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 - THES A1 - Rempel, Anna T1 - Synthese und Reaktivität von Boryldiazenidokomplexen T1 - Synthesis and Reactivity of Boryldiazenido Complexes N2 - Die vorliegende Arbeit befasst sich mit der Synthese, Charakterisierung und Reaktivität von Boryldiazenidokomplexen. Im ersten Abschnitt wird die Synthese von neuartigen Boryldiazenidokomplexen behandelt. Im zweiten Teil werden Studien zu den Reaktivitäten dieser Verbindungen gegenüber Elektrophilen, Lewis-Basen sowie Reaktionen an den Element-Halogen-Bindungen vorgestellt. N2 - The present work deals with the synthesis, characterization and reactivity of boryldiazenido complexes. In the first section, the synthesis of novel boryldiazenido complexes is discussed. In the second part, studies on the reactivities of these compounds toward electrophiles, Lewis bases, and reactions at the element-halogen bonds are presented. KW - Übergangsmetallkomplexe KW - Diazenidokomplexe KW - Bor KW - Distickstoffkomplexe KW - Boryldiazenidokomplexe KW - Boryldiazenido Complexes Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-247415 ER - TY - JOUR A1 - Lindl, Felix A1 - Guo, Xueying A1 - Krummenacher, Ivo A1 - Rauch, Florian A1 - Rempel, Anna A1 - Paprocki, Valerie A1 - Dellermann, Theresa A1 - Stennett, Tom E. A1 - Lamprecht, Anna A1 - Brückner, Tobias A1 - Radacki, Krzysztof A1 - Bélanger-Chabot, Guillaume A1 - Marder, Todd B. A1 - Lin, Zhenyang A1 - Braunschweig, Holger T1 - Rethinking Borole Cycloaddition Reactivity JF - Chemistry—A European Journal N2 - Boroles are attracting broad interest for their myriad and diverse applications, including in synthesis, small molecule activation and functional materials. Their properties and reactivity are closely linked to the cyclic conjugated diene system, which has been shown to participate in cycloaddition reactions, such as the Diels-Alder reaction with alkynes. The reaction steps leading to boranorbornadienes, borepins and tricyclic boracyclohexenes from the thermal reaction of boroles with alkynes are seemingly well understood as judged from the literature. Herein, we question the long-established mechanistic picture of pericyclic rearrangements by demonstrating that seven-membered borepins (i. e., heptaphenylborepin and two derivatives substituted with a thienyl and chloride substituent on boron) exist in a dynamic equilibrium with the corresponding bicyclic boranorbornadienes, the direct Diels-Alder products, but are not isolable products from the reactions. Heating gradually converts the isomeric mixtures into fluorescent tricyclic boracyclohexenes, the most stable isomers in the series. Results from mechanistic DFT calculations reveal that the tricyclic compounds derive from the boranorbornadienes and not the borepins, which were previously believed to be intermediates in purely pericyclic processes. KW - pericyclic reaction KW - Boron KW - computational chemistry KW - isomer KW - isomerization Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256888 VL - 27 IS - 43 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 - 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 - JOUR A1 - Brückner, Tobias A1 - Heß, Merlin A1 - Stennett, Tom E. A1 - Rempel, Anna A1 - Braunschweig, Holger T1 - Synthesis of Boron Analogues of Enamines via Hydroamination of a Boron-Boron Triple Bond BT - Dedicated to Professor Wolfgang Kaim on the occasion of his 70th birthday JF - Angewandte Chemie, International Edition N2 - An N-heterocyclic-carbene-stabilized diboryne undergoes rapid, high-yielding and catalyst-free hydroamina- tion reactions with primary amines, yielding 1-amino-2-hydro- diborenes, which can be considered boron analogues of enamines. The electronics of the organic substituent at nitrogen influence the structure and further reactivity of the diborene product. With electron-rich anilines, a second hydroamination can occur at the diborene to generate 1,1-diamino-2,2-dihy- drodiboranes. With isopropylamine, the electronic influence of the alkyl substituent upon the diborene leads to an unprece- dented boron-mediated intramolecular N-dearylation reaction of an N-heterocyclic carbene unit. KW - boron KW - diborynes KW - diborenes KW - DFT KW - enamines KW - hydroamination KW - multiple bonds Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-240669 VL - 60 IS - 2 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 - Liu, Siyuan A1 - Légaré, Marc-André A1 - Seufert, Jens A1 - Prieschl, Dominic A1 - Rempel, Anna A1 - Englert, Lukas A1 - Dellermann, Theresa A1 - Paprocki, Valerie A1 - Stoy, Andreas A1 - Braunschweig, Holger T1 - 2,2′-Bipyridyl as a Redox-Active Borylene Abstraction Agent JF - Inorganic Chemistry N2 - 2,2′-Bipyridyl is shown to spontaneously abstract a borylene fragment (R–B:) from various hypovalent boron compounds. This process is a redox reaction in which the bipyridine is reduced and becomes a dianionic substituent bound to boron through its two nitrogen atoms. Various transition metal–borylene complexes and diboranes, as a well as a diborene, take part in this reaction. In the latter case, our results show an intriguing example of the homolytic cleavage of a B═B double bond. KW - Borylene KW - Heterocycles KW - Boron KW - Main-group chemistry Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-215595 N1 - This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Inorganic Chemistry, copyright © American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/acs.inorgchem.0c01383. VL - 59 IS - 15 ER - TY - JOUR A1 - Braunschweig, Holger A1 - Constantinidis, Philipp A1 - Dellermann, Theresa A1 - Ewing, William A1 - Fischer, Ingo A1 - Hess, Merlin A1 - Knight, Fergus A1 - Rempel, Anna A1 - Schneider, Christoph A1 - Ullrich, Stefan A1 - Vargas, Alfredo A1 - Woolins, Derek T1 - Highly Strained Heterocycles Constructed from Boron–Boron Multiple Bonds and Heavy Chalcogens JF - Angewandte Chemie, International Edition N2 - The reactions of a diborene with elemental selenium or tellurium are shown to afford a diboraselenirane or diboratellurirane, respectively. These reactions are reminiscent of the sequestration of subvalent oxygen and nitrogen in the formation of oxiranes and aziridines; however, such reactivity is not known between alkenes and the heavy chalcogens. Although carbon is too electronegative to affect the reduction of elements with lower relative electronegativity, the highly reducing nature of the B B double bond enables reactions with Se0 and Te0. The capacity of multiple bonds between boron atoms to donate electron density is highlighted in reactions where diborynes behave as nucleophiles, attacking one of the two Te atoms of diaryltellurides, forming salts consisting of diboratellurenium cations and aryltelluride anions. KW - Boron KW - Heterocycles KW - Multiple bonds KW - Selenium KW - Tellurium KW - Bor KW - Heterocyclische Verbindungen KW - Selen KW - Tellur Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-138237 N1 - This is the peer reviewed version of the following article: Angew. Chem. Int. Ed. 2016, 55, 5606–5609, which has been published in final form at 10.1002/anie.201601691. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. N1 - Accepted Version VL - 55 IS - 18 SP - 5606 EP - 5609 ER -