A1 - Hähnel, Martin A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Finze, Maik A1 - Ji, Lei A1 - Marder, Todd B. T1 - An Iterative Divergent Approach to Conjugated Starburst Borane Dendrimers JF - Chemistry – A European Journal N2 - Using a new divergent approach, conjugated triarylborane dendrimers were synthesized up to the 2nd generation. The synthetic strategy consists of three steps: 1) functionalization, via iridium catalyzed C−H borylation; 2) activation, via fluorination of the generated boronate ester with K[HF\(_{2}\)] or [N(nBu\(_{4}\))][HF\(_{2}\)]; and 3) expansion, via reaction of the trifluoroborate salts with aryl Grignard reagents. The concept was also shown to be viable for a convergent approach. All but one of the conjugated borane dendrimers exhibit multiple, distinct and reversible reduction potentials, making them potentially interesting materials for applications in molecular accumulators. Based on their photophysical properties, the 1st generation dendrimers exhibit good conjugation over the whole system. However, the conjugation does not increase further upon expansion to the 2nd generation, but the molar extinction coefficients increase linearly with the number of triarylborane subunits, suggesting a potential application as photonic antennas. KW - density functional calculations KW - electron storage KW - luminescence KW - redox KW - triarylborane Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218345 VL - 26 IS - 57 SP - 12951 EP - 12963 ER - TY - JOUR A1 - Nees, Samuel A1 - Kupfer, Thomas A1 - Hofmann, Alexander A1 - Braunschweig, Holger T1 - Planar Cyclopenten‐4‐yl Cations: Highly Delocalized π Aromatics Stabilized by Hyperconjugation JF - Angewandte Chemie International Edition N2 - Theoretical studies predicted the planar cyclopenten‐4‐yl cation to be a classical carbocation, and the highest‐energy isomer of C\(_{5}\)H\(_{7}\)\(^{+}\). Hence, its existence has not been verified experimentally so far. We were now able to isolate two stable derivatives of the cyclopenten‐4‐yl cation by reaction of bulky alanes Cp\(^{R}\)AlBr\(_{2}\) with AlBr3. Elucidation of their (electronic) structures by X‐ray diffraction and quantum chemistry studies revealed planar geometries and strong hyperconjugation interactions primarily from the C−Al σ bonds to the empty p orbital of the cationic sp\(^{2}\) carbon center. A close inspection of the molecular orbitals (MOs) and of the anisotropy of current (induced) density (ACID), as well as the evaluation of various aromaticity descriptors indicated distinct aromaticity for these cyclopenten‐4‐yl derivatives, which strongly contrasts the classical description of this system. Here, strong delocalization of π electrons spanning the whole carbocycle has been verified, thus providing rare examples of π aromaticity involving saturated sp\(^{3}\) carbon atoms. KW - ACID KW - carbocations KW - cyclopenten-4-yl cation KW - hyperconjugation KW - π aromaticity Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218358 VL - 59 IS - 42 SP - 18809 EP - 18815 ER - TY - JOUR A1 - Rauch, Florian A1 - Fuchs, Sonja A1 - Friedrich, Alexandra A1 - Sieh, Daniel A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Finze, Maik A1 - Marder, Todd B. T1 - Highly Stable, Readily Reducible, Fluorescent, Trifluoromethylated 9‐Borafluorenes JF - Chemistry – A European Journal N2 - Three different perfluoroalkylated borafluorenes (\(^{F}\)Bf) were prepared and their electronic and photophysical properties were investigated. The systems have four trifluoromethyl moieties on the borafluorene moiety as well as two trifluoromethyl groups at the ortho positions of their exo‐aryl moieties. They differ with regard to the para substituents on their exo‐aryl moieties, being a proton \(^{F}\)Xyl\(^{F}\)Bf, \(^{F}\)Xyl: 2,6‐bis(trifluoromethyl)phenyl), a trifluoromethyl group (\(^{F}\)Mes\(^{F}\)Bf, \(^{F}\)Mes: 2,4,6‐tris(trifluoromethyl)phenyl) or a dimethylamino group (p‐NMe\(_{2}\)‐\(^{F}\)Xyl\(^{F}\)Bf, p‐NMe\(_{2}\)‐\(^{F}\)Xyl: 4‐(dimethylamino)‐2,6‐bis(trifluoromethyl)phenyl), respectively. All derivatives exhibit extraordinarily low reduction potentials, comparable to those of perylenediimides. The most electron‐deficient derivative \(^{F}\)Mes\(^{F}\)Bf was also chemically reduced and its radical anion isolated and characterized. Furthermore, all compounds exhibit very long fluorescent lifetimes of about 250 ns up to 1.6 μs; however, the underlying mechanisms responsible for this differ. The donor‐substituted derivative p‐NMe\(_{2}\)‐\(^{F}\)Xyl\(^{F}\)Bf exhibits thermally activated delayed fluorescence (TADF) from a charge‐transfer (CT) state, whereas the \(^{F}\)Mes\(^{F}\)Bf and FXylFBf borafluorenes exhibit only weakly allowed locally excited (LE) transitions due to their symmetry and low transition‐dipole moments. KW - borafluorenes KW - boron KW - EPR spectroscopy KW - fluorescence KW - heterocycles Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218390 VL - 26 IS - 56 SP - 12794 EP - 12808 ER - TY - JOUR A1 - Huang, Zhenguo A1 - Wang, Suning A1 - Dewhurst, Rian D. A1 - Ignat'ev, Nikolai V. A1 - Finze, Maik A1 - Braunschweig, Holger T1 - Boron: Its Role in Energy‐Related Processes and Applications JF - Angewandte Chemie International Edition N2 - Boron's unique position in the Periodic Table, that is, at the apex of the line separating metals and nonmetals, makes it highly versatile in chemical reactions and applications. Contemporary demand for renewable and clean energy as well as energy‐efficient products has seen boron playing key roles in energy‐related research, such as 1) activating and synthesizing energy‐rich small molecules, 2) storing chemical and electrical energy, and 3) converting electrical energy into light. These applications are fundamentally associated with boron's unique characteristics, such as its electron‐deficiency and the availability of an unoccupied p orbital, which allow the formation of a myriad of compounds with a wide range of chemical and physical properties. For example, boron's ability to achieve a full octet of electrons with four covalent bonds and a negative charge has led to the synthesis of a wide variety of borate anions of high chemical and electrochemical stability—in particular, weakly coordinating anions. This Review summarizes recent advances in the study of boron compounds for energy‐related processes and applications. KW - boron KW - electrolytes KW - hydrogen KW - OLEDs KW - small-molecule activation Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218514 VL - 59 IS - 23 SP - 8800 EP - 8816 ER - TY - JOUR A1 - Brückner, Tobias A1 - Dewhurst, Rian D. A1 - Dellermann, Theresa A1 - Müller, Marcel A1 - Braunschweig, Holger T1 - Mild synthesis of diboryldiborenes by diboration of B–B triple bonds JF - Chemical Science N2 - A set of diboryldiborenes are prepared by the mild, catalyst-free, room-temperature diboration of the B–B triple bonds of doubly base-stabilized diborynes. Two of the product diboryldiborenes are found to be air- and water-stable in the solid state, an effect that is attributed to their high crystallinity and extreme insolubility in a wide range of solvents. KW - boron KW - diborenes KW - diboration KW - triple bonds KW - diborynes Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-186306 