TY - JOUR A1 - Zhang, Fangyuan A1 - Radacki, Krzysztof A1 - Braunschweig, Holger A1 - Lambert, Christoph A1 - Ravat, Prince T1 - Zinc-[7]helicenocyanine and its discrete π-stacked homochiral Dimer JF - Angewandte Chemie International Edition N2 - In this communication, we demonstrate a novel approach to prepare a discrete dimer of chiral phthalocyanine (Pc) by exploiting the flexible molecular geometry of helicenes, which enables structural interlocking and strong aggregation tendency of Pcs. Synthesized [7]helicene-Pc hybrid molecular structure, zinc-[7]helicenocyanine (Zn-7HPc), exclusively forms a stable dimeric pair consisting of two homochiral molecules. The dimerization constants were estimated to be as high as 8.96×10\(^6\) M\(^{−1}\) and 3.42×107 M\(^{−1}\) in THF and DMSO, respectively, indicating remarkable stability of dimer. In addition, Zn\(^{-7}\)HPc exhibited chiral self-sorting behavior, which resulted in preferential formation of a homochiral dimer also in the racemic sample. Two phthalocyanine subunits in the dimeric form strongly communicate with each other as revealed by a large comproportionation constant and observation of an IV-CT band for the thermodynamically stable mixed-valence state. KW - organic chemistry KW - supