TY - JOUR A1 - Gärtner, Annalena A1 - Marek, Matthäus A1 - Arrowsmith, Merle A1 - Auerhammer, Dominic A1 - Radacki, Krzysztof A1 - Prieschl, Dominic A1 - Dewhurst, Rian D. A1 - Braunschweig, Holger T1 - Boron- versus Nitrogen-Centered Nucleophilic Reactivity of (Cyano)hydroboryl Anions: Synthesis of Cyano(hydro)organoboranes and 2-Aza-1,4-diborabutatrienes JF - Chemistry—A European Journal N2 - Cyclic alkyl(amino)carbene-stabilized (cyano)hydroboryl anions were synthesized by deprotonation of (cyano)dihydroborane precursors. While they display boron-centered nucleophilic reactivity towards organohalides, generating fully unsymmetrically substituted cyano(hydro)organoboranes, they show cyano-nitrogen-centered nucleophilic reactivity towards haloboranes, resulting in the formation of hitherto unknown linear 2-aza-1,4-diborabutatrienes. KW - nucleophile KW - boron KW - boryl anion KW - cumulene Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256853 VL - 27 IS - 37 ER - TY - JOUR A1 - Hagspiel, Stephan A1 - Arrowsmith, Merle A1 - Fantuzzi, Felipe A1 - Vargas, Alfredo A1 - Rempel, Anna A1 - Hermann, Alexander A1 - Brückner, Tobias A1 - Braunschweig, Holger T1 - Highly colored boron-doped thiazolothiazoles from the reductive dimerization of boron isothiocyanates JF - Angewandte Chemie International Edition N2 - Reduction of (CAAC)BBr\(_2\)(NCS) (CAAC=cyclic alkyl(amino)carbene) in the presence of a Lewis base L yields tricoordinate (CAAC)LB(NCS) borylenes which undergo reversible E/Z-isomerization. The same reduction in the absence of L yields deep blue, bis(CAAC)-stabilized, boron-doped, aromatic thiazolothiazoles resulting from the dimerization of dicoordinate (CAAC)B(NCS) borylene intermediates. KW - inorganic chemistry KW - aromaticity KW - reduction KW - fused thiazaboroles KW - DFT KW - borylenes Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256432 VL - 60 IS - 12 ER - TY - INPR A1 - Hermann, Alexander A1 - Arrowsmith, Merle A1 - Trujillo-Gonzalez, Daniel A1 - Jiménez-Halla, J. Oscar C. A1 - Vargas, Alfredo A1 - Braunschweig, Holger T1 - Trapping of a Borirane Intermediate in the Reductive Coupling of an Arylborane to a Diborene T2 - Journal of the American Chemical Society N2 - The reductive coupling of an NHC-stabilized aryldibromoborane yields a mixture of trans- and cis-diborenes in which the aryl groups are coplanar with the diborene core. Under dilute reduction conditions two diastereomers of a borirane-borane intermediate are isolated, which upon further reduction give rise to the aforementioned diborene mixture. DFT calculations suggest a mechanism proceeding via nucleophilic attack of a dicoordinate borylene intermediate on the aryl ring and subsequent intramolecular B-B bond formation. KW - boron KW - reactive intermediates KW - reductive coupling Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-203140 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.0c02306 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 - Lindl, Felix A1 - Lamprecht, Anna A1 - Arrowsmith, Merle A1 - Khitro, Eugen A1 - Rempel, Anna A1 - Dietz, Maximilian A1 - Wellnitz, Tim A1 - Bélanger‐Chabot, Guillaume A1 - Stoy, Andreas A1 - Paprocki, Valerie A1 - Prieschl, Dominik A1 - Lenczyk, Carsten A1 - Ramler, Jacqueline A1 - Lichtenberg, Crispin A1 - Braunschweig, Holger T1 - Aromatic 1,2‐Azaborinin‐1‐yls as Electron‐Withdrawing Anionic Nitrogen Ligands for Main Group Elements JF - Chemistry – A European Journal N2 - The 2‐aryl‐3,4,5,6‐tetraphenyl‐1,2‐azaborinines 1‐EMe\(_{3}\) and 2‐EMe\(_{3}\) (E=Si, Sn; aryl=Ph (1), Mes (=2,4,6‐trimethylphenyl, 2)) were synthesized by ring‐expansion of borole precursors with N\(_{3}\)EMe\(_{3}\)‐derived nitrenes. Desilylative hydrolysis of 1‐ and 2‐SiMe\(_{3}\) yielded the corresponding N‐protonated azaborinines, which were deprotonated with nBuLi or MN(SiMe\(_{3}\))\(_{2}\) (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 CO\(_{2}\) 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*=C\(_{5}\)Me\(_{5}\)), BBr\(_{2}\)Ar (Ar=Ph, Mes, 2‐thienyl), ECl\(_{3}\) (E=B, Al, Ga) and PX\(_{3}\) (X=Cl, Br) afforded the respective group 2, 13 and 15 1,2‐azaborinin‐2‐yl complexes. Salt metathesis of 1‐K with BBr\(_{3}\) resulted not only in N‐borylation but also Ph‐Br exchange between the endocyclic and exocyclic boron atoms. Solution \(^{11}\)B 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 C\(_{4}\)BN 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 \(^{11}\)B NMR resonances is linearly correlated to both the degree of twisting of the C\(_{4}\)BN 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. KW - 1,2-azaborinine KW - aromaticity KW - crystallographic analyses KW - N-functionalization KW - salt metathesis Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312222 VL - 29 IS - 11 ER - TY - JOUR A1 - Matler, Alexander A1 - Arrowsmith, Merle A1 - Schorr, Fabian A1 - Hermann, Alexander A1 - Hofmann, Alexander A1 - Lenczyk, Carsten A1 - Braunschweig, Holger T1 - Reactivity of Terminal Iron Borylenes and Bis(borylenes) with Carbodiimides: Cycloaddition, Metathesis, Insertion and C−H Activation Pathways JF - European Journal of Inorganic Chemistry N2 - The reactions of carbodiimides with the iron arylborylene complex [Fe=BDur(CO)\(_{3}\)(PMe\(_{3}\))] (Dur=2,3,5,6-Me\(_{4}\)C\(_{6}\)H) and the iron bis(borylene) complex [Fe{=BDur}{=BN(SiMe\(_{3}\))\(_{2}\)}(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. KW - structure elucidation KW - borylene complexes KW - cycloaddition KW - metathesis KW - reaction mechanisms Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-257397 VL - 2021 IS - 45 ER - TY - JOUR A1 - Rang, Maximilian A1 - Fantuzzi, Felipe A1 - Arrowsmith, Merle A1 - Krummenacher, Ivo A1 - Beck, Eva A1 - Witte, Robert A1 - Matler, Alexander A1 - Rempel, Anna A1 - Bischof, Tobias A1 - Radacki, Krzysztof A1 - Engels, Bernd A1 - Braunschweig, Holger T1 - Reduktion und Umlagerung eines Bor(I)‐Carbonylkomplexes JF - Angewandte Chemie N2 - Bei der Einelektronenreduktion eines durch eine cyclisches (Alkyl)(amino)carben (CAAC) stabilisierten Arylborylen-Carbonylkomplexes erfolgt die Bildung eines dimeren Borylketyl-Radikalanions, bedingt durch eine intramolekulare Arylmigration zum CO Kohlenstoffatom. Computergestützte Analyse liefert Hinweise auf eine radikalanionische [(CAAC)B(CO)Ar]\(^{.-}\) Zwischenstufe. Weiterführende Reduktion des entstandenen Komplexes liefert ein hoch nukleophiles (Boranyliden)methanolat. KW - Biradikale KW - Bor-Carbonylkomplexe KW - Dichtefunktionalrechnungen KW - Reduktionen KW - Umlagerungen Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224409 VL - 133 IS - 6 SP - 3000 EP - 3005 ER - TY - INPR A1 - Schmidt, Uwe A1 - Fantuzzi, Felipe A1 - Arrowsmith, Merle A1 - Hermann, Alexander A1 - Prieschl, Dominic A1 - Rempel, Anna A1 - Engels, Bernd A1 - Braunschweig, Holger T1 - Tuneable reduction of cymantrenylboranes to diborenes or borylene-derived boratafulvenes T2 - Chemical Communications N2 - Whereas the reduction of N-heterocyclic carbene (NHC)-stabilised cymantrenyldibromoboranes, (NHC)BBr\(_2\)Cym, in benzene results in formation of the corresponding diborenes (NHC)\(_2\)B\(_2\)Cym\(_2\), a change of solvent to THF yields a borylene of the form (NHC)\(_2\)BCym, stabilised through its boratafulvene resonance form. KW - Borylene KW - Diborene KW - Boranes Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-222149 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 - 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 - 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 - 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 - JOUR A1 - Witte, Robert A1 - Arrowsmith, Merle A1 - Lamprecht, Anna A1 - Schorr, Fabian A1 - Krummenacher, Ivo A1 - Braunschweig, Holger T1 - C−C and C−N Bond Activation, Lewis‐Base Coordination and One‐ and Two‐Electron Oxidation at a Linear Aminoborylene JF - Chemistry – A European Journal N2 - A cyclic alkyl(amino)carbene (CAAC)‐stabilized dicoordinate aminoborylene is synthesized by the twofold reduction of a [(CAAC)BCl\(_{2}\)(TMP)] (TMP=2,6‐tetramethylpiperidyl) precursor. NMR‐spectroscopic, X‐ray crystallographic and computational analyses confirm the cumulenic nature of the central C=B=N moiety. Irradiation of [(CAAC)B(TMP)] (2) resulted in an intramolecular C−C bond activation, leading to a doubly‐fused C\(_{10}\)BN heterocycle, while the reaction with acetonitrile resulted in an aryl migration from the CAAC to the acetonitrile nitrogen atom, concomitant with tautomerization of the latter to a boron‐bound allylamino ligand. One‐electron oxidation of 2 with CuX (X=Cl, Br) afforded the corresponding amino(halo)boryl radicals, which were characterized by EPR spectroscopy and DFT calculations. Placing 2 under an atmosphere of CO afforded the tricoordinate (CAAC,CO)‐stabilized aminoborylene. Finally, the twofold oxidation of 2 with chalcogens led, in the case of N\(_{2}\)O and sulfur, to the splitting of the B−C\(_{CAAC}\) bond and formation of the 2,4‐diamino‐1,3,2,4‐dichalcogenadiboretanes and CAAC‐chalcogen adducts, whereas with selenium a monomeric boraselenone was isolated, which showed some degree of B−Se multiple bonding. KW - bond activation KW - boraselenone KW - dicoordinate borylene KW - one-electron oxidation KW - push-pull stabilization Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312491 VL - 29 IS - 16 ER -