VL - 10 ER - TY - INPR A1 - Légaré, Marc-André A1 - Pranckevicius, Conor A1 - Braunschweig, Holger T1 - Metallomimetic Chemistry of Boron T2 - Chemical Reviews N2 - The study of main-group molecules that behave and react similarly to transition-metal (TM) complexes has attracted significant interest in recent decades. Most notably, the attractive idea of replacing the all-too-often rare and costly metals from catalysis has motivated efforts to develop main-group-element-mediated reactions. Main-group elements, however, lack the electronic flexibility of TM complexes that arises from combinations of empty and filled d orbitals and that seem ideally suited to bind and activate many substrates. In this review, we look at boron, an element that despite its nonmetal nature, low atomic weight, and relative redox staticity has achieved great milestones in terms of TM-like reactivity. We show how in interelement cooperative systems, diboron molecules, and hypovalent complexes the fifth element can acquire a truly metallomimetic character. As we discuss, this character is powerfully demonstrated by the reactivity of boron-based molecules with H2, CO, alkynes, alkenes and even with N2. KW - boron KW - small-molecule activation KW - catalysis KW - low-valent main group chemistry Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-186317 N1 - This document is the unedited Author’sv ersion of a Submitted Work that was subsequently accepted for publication in Chemical Reviews,copyright ©American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/acs.chemrev.8b00561. ER - TY - INPR A1 - Brückner, Tobias A1 - Stennett, Tom E. A1 - Heß, Merlin A1 - Braunschweig, Holger T1 - Single and Double Hydroboration of B-B Triple Bonds and Conver- gent Routes to a Cationic Tetraborane T2 - Journal of the American Chemical Society N2 - A compound with a boron-boron triple bond is shown to undergo stepwise hydroboration reactions with catecholborane to yield an unsymmetrical hydro(boryl)diborene and a 2,3-dihydrotetraborane. Abstraction of H– from the latter compound produces an unusual cationic, planar tetraborane with a hydrogen atom bridging the central B2 moiety. Spectroscopic and crystallographic data and DFT calculations support a ‘protonated diborene’ structure for this compound, which can also be accessed via direct protonation of the corresponding diborene. KW - boron KW - multiple bonding KW - hydroboration Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-188632 N1 - This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Journal of the American Chemical Society, copyright © American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/jacs.9b07991. ER - TY - INPR A1 - Muessig, Jonas H. A1 - Thaler, Melanie A1 - Dewhurst, Rian D. A1 - Paprocki, Valerie A1 - Seufert, Jens A1 - Mattock, James D. A1 - Vargas, Alfredo A1 - Braunschweig, Holger T1 - Phosphine-Stabilized Diiododiborenes: Isolable Diborenes with Six Labile Bonds T2 - Angewandte Chemie, International Edition N2 - The lability of B=B, B-P and B-halide bonds is combined in the syntheses of the first diiododiborenes. In a series of reactivity tests, these diiododiborenes demonstrate cleavage of all six of their central bonds in different ways, leading to products of B=B hydrogenation and dihalogenation as well as halide exchange. KW - boron KW - low-valent main-group species KW - iodine KW - multiple bonding KW - 1,2-additions Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-178608 N1 - This is the pre-peer reviewed version of the following article: J. H. Muessig, M. Thaler, R. D. Dewhurst, V. Paprocki, J. Seufert, J. D. Mattock, A. Vargas, H. Braunschweig, Angew. Chem. Int. Ed. 2019, 58, 4405, which has been published in final form at https://doi.org/10.1002/anie.201814230. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. ER - TY - INPR A1 - Brückner, Tobias A1 - Arrowsmith, Merle A1 - Heß, Merlin A1 - Hammond, Kai A1 - Müller, Marcel A1 - Braunschweig, Holger T1 - Synthesis of fused B,N-heterocycles by alkyne cleavage, NHC ring-expansion and C-H activation at a diboryne T2 - Chemical Communications N2 - The addition of alkynes to a staturated N-heterocyclic carbene (NHC)-supported diboryne results in spontaneous cycloaddition, with complete B≡B and C≡C triple bond cleavage, NHC ring- expansion and activation of a variety of C-H bonds, leading to the formation of complex mixtures of fused B,N-heterocycles. KW - heterocycles KW - alkynes KW - boron KW - carbenes Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-184899 N1 - This is the pre-peer reviewed version of the following article: Chem. Commun., 2019,55, 6700-6703, which has been published in final form at doi:10.1039/C9CC02657F ER - TY - INPR A1 - Stennett, Tom E. A1 - Bissinger, Philipp A1 - Griesbeck, Stefanie A1 - Ullrich, Stefan A1 - Krummenacher, Ivo A1 - Auth, Michael A1 - Sperlich, Andreas A1 - Stolte, Matthias A1 - Radacki, Krzysztof A1 - Yao, Chang-Jiang A1 - Würthner, Frank A1 - Steffen, Andreas A1 - Marder, Todd B. A1 - Braunschweig, Holger T1 - Near-Infrared Quadrupolar Chromophores Combining Three-Coordinate Boron-Based Superdonor and Superacceptor Units T2 - Angewandte Chemie, International Edition N2 - In this work, two new quadrupolar A-π-D-π-A chromophores have been prepared featuring a strongly electron- donating diborene core and strongly electron-accepting dimesitylboryl F(BMes2) and bis(2,4,6-tris(trifluoromethyl)phenyl)boryl (BMes2) end groups. Analysis of the compounds by NMR spectroscopy, X-ray crystallography, cyclic voltammetry and UV-vis-NIR absorption and emission spectroscopy indicated that the compounds possess extended conjugated π-systems spanning their B4C8 cores. The combination of exceptionally potent π-donor (diborene) and π- acceptor (diarylboryl) groups, both based on trigonal boron, leads to very small HOMO-LUMO gaps, resulting in strong absorption in the near-IR region with maxima in THF at 840 and 1092 nm, respectively, and very high extinction coefficients of ca. 120,000 M-1cm-1. Both molecules also display weak near-IR fluorescence with small Stokes shifts. KW - boron KW - near-IR chromophores KW - conjugation KW - low-valent compounds KW - synthesis Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-180391 N1 - This is the pre-peer reviewed version of the following article: T. E. Stennett, P. Bissinger, S. Griesbeck, S. Ullrich, I. Krummenacher, M. Auth, A. Sperlich, M. Stolte, K. Radacki, C.-J. Yao, F. Wuerthner, A. Steffen, T. B. Marder, H. Braunschweig, Angew. Chem. Int. Ed. 2019, 58, 6449. , which has been published in final form at https://doi.org/10.1002/anie.201900889. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. ER - TY - INPR A1 - Arrowsmith, Merle A1 - Dömling, Michael A1 - Schmidt, Uwe A1 - Werner, Luis A1 - Castro, Abril C. A1 - Jiménez-Halla, J. Oscar C. A1 - Müssig, Jonas A1 - Prieschl, Dominic A1 - Braunschweig, Holger T1 - Spontaneous trans‐Selective Transfer Hydrogenation of Apolar B=B Double Bonds T2 - Angewandte Chemie, International Edition N2 - The transfer hydrogenation of NHC-supported diborenes with dimethylamine borane proceeds with high selectivity for the trans-1,2-dihydrodiboranes(6). DFT calculations suggest a stepwise proton-first-hydride-second reaction mechanism via an intermediate μ-hydrodiboronium dimethylaminoborate ion pair. KW - transfer hydrogenation KW - diborene KW - amine borane dehydrocoupling KW - diboranes KW - DFT mechanism Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-184874 N1 - This is the pre-peer reviewed version of the following article: M. Dömling, M. Arrowsmith, U. Schmidt, L. Werner, A. C. Castro, J. O. C. Jiménez-Halla, R. Bertermann, J. Müssig, D. Prieschl, H. Braunschweig, Angew. Chem. Int. Ed. 2019, 58, 9782. doi:10.1002/anie.201902656, which has been published in final form at https://doi.org/10.1002/anie.201902656. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. ER - TY - INPR A1 - Englert, Lukas A1 - Stoy, Andreas A1 - Arrowsmith, Merle A1 - Müssig, Jonas H. A1 - Thaler, Melanie A1 - Deißenberger, Andrea A1 - Häfner, Alena A1 - Böhnke, Julian A1 - Hupp, Florian A1 - Seufert, Jens A1 - Mies, Jan A1 - Damme, Alexander A1 - Dellermann, Theresa A1 - Hammond, Kai A1 - Kupfer, Thomas A1 - Radacki, Krzysztof A1 - Thiess, Torsten A1 - Braunschweig, Holger T1 - Stable Lewis Base Adducts of Tetrahalodiboranes: Synthetic Methods and Structural Diversity T2 - Chemistry - A European Journal N2 - A series of 22 new bis(phosphine), bis(carbene) and bis(isonitrile) tetrahalodiborane adducts has been synthesized, either by direct adduct formation with highly sensitive B2X4 precursors (X = Cl, Br, I) or by ligand exchange at stable B2X4(SMe2)2 precursors (X = Cl, Br) with labile dimethylsulfide ligands. The isolated compounds have been fully characterized using NMR spectroscopic, (C,H,N)- elemental and, for 20 of these compounds, X-ray crystallographic analysis, revealing an unexpected variation in the bonding motifs. Besides the classical B2X4L2 diborane(6) adducts, some of the more sterically demanding carbene ligands induce a halide displacement leading to the first halide-bridged monocationic diboron species, [B2X3L2]A (A = BCl4, Br, I). Furthermore, low-temperature 1:1 reactions of B2Cl4 with sterically demanding N-heterocyclic carbenes led to the formation of kinetically unstable mono-adducts, one of which was structurally characterized. A comparison of the NMR and structural data of new and literature-known bis-adducts shows several trends pertaining to the nature of the halides and the stereoelectronic properties of the Lewis bases employed. KW - diborane(6) KW - Lewis-base adducts KW - ligand exchange KW - crystallography KW - NMR spectroscopy Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-184888 N1 - This is the pre-peer reviewed version of the following article: L. Englert, A. Stoy, M. Arrowsmith, J. H. Muessig, M. Thaler, A. Deißenberger, A. Häfner, J. Böhnke, F. Hupp, J. Seufert, J. Mies, A. Damme, T. Dellermann, K. Hammond, T. Kupfer, K. Radacki, T. Thiess, H. Braunschweig, Chem. Eur. J. 2019, 25, 8612. https://doi.org/10.1002/chem.201901437, which has been published in final form at https://doi.org/10.1002/chem.201901437. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. ER - TY - JOUR A1 - He, Jiang A1 - Rauch, Florian A1 - Friedrich, Alexandra A1 - Sieh, Daniel A1 - Ribbeck, Tatjana A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Finze, Maik A1 - Marder, Todd B. T1 - N-Heterocyclic Olefins as Electron Donors in Combination with Triarylborane Acceptors: Synthesis, Optical and Electronic Properties of D-π-A Compounds JF - Chemistry - A European Journal N2 - N‐heterocyclic olefins (NHOs), relatives of N‐heterocyclic carbenes (NHCs), exhibit high nucleophilicity and soft Lewis basic character. To investigate their π‐electron donating ability, NHOs were attached to triarylborane π‐acceptors (A) giving donor (D)–π–A compounds 1–3. In addition, an enamine π‐donor analogue (4) was synthesized for comparison. UV–visible absorption studies show a larger red shift for the NHO‐containing boranes than for the enamine analogue, a relative of cyclic (alkyl)(amino) carbenes (CAACs). Solvent‐dependent emission studies indicate that 1–4 have moderate intramolecular charge‐transfer (ICT) behavior. Electrochemical investigations reveal that the NHO‐containing boranes have extremely low reversible oxidation potentials (e.g., for 3, \(E^{ox}_{1/2}\) =−0.40 V vs. ferrocene/ferrocenium, Fc/Fc\(^+\), in THF). Time‐dependent (TD) DFT calculations show that the HOMOs of 1–3 are much more destabilized than that of the enamine‐containing 4, which confirms the stronger donating ability of NHOs. KW - donor-acceptor systems KW - electrochemistry KW - photophysical prosperties KW - N-heterocyclic olefins KW - triarylboranes Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-204690 VL - 25 ER - TY - JOUR A1 - Thiess, Torsten A1 - Mellerup, Soren K. A1 - Braunschweig, Holger T1 - B–B Cleavage and Ring-Expansion of a 1,4,2,3-Diazadiborinine with N-Heterocyclic Carbenes JF - Chemistry - A European Journal N2 - A 1,4,2,3‐diazadiborinine derivative was found to form Lewis adducts with strong two‐electron donors such as N‐heterocyclic and cyclic (alkyl)(amino)carbenes. Depending on the donor, some of these Lewis pairs are thermally unstable, converting to sole B,N‐embedded products upon gentle heating. The products of these reactions, which have been fully characterized by NMR spectroscopy, elemental analysis, and single‐crystal X‐ray diffraction, were identified as B,N‐heterocycles with fused 1,5,2,4‐diazadiborepine and 1,4,2‐diazaborinine rings. Computational modelling of the reaction mechanism provides insight into the formation of these unique structures, suggesting that a series of B−H, C−N, and B−B bond activation steps are responsible for these “intercalation” reactions between the 1,4,2,3‐diazadiborinine and NHCs. KW - B,N-heterocylcles KW - B-B bond activation KW - diazadiborinines KW - NHCs KW - ring-expansion reactions Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-206173 VL - 25 IS - 59 ER - TY - JOUR A1 - Hattori, Yohei A1 - Michail, Evripidis A1 - Schmiedel, Alexander A1 - Moos, Michael A1 - Holzapfel, Marco A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Müller, Ulrich A1 - Pflaum, Jens A1 - Lambert, Christoph T1 - Luminescent Mono-, Di-, and Tri-radicals: Bridging Polychlorinated Triarylmethyl Radicals by Triarylamines and Triarylboranes JF - Chemistry - A European Journal N2 - Up to three polychlorinated pyridyldiphenylmethyl radicals bridged by a triphenylamine carrying electron withdrawing (CN), neutral (Me), or donating (OMe) groups were synthesized and analogous radicals bridged by tris(2,6‐dimethylphenyl)borane were prepared for comparison. All compounds were as stable as common closed‐shell organic compounds and showed significant fluorescence upon excitation. Electronic, magnetic, absorption, and emission properties were examined in detail, and experimental results were interpreted using DFT calculations. Oxidation potentials, absorption and emission energies could be tuned depending on the electron density of the bridges. The triphenylamine bridges mediated intramolecular weak antiferromagnetic interactions between the radical spins, and the energy difference between the high spin and low spin states was determined by temperature dependent ESR spectroscopy and DFT calculations. The fluorescent properties of all radicals were examined in detail and revealed no difference for high and low spin states which facilitates application of these dyes in two‐photon absorption spectroscopy and OLED devices. KW - density functional calculations KW - fluorescence KW - NIR OLED KW - radical KW - two-photon absorption Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-208162 VL - 25 IS - 68 ER - TY - JOUR A1 - Bélanger-Chabot, Guillaume A1 - Braunschweig, Holger T1 - Hexahalogendiborat‐Dianionen: Eine neue Klasse binärer Borhalogenide JF - Angewandte Chemie N2 - Die elektronenpräzisen binären Borsubhalogenide [B\(_2\)X\(_6\)]\(^{2−}\) (X=F, Br, I) wurden synthetisiert und strukturell im Festkörper untersucht. Zudem konnte die vermutete Existenz von [B\(_2\)Cl\(_6\)]\(^{2−}\) mittels Röntgendiffraktometrie nachgewiesen werden. Diese Dianionen sind isoelektronisch zu den Hexahalogeniden des Ethans und können als Homologe des Tetrahalogenborat‐Anions BX\(_4\)\(^−\) betrachtet werden. Darüber hinaus gehören sie zu den seltenen Beispielen von elektronenpräzisen binären Borverbindungen (B\(_2\)X\(_4\), BX\(_3\), [BX\(_4\)]\(^−\)). KW - Binäre Verbindungen KW - Bor KW - Elektronenpräzise Diborate KW - Halogene Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-212605 VL - 131 IS - 40 ER - TY - JOUR A1 - Lenczyk, Carsten A1 - Roy, Dipak Kumar A1 - Oberdorf, Kai A1 - Nitsch, Jörn A1 - Dewhurst, Rian D. A1 - Radacki, Krzysztof A1 - Halet, Jean-François A1 - Marder, Todd B. A1 - Bickelhaupt, Matthias A1 - Braunschweig, Holger T1 - Toward Transition‐Metal‐Templated Construction of Arylated B\(_{4}\) Chains by Dihydroborane Dehydrocoupling JF - Chemistry - A European Journal N2 - The reactivity of a diruthenium tetrahydride complex towards three selected dihydroboranes was investigated. The use of [DurBH\(_{2}\)] (Dur=2,3,5,6‐Me\(_{4}\)C\(_{6}\)H) and [(Me\(_{3}\)Si)\(_{2}\)NBH\(_{2}\)] led to the formation of bridging borylene complexes of the form [(Cp\(^{*}\)RuH)\(_{2}\)BR] (Cp\(^{*}\)=C\(_{5}\)Me\(_{5}\); 1 a: R=Dur; 1 b: R=N(SiMe\(_{3}\))\(_{2}\)) through oxidative addition of the B−H bonds with concomitant hydrogen liberation. Employing the more electron‐deficient dihydroborane [3,5‐(CF\(_{3}\))\(_{2}\)‐C\(_{6}\)H\(_{3}\)BH\(_{2}\)] led to the formation of an anionic complex bearing a tetraarylated chain of four boron atoms, namely Li(THF)\(_{4}\)[(Cp\(^{*}\)Ru)\(_{2}\)B\(_{4}\)H\(_{5}\)(3,5‐(CF\(_{3}\))\(_{2}\)C\(_{6}\)H\(_{3}\))\(_{4}\)] (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)B\(_{4}\)H\(_{9}\)] (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 B\(_{4}\) chain better resembles a network of three B−B σ bonds, the central bond being significantly weaker than the other two. KW - transition metal KW - B−H activation KW - boron KW - dehydrocoupling KW - ruthenium Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-214324 VL - 25 IS - 72 ER - TY - JOUR A1 - Lenczyk, Carsten A1 - Roy, Dipak Kumar A1 - Nitsch, Jörn A1 - Radacki, Krzysztof A1 - Rauch, Florian A1 - Dewhurst, Rian D. A1 - Bickelhaupt, F. Matthias A1 - Marder, Todd B. A1 - Braunschweig, Holger T1 - Steric Effects Dictate the Formation of Terminal Arylborylene Complexes of Ruthenium from Dihydroboranes JF - Chemistry - A European Journal N2 - The steric and electronic properties of aryl substituents in monoaryl borohydrides (Li[ArBH\(_3\)]) and dihydroboranes were systematically varied and their reactions with [Ru(PCy\(_3\))\(_2\)HCl(H\(_2\))] (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. KW - Arylborylene Complexes KW - Ruthenium KW - Dihydroboranes KW - boranes KW - borohydrides KW - borylenes KW - steric effects KW - sigma boranes Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-219537 SN - 1521-3765 VL - 25 IS - 59 ER - TY - JOUR A1 - Bélanger‐Chabot, Guillaume A1 - Braunschweig, Holger T1 - Hexahalodiborate Dianions: A New Family of Binary Boron Halides JF - Angewandte Chemie International Edition N2 - The electron‐precise binary boron subhalide species [B\(_2\)X\(_6\)]\(^{2−}\) X=F, Br, I) were synthesized and their structures confirmed by X‐ray crystallography. The existence of the previously claimed [B\(_2\)Cl\(_6\)]\(^{2−}\), 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 (BX\(_4\)\(^−\)), and are rare examples of molecular electron‐precise binary boron species beyond B\(_2\)X\(_4\), BX\(_3\), and [BX\(_4\)]\(^−\). KW - binary species KW - boron KW - electron-precise diborates KW - halogens Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-219688 VL - 58 IS - 40 ER - TY - INPR A1 - Auerhammer, Dominic A1 - Arrowsmith, Merle A1 - Böhnke, Julian A1 - Braunschweig, Holger A1 - Dewhurst, Rian D. A1 - Kupfer, Thomas T1 - Brothers from Another Mother: a Borylene and its Dimer are Non-Interconvertible but Connected through Reactivity T2 - Chemical Science N2 - The self-stabilizing, tetrameric cyanoborylene [(cAAC)B(CN)]4 (I, cAAC = 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) and its diborene relative, [(cAAC)(CN)B=B(CN)(cAAC)] (II), both react with disulfides and diselenides to yield the corresponding cAAC-supported cyanoboron bis(chalcogenides). Furthermore, reactions of I or II with elemental sulfur and selenium in various stoichiometries provided access to a variety of cAAC- stabilized cyanoboron-chalcogen heterocycles, including a unique dithiaborirane, a diboraselenirane, 1,3-dichalcogena-2,4-diboretanes, 1,3,4-trichalcogena- 2,5-diborolanes and a rare six-membered 1,2,4,5-tetrathia-3,6-diborinane. Stepwise addition reactions and solution stability studies provided insights into the mechanism of these reactions and the subtle differences in reactivity observed between I and II. KW - borylenes KW - diborenes KW - boron KW - carbenes KW - chalcogens Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-157125 ER - TY - INPR A1 - Böhnke, Julian A1 - Braunschweig, Holger A1 - Jiménez-Halla, Oscar A1 - Krummenacher, Ivo A1 - Stennett, Tom E. T1 - Half-Sandwich Complexes of an Extremely Electron-Donating, Re-dox-Active η\(^6\)-Diborabenzene Ligand T2 - Journal of the American Chemical Society N2 - The heteroarene 1,4-bis(CAAC)-1,4-diborabenzene (1; CAAC = cyclic (alkyl)(amino)carbene) reacts with [(MeCN)\(_3\)M(CO)\(_3\)] (M = Cr, Mo, W) to yield half-sandwich complexes of the form [(η\(^6\)-diborabenzene)M(CO)\(_3\)] (M = Cr (2), Mo (3), W (4)). Investigation of the new complexes with a combination of X-ray diffraction, spectroscopic methods and DFT calculations shows that ligand 1 is a remarkably strong electron donor. In particular, [(η\(^6\)-arene)M(CO)\(_3\)] complexes of this ligand display the lowest CO stretching frequencies yet observed for this class of complex. Cyclic voltammetry on complexes 2-4 revealed one reversi- ble oxidation and two reversible reduction events in each case, with no evidence of ring-slippage of the arene to the η\(^4\) binding mode. Treatment of 4 with lithium metal in THF led to identification of the paramagnetic complex [(1)W(CO)\(_3\)]Li·2THF (5). Compound 1 can also be reduced in the absence of a transition metal to its dianion 1\(^{2–}\), which possesses a quinoid-type structure. KW - half-sandwich complexes KW - transition metal complex KW - boron KW - redox reactions Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-156766 N1 - This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Journal of the American Chemical Society, copyright © 2017 American Chemical Society after peer review. To access the final edited and published work see dx.doi.org/10.1021/jacs.7b12394. ER - TY - INPR A1 - Stoy, Andreas A1 - Böhnke, Julian A1 - Jiménez-Halla, J. Oscar C. A1 - Dewhurst, Rian D. A1 - Thiess, Torsten A1 - Braunschweig, Holger T1 - CO\(_2\) Binding and Splitting by Boron–Boron Multiple Bonds T2 - Angewandte Chemie, International Edition N2 - CO\(_2\) is found to undergo room-temperature, ambient- pressure reactions with two species containing boron-boron multiple bonds, leading to incorporation of either one or two CO\(_2\) molecules. In one case, a thermally-unstable intermediate was structurally characterized, indicating the operation of an initial 2+2 cycloaddition mechanism in the reaction. KW - carbon dioxide KW - CO2 fixation KW - diborenes KW - diborynes KW - boron Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-164265 N1 - This is the pre-peer reviewed version of the following article: A. Stoy, J. Böhnke, J. O. C. Jiménez‐Halla, R. D. Dewhurst, T. Thiess, H. Braunschweig, Angew. Chem. Int.Ed. 2018, 57,5947 –5951, which has been published in final form at DOI: 10.1002/anie.201802117. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. ER - TY - INPR A1 - Arrowsmith, Merle A1 - Mattock, James D. A1 - Böhnke, Julian A1 - Krummenacher, Ivo A1 - Vargas, Alfredo A1 - Braunschweig, Holger T1 - Direct access to a cAAC-supported dihydrodiborene and its dianion T2 - Chemical Communications N2 - The two-fold reduction of (cAAC)BHX\(_2\) (cAAC = 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene; X = Cl, Br) provides a facile, high-yielding route to the dihydrodiborene (cAAC)\(_2\)B\(_2\)H\(_2\). The (chloro)hydroboryl anion reduction intermediate was successfully isolated using a crown ether. Overreduction of the diborene to its dianion [(cAAC)\(_2\)B\(_2\)H\(_2\)]\(^{2−}\) causes a decrease in the B–B bond order whereas the B–C bond orders increase. KW - carbenes KW - diborenes KW - boron KW - main-group chemistry KW - diborynes Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-164276 N1 - This is the pre-peer reviewed version of the following article: Chemical Communications, 2018, 54, 4669-4672 which has been published at DOI: 10.1039/C8CC01580E ER - TY - JOUR A1 - Böhnke, Julian A1 - Brückner, Tobias A1 - Hermann, Alexander A1 - González-Belman, Oscar F. A1 - Arrowsmith, Merle A1 - Jiménez-Halla, J. Oscar C. A1 - Braunschweig, Holger T1 - Single and double activation of acetone by isolobal B≡N and B≡B triple bonds JF - Chemical Science N2 - B≡N and B≡B triple bonds induce C-H activation of acetone to yield a (2-propenyloxy)aminoborane and an unsymmetrical 1-(2- propenyloxy)-2-hydrodiborene, respectively. DFT calculations showed that, despite their stark electronic differences, both the B≡N and B≡B triple bonds activate acetone via a similar coordination-deprotonation mechansim. In contrast, the reaction of acetone with a cAAC-supported diboracumulene yielded a unique 1,2,3-oxadiborole, which according to DFT calculations also proceeds via an unsymmetrical diborene, followed by intramolecular hydride migration and a second C-H activation of the enolate ligand. KW - acetone KW - diborynes KW - iminoboranes KW - boron KW - small-molecule activation Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-164286 VL - 9 ER - TY - INPR A1 - Cid, Jessica A1 - Hermann, Alexander A1 - Radcliffe, James E. A1 - Curless, Liam D. A1 - Braunschweig, Holger A1 - Ingleson, Michael J. T1 - Synthesis of Unsymmetrical Diboron(5) Compounds and Their Conversion to Diboron(5) Cations T2 - Organometallics N2 - Reaction of bis-catecholatodiboron-NHC adducts, B\(_2\)Cat\(_2\)(NHC), (NHC = IMe (tetramethylimidazol-2-ylidene), IMes (1,3-dimesitylimidazol-2-ylidene) or IDIPP (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene)) with BCl3 results in the replacement of the catecholato group bound to the four coordinate boron with two chlorides to yield diboron(5) Lewis acid-base adducts of formula CatB-BCl\(_2\)(NHC). These compounds are precursors to diboron(5) monocations, accessed by adding AlCl\(_3\) or K[B(C\(_6\)F\(_5\))\(_4\)] as halide abstraction agents in the presence of a Lewis base. The substitution of the chlorides of CatB-BCl\(_2\)(NHC) for hydrides is achieved using Bu\(_3\)SnH and a halide abstracting agent to form 1,1-dihydrodiboron(5) compounds, CatB-BH\(_2\)(NHC). Attempts to generate diboron(4) monocations of formula [CatB-B(Y)(NHC)]\(^+\) (Y = Cl or H) led to the rapid formation of CatBY. KW - diboron KW - boronium cations KW - boron KW - Lewis acids KW - electrophiles Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-164299 N1 - This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Organometallics, copyright © 2018 American Chemical Society after peer review. To access the final edited and published work see dx.doi.org/10.1021/acs.organomet.8b00288 ER - TY - INPR A1 - Böhnke, Julian A1 - Dellermann, Theresa A1 - Celik, Mehmet Ali A1 - Krummenacher, Ivo A1 - Dewhurst, Rian D. A1 - Demeshko, Serhiy A1 - Ewing, William C. A1 - Hammond, Kai A1 - Heß, Merlin A1 - Bill, Eckhard A1 - Welz, Eileen A1 - Röhr, Merle I. S. A1 - Mitric, Roland A1 - Engels, Bernd A1 - Meyer, Franc A1 - Braunschweig, Holger T1 - Isolation of diradical products of twisted double bonds T2 - Nature Communications N2 - Molecules containing multiple bonds between atoms—most often in the form of olefins—are ubiquitous in nature, commerce, and science, and as such have a huge impact on everyday life. Given their prominence, over the last few decades, frequent attempts have been made to perturb the structure and reactivity of multiply-bound species through bending and twisting. However, only modest success has been achieved in the quest to completely twist double bonds in order to homolytically cleave the associated π bond. Here, we present the isolation of double-bond-containing species based on boron, as well as their fully twisted diradical congeners, by the incorporation of attached groups with different electronic properties. The compounds comprise a structurally authenticated set of diamagnetic multiply-bound and diradical singly-bound congeners of the same class of compound. KW - diradicals KW - diborenes KW - carbenes KW - boron Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-160248 N1 - Submitted version of Julian Böhnke, Theresa Dellermann, Mehmet Ali Celik, Ivo Krummenacher, Rian D. Dewhurst, Serhiy Demeshko, William C. Ewing, Kai Hammond, Merlin Heß, Eckhard Bill, Eileen Welz, Merle I. S. Röhr, Roland Mitrić, Bernd Engels, Franc Meyer & Holger Braunschweig: Isolation of diborenes and their 90°-twisted diradical congeners. Nature Communications. Volume 9, Article number: 1197 (2018) doi:10.1038/s41467-018-02998-3 ER - TY - INPR A1 - Stennett, Tom A1 - Mattock, James A1 - Vollert, Ivonne A1 - Vargas, Alfredo A1 - Braunschweig, Holger T1 - Unsymmetrical, Cyclic Diborenes and Thermal Rearrangement to a Borylborylene T2 - Angewandte Chemie, International Edition N2 - Cyclic diboranes(4) based on a chelating monoanionic, benzylphosphine linker were prepared by boron-silicon exchange between arylsilanes and B\(_2\)Br\(_4\). Coordination of Lewis bases to the remaining sp\(^2\) boron atom yielded unsymmetrical sp\(^3\)-sp\(^3\) diboranes, which were reduced with KC\(_8\) to their corresponding trans-diborenes. These compounds were studied by a combination of spectroscopic methods, X-ray diffraction and DFT calculations. PMe\(_3\)-stabilized diborene 6 was found to undergo thermal rearrangement to gem- diborene 8. DFT calculations on 8 reveal a polar boron-boron bond, and indicate that the compound is best described as a borylborylene. KW - boron KW - borylene KW - multiple bonds KW - rearrangement KW - DFT calculations Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-160258 N1 - This is the pre-peer reviewed version of the following article: T. E. Stennett, J. D. Mattock, I. Vollert, A. Vargas, H. Braunschweig, Angew. Chem. Int. Ed. 2018, 57, 4098., which has been published in final form at DOI: 10.1002/anie.201800671. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. VL - 57 ER - TY - INPR A1 - Hermann, Alexander A1 - Cid, Jessica A1 - Mattock, James D. A1 - Dewhurst, Rian D. A1 - Krummenacher, Ivo A1 - Vargas, Alfredo A1 - Ingleson, Michael J. A1 - Braunschweig, Holger T1 - Diboryldiborenes: π‐Conjugated B\(_4\) Chains Isoelectronic to the Butadiene Dication T2 - Angewandte Chemie, International Edition N2 - sp\(^2\)–sp\(^3\) diborane species based on bis(catecholato)diboron and N-heterocyclic carbenes (NHCs) are subjected to catechol/bromide exchange selectively at the sp\(^3\) boron atom. The reduction of the resulting 1,1-dibromodiborane adducts led to reductive coupling and isolation of doubly NHC-stabilized 1,2-diboryldiborenes. These compounds are the first examples of molecules exhibiting pelectron delocalization over an all-boron chain. KW - diboranes KW - diborenes KW - N-heterocyclic carbenes KW - boron chains KW - pi-conjugation Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-167977 N1 - This is the pre-peer reviewed version of the following article: A. Hermann, J. Cid, J. D. Mattock, R. D. Dewhurst, I. Krummenacher, A. Vargas, M. J. Ingleson, H. Braunschweig, Angew. Chem. Int. Ed. 2018, 57, 10091, which has been published in final form at https://doi.org/10.1002/anie.201805394. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. ER - TY - INPR A1 - Böhnke, Julian A1 - Arrowsmith, Merle A1 - Braunschweig, Holger T1 - Activation of a Zerovalent Diboron Compound by Desymmetrization T2 - Journal of the American Chemical Society N2 - The desymmetrization of the cyclic (alkyl)(amino)carbene-supported diboracumulene, B\(_2\)(cAAC\(^{Me}\))\(_2\) (cAAC\(^{Me}\) = 1- (2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) by mono-adduct formation with IMe\(^{Me}\) (1,3-dimethylimidazol-2-ylidene) yields the zerovalent sp-sp\(^2\) diboron compound B\(_2\)(cAAC\(^{Me}\))\(_2\)(IMe\(^{Me}\)), which provides a versatile platform for the synthesis of novel symmetrical and unsymmetrical zerovalent sp\(^2\)-sp\(^2\) diboron compounds by adduct formation with IMe\(^{Me}\) and CO, respectively. Furthermore, B\(_2\)(cAAC\(^{Me}\))\(_2\)(IMe\(^{Me}\)) displays enhanced reactivity compared to its symmetrical precursor, undergoing spontaneous intramolecular C-H activation and facile twofold hydrogenation, the latter resulting in B-B bond cleavage and the formation of the mixed-base parent borylene, (cAAC\(^{Me}\))(IMe\(^{Me}\))BH. KW - diboryne KW - boron KW - carbenes KW - low-valent main group chemistry KW - erovalent diboron compounds KW - desymmetrization KW - bond activation KW - hydrogenation KW - borylene Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-167983 N1 - This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Journal of the American Chemical Society, copyright © American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/jacs.8b06930 (Julian Böhnke, Merle Arrowsmith, and Holger Braunschweig: Reactivity Enhancement of a Zerovalent Diboron Compound by Desymmetrization, Journal of the American Chemical Society 2018, 140, (32), 10368-10373. DOI: 10.1021/jacs.8b06930) ER - TY - INPR A1 - Stennett, Tom A1 - Mattock, James A1 - Pentecost, Leanne A1 - Vargas, Alfredo A1 - Braunschweig, Holger T1 - Chelated Diborenes and their Inverse-Electron-Demand Diels- Alder Reactions with Dienes T2 - Angewandte Chemie, International Edition N2 - A doubly base-stabilized diborane based on a benzylphosphine linker was prepared by a salt elimination reaction between 2-LiC\(_6\)H\(_4\)CH\(_2\)PCy\(_2\).Et\(_2\)O and B\(_2\)Br\(_4\). This compound was reduced with KC8 to its corresponding diborene, with the benzylphosphine forming a five-membered chelate. The diborene reacts with butadiene, 2-trimethylsiloxy-1,3-butadiene and isoprene to form 4,5-diboracyclohexenes, which interconvert between their 1,1- (geminal) and 1,2- (vicinal) chelated isomers. The 1,1-chelated diborene undergoes a halide-catalysed isomerisation into its thermodynamically favoured 1,2-isomer, which undergoes Diels-Alder reactions more slowly than the kinetic product. KW - boron KW - cycloaddition KW - DFT calculations KW - chelates KW - low-valent compounds Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-178268 N1 - This is the pre-peer reviewed version of the following article: T. E. Stennett, J. D. Mattock, L. Pentecost, A. Vargas, H. Braunschweig, Angew. Chem. Int. Ed. 2018, 57, 15276., which has been published in final form at https://doi.org/10.1002/anie.201809217. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. ER - TY - INPR A1 - Stennett, Tom A1 - Bertermann, Rüdiger A1 - Braunschweig, Holger T1 - Construction of Linear and Branched Tetraboranes via 1,1- and 1,2-Diboration of Diborenes T2 - Angewandte Chemie, International Edition N2 - Sterically unencumbered diborenes based on a benzylphosphine chelate undergo diboration reactions with bis(catecholato)diboron in the absence of a catalyst to yield tetraboranes. The symmetrical diborenes studied undergo 1,2- diborations, whereas an unsymmetrical derivative was found to yield a triborylborane-phosphine adduct as the result of a formal 1,1-diboration. A related borylborylene compound also underwent a 1,2-diboration to produce a borylene-borane adduct. KW - boron KW - diboration KW - chain structures KW - low-valent compounds KW - isomers Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-178276 N1 - This is the pre-peer reviewed version of the following article: T. E. Stennett, R. Bertermann, H. Braunschweig, Angew. Chem. Int. Ed. 2018, 57, 15896., which has been published in final form at https://doi.org/10.1002/anie.201809976. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. ER - TY - JOUR A1 - Böhnke, Julian A1 - Dellermann, Theresa A1 - Celik, Mehmet Ali A1 - Krummenacher, Ivo A1 - Dewhurst, Rian D. A1 - Demeshko, Serhiy A1 - Ewing, William C. A1 - Hammond, Kai A1 - Heß, Merlin A1 - Bill, Eckhard A1 - Welz, Eileen A1 - Röhr, Merle I. S. A1 - Mitric, Roland A1 - Engels, Bernd A1 - Meyer, Franc A1 - Braunschweig, Holger T1 - Isolation of diborenes and their 90°-twisted diradical congeners JF - Nature Communications N2 - Molecules containing multiple bonds between atoms—most often in the form of olefins—are ubiquitous in nature, commerce, and science, and as such have a huge impact on everyday life. Given their prominence, over the last few decades, frequent attempts have been made to perturb the structure and reactivity of multiply-bound species through bending and twisting. However, only modest success has been achieved in the quest to completely twist double bonds in order to homolytically cleave the associated π bond. Here, we present the isolation of double-bond-containing species based on boron, as well as their fully twisted diradical congeners, by the incorporation of attached groups with different electronic properties. The compounds comprise a structurally authenticated set of diamagnetic multiply-bound and diradical singly-bound congeners of the same class of compound. KW - chemical bonding KW - diradicals KW - organometallic chemistry KW - diborenes KW - carbenes KW - boron Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-160431 VL - 9 IS - Article number: 1197 ER - TY - JOUR A1 - Auerhammer, Dominic A1 - Arrowsmith, Merle A1 - Braunschweig, Holger A1 - Dewhurst, Rian D. A1 - Jiménez-Halla, J. Oscar C. A1 - Kupfer, Thomas T1 - Nucleophilic addition and substitution at coordinatively saturated boron by facile 1,2-hydrogen shuttling onto a carbene donor JF - Chemical Science N2 - The reaction of [(cAAC\(^{Me}\))BH\(_{3}\)] (cAAC\(^{Me}\) = 1-(2,6-iPr\(_{2}\)C\(_{6}\)H\(_{3}\))-3,3,5,5-tetramethylpyrrolidin-2-ylidene) with a range of organolithium compounds led to the exclusive formation of the corresponding (dihydro)organoborates, Li\(^{+}\)[(cAAC\(^{Me}\)H)BH\(_{2}\)R]− (R = sp\(^{3}\)-, sp\(^{2}\)-, or sp-hybridised organic substituent), by migration of one boron-bound hydrogen atom to the adjacent carbene carbon of the cAAC ligand. A subsequent deprotonation/salt metathesis reaction with Me3SiCl or spontaneous LiH elimination yielded the neutral cAAC-supported mono(organo)boranes, [(cAAC\(^{Me}\)H)BH\(_{2}\)R]− (R]. Similarly the reaction of [cAAC\(^{Me}\))BH\(_{3}\)] with a neutral donor base L resulted in adduct formation by shuttling one boron-bound hydrogen to the cAAC ligand, to generate [(cAAC\(^{Me}\)H)BH\(_{2}\)L], either irreversibly (L = cAAC\(^{Me}\)) or reversibly (L = pyridine). Variable-temperature NMR data and DFT calculations on [(cAAC\(^{Me}\)H)BH\(_{2}\)(cAAC\(^{Me}\))] show that the hydrogen on the former carbene carbon atom exchanges rapidly with the boron-bound hydrides. KW - nucleophilic addition KW - nucleophilic substitution KW - boron-bound hydrogen KW - carbene donor Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170255 VL - 8 IS - 10 ER - TY - INPR A1 - Auerhammer, Dominic A1 - Arrowsmith, Merle A1 - Bissinger, Philipp A1 - Braunschweig, Holger A1 - Dellermann, Theresa A1 - Kupfer, Thomas A1 - Lenczyk, Carsten A1 - Roy, Dipak A1 - Schäfer, Marius A1 - Schneider, Christoph T1 - Increasing the Reactivity of Diborenes: Derivatization of NHC- Supported Dithienyldiborenes with Electron-Donor Groups T2 - Chemistry, A European Journal N2 - 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. KW - diborenes KW - N-heterocyclic carbenes KW - electron donors KW - structural analysis KW - spectroscopy Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-155419 N1 - This is the pre-peer reviewed version of the following article: Auerhammer, D., Arrowsmith, M., Bissinger, P., Braunschweig, H., Dellermann, T., Kupfer, T., Lenczyk, C., Roy, D. K., Schäfer, M. and Schneider, C. (2017), Increasing the Reactivity of Diborenes: Derivatization of NHC-Supported Dithienyldiborenes with Electron-Donor Groups. Chem. Eur. J.. doi:10.1002/chem.201704669, which has been published in final form at doi:10.1002/chem.201704669. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. ER - TY - INPR A1 - Wang, Sunewang Rixin A1 - Arrowsmith, Merle A1 - Braunschweig, Holger A1 - Dewhurst, Rian A1 - Paprocki, Valerie A1 - Winner, Lena T1 - CuOTf-mediated intramolecular diborene hydroarylation T2 - Chemical Communications N2 - Upon complexation to CuOTf, a PMe\(_3\)-stabilized bis(9-anthryl) diborene slowly undergoes an intramolecular hydroarylation reaction at room temperature. Subsequent triflation of the B–H bond with CuOTf, followed by a PMe\(_3\) transfer, finally yields a cyclic sp\(^2\)-sp\(^3\) boryl-substituted boronium triflate salt. KW - boron KW - C-H activation KW - transition metals Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-154055 N1 - This is the pre-peer reviewed version of the following article: Chemical Communications, 2017, 11945-11947 which has been published at DOI: 10.1039/C7CC07371B. ER - TY - INPR A1 - Braunschweig, Holger A1 - Brückner, Tobias A1 - Deißenberger, Andrea A1 - Dewhurst, Rian A1 - Gackstatter, Annika A1 - Gärtner, Annalena A1 - Hofmann, Alexander A1 - Kupfer, Thomas A1 - Prieschl, Dominic A1 - Thiess, Torsten A1 - Wang, Sunewang Rixin T1 - Reaction of Dihalodiboranes(4) with N-Heterocyclic Silylenes: Facile Construction of 1-Aryl-2-Silyl-1,2-Diboraindanes T2 - Chemistry, A European Journal N2 - Dihalodiboranes(4) react with an N-heterocyclic silylene (NHSi) to generate NHSi-adducts of 1-aryl-2-silyl-1,2-diboraindanes as confirmed by X-ray crystallography, featuring the functionalization of both B–X (X = halogen) bonds and a C–H bond under mild conditions. Coordination of a third NHSi to the proposed 1,1-diaryl- 2,2-disilyldiborane(4) intermediates, generated by a two-fold B–X insertion, may be crucial for the C–H borylation that leads to the final products. Notably, our results demonstrate the first C–H borylation with a strong B–F bond activated by silylene insertion. KW - diborane KW - boron KW - silylenes KW - CH activation KW - bond activation KW - diboraindanes KW - diboranes KW - synthetic methods KW - borylation Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-153068 N1 - This is the pre-peer reviewed version of the following article: H. Braunschweig, T. Brückner, A. Deißenberger, R. D. Dewhurst, A. Gackstatter, A. Gärtner, A. Hofmann, T. Kupfer, D. Prieschl, T. Thiess, S. R. Wang, Reaction of Dihalodiboranes(4) with a N-Heterocyclic Silylene: Facile Construction of 1-Aryl-2-Silyl-1,2-Diboraindanes, Chem. Eur. J. 2017, 23, 9491., which has been published in final form at dx.doi.org/10.1002/chem.201702377. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving ER - TY - INPR A1 - Arrowsmith, Merle A1 - Böhnke, Julian A1 - Braunschweig, Holger A1 - Celik, Mehmet Ali T1 - Reactivity of a Dihydrodiborene with CO: Coordination, Insertion, Cleavage and Spontaneous Cyclic Alkyne Formation T2 - Angewandte Chemie, International Edition N2 - Under a CO atmosphere the dihydrodiborene [(cAAC)HB=BH(cAAC)] underwent coordination of CO concomitant with reversible hydrogen migration from boron to the carbene carbon atom, as well as reversible CO insertion into the B=B bond. Heating of the CO-adduct resulted in two unusual cAAC ring-expansion products, one presenting a B=C bond to a six-membered 1,2-azaborinane-3-ylidene, the other an unprecedented nine-membered cyclic alkyne resulting from reductive cleavage of CO and spontaneous C≡C triple bond formation. KW - CO activation KW - diborene KW - ring expansion KW - insertion KW - cyclic (alkyl)(amino)carbene Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-153318 N1 - This is the pre-peer reviewed version of the following article: Arrowsmith, M., Böhnke, J., Braunschweig, H. and Celik, M., Reactivity of a Dihydrodiborene with CO: Coordination, Insertion, Cleavage and Spontaneous Cyclic Alkyne Formation. Angew. Chem. Int. Ed. 2017, 129,14475 –14480. Accepted Author Manuscript. doi:10.1002/anie.201707907. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. ER - TY - INPR A1 - Wang, Sunewang R. A1 - Arrowsmith, Merle A1 - Böhnke, Julian A1 - Braunschweig, Holger A1 - Dellermann, Theresa A1 - Dewhurst, Rian D. A1 - Kelch, Hauke A1 - Krummenacher, Ivo A1 - Mattock, James D. A1 - Müssig, Jonas H. A1 - Thiess, Torsten A1 - Vargas, Alfredo A1 - Zhang, Jiji T1 - Engineering a Small HOMO-LUMO Gap and Intramolecular B–B Hydroarylation by Diborene/Anthracene Orbital Intercalation T2 - Angewandte Chemie, International Edition N2 - The diborene 1 was synthesized by reduction of a mixture of 1,2-di-9-anthryl-1,2-dibromodiborane(4) (6) and trimethylphosphine with potassium graphite. The X-ray structure of 1 shows the two anthryl rings to be parallel and their π(C\(_{14}\)) systems perpendicular to the diborene π(B=B) system. This twisted conformation allows for intercalation of the relatively high-lying π(B=B) orbital and the low-lying π* orbital of the anthryl moiety with no significant conjugation, resulting in a small HOMO-LUMO gap (HLG) and ultimately an unprecedented anthryl B–B bond hydroarylation. The HLG of 1 was estimated to be 1.57 eV from the onset of the long wavelength band in its UV–vis absorption spectrum (THF, λ\(_{onset}\) = 788 nm). The oxidation of 1 with elemental selenium afforded diboraselenirane 8 in quantitative yield. By oxidative abstraction of one phosphine ligand by another equivalent of elemental selenium, the B–B and C\(^1\)–H bonds of 8 were cleaved to give the cyclic 1,9-diboraanthracene 9. KW - boron KW - small HOMO-LUMO gap KW - diborenes KW - borylation KW - hydroarylation Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148126 N1 - This is the pre-peer reviewed version of the following article: S. R. Wang, M. Arrowsmith, J. Böhnke, H. Braunschweig, T. Dellermann, R. D. Dewhurst, H. Kelch, I. Krummenacher, J. D. Mattock, J. H. Müssig, T. Thiess, A. Vargas, J. Zhang, Angew. Chem. Int. Ed. 2017, 56, 8009., which has been published in final form at DOI: 10.1002/anie.201704063. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. VL - 56 IS - 27 ER - TY - INPR A1 - Arrowsmith, Merle A1 - Böhnke, Julian A1 - Braunschweig, Holger A1 - Deißenberger, Andrea A1 - Dewhurst, Rian A1 - Ewing, William A1 - Hörl, Christian A1 - Mies, Jan A1 - Muessig, Jonas T1 - Simple Solution-Phase Syntheses of Tetrahalodiboranes(4) and their Labile Dimethylsulfide Adducts T2 - Chemical Communications N2 - Convenient, solution-phase syntheses of tetrahalodiboranes(4) B\(_2\)F\(_4\), B\(_2\)Cl\(_4\) and B\(_2\)I\(_4\) are presented herein from common precursor B\(_2\)Br\(_4\). In addition, the dimethylsulfide adducts B\(_2\)Cl\(_4\)(SMe\(_2\))\(_2\) and B\(_2\)Br\(_4\)(SMe\(_2\))\(_2\) are conveniently prepared in one-step syntheses from the commercially-available starting material B\(_2\)(NMe\(_2\))\(_4\). The results provide simple access to the full range of tetrahalodiboranes(4) for the exploration of their untapped synthetic potential. KW - Boron KW - Diboranes KW - Tetrafluorodiborane Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149438 N1 - This is the pre-peer reviewed version of the following article: Chemical Communications, 2017,53, 8265-8267, which has been published in final form at doi:10.1039/C7CC03148C. VL - 53 ER - TY - INPR A1 - Arrowsmith, Merle A1 - Braunschweig, Holger A1 - Stennett, Tom T1 - Formation and Reactivity of Electron-Precise B–B Single and Multiple Bonds T2 - Angewandte Chemie, International Edition N2 - Recent years have seen rapid advances in the chemistry of small molecules containing electron-precise boron-boron bonds. This review provides an overview of the latest methods for the controlled synthesis of B–B single and multiple bonds as well as the ever-expanding range of reactivity displayed by the latter. KW - Boron KW - Main-group chemistry KW - Multiple bonding KW - Organoboron chemistry KW - Transition metals Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-145631 N1 - This is the pre-peer reviewed version of the following article: Angew.Chem. Int. Ed. 2017, 56,96–115, which has been published in final form at 10.1002/anie.201610072. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. N1 - Submitted Version VL - 56 IS - 1 ER - TY - INPR A1 - Wang, Sunewang Rixin A1 - Arrowsmith, Merle A1 - Braunschweig, Holger A1 - Dewhurst, Rian A1 - Dömling, Michael A1 - Mattock, James A1 - Pranckevicius, Conor A1 - Vargas, Alfredo T1 - Monomeric 16-Electron π-Diborene Complexes of Zn(II) and Cd(II) T2 - Journal of the American Chemical Society N2 - Despite the prevalence of stable π-complexes of most d\(^{10}\) metals, such as Cu(I) and Ni(0), with ethylene and other olefins, complexation of d\(^{10}\) Zn(II) to simple olefins is too weak to form isolable complexes due to the metal ion's limited capacity for π-backdonation. By employing more strongly donating π- ligands, namely neutral diborenes with a high-lying π(B=B) or- bital, monomeric 16-electron M(II)-diborene (M = Zn, Cd) π- complexes were synthesized in good yields. Metal–B2 π- interactions in both the solid and solution state were confirmed by single-crystal X-ray analyses and their solution NMR and UV-vis absorption spectroscopy, respectively. The M(II) centers adopt a trigonal planar geometry and interact almost symmetrically with both boron atoms. The MB2 planes significantly twist out of the MX\(_2\) planes about the M-centroid(B–B) vector, with angles rang- ing from 47.0° to 85.5°, depending on the steric interactions be- tween the diborene ligand and the MX\(_2\) fragment. KW - boron KW - transition metal complex KW - diborene Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-153058 N1 - This is the pre-peer reviewed version of the following article: Journal of the American Chemical Society, 2017, 139 (31), pp 10661–10664, which has been published in final form at doi:10.1021/jacs.7b06644. ER - TY - INPR A1 - Arrowsmith, Merle A1 - Böhnke, Julian A1 - Braunschweig, Holger A1 - Celik, Mehmet A1 - Claes, Christina A1 - Ewing, William A1 - Krummenacher, Ivo A1 - Lubitz, Katharina A1 - Schneider, Christoph T1 - Neutral Diboron Analogues of Archetypal Aromatic Species by Spontaneous Cycloaddition N2 - Among the numerous routes organic chemists have developed to synthesize benzene derivatives and heteroaro- matic compounds, transition-metal-catalyzed cycloaddition reactions are the most elegant. In contrast, cycloaddition reactions of heavier alkene and alkyne analogues, though limited in scope, proceed uncatalyzed. In this work we present the first spontaneous cycloaddition reactions of lighter alkene and alkyne analogues. Selective addition of unactivated alkynes to boron–boron multiple bonds under ambient con- ditions yielded diborocarbon equivalents of simple aromatic hydrocarbons, including the first neutral 6p-aromatic dibora- benzene compound, a 2 p-aromatic triplet biradical 1,3-dibor- ete, and a phosphine-stabilized 2 p-homoaromatic 1,3-dihydro- 1,3-diborete. DFT calculations suggest that all three com- pounds are aromatic and show frontier molecular orbitals matching those of the related aromatic hydrocarbons, C6H6 and C4H42+, and homoaromatic C4H5+. KW - Aromaticity KW - Biradicals KW - Boron KW - Cycloaddition KW - Multiple bonds KW - Diborane KW - Cycloaddition Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-142500 ER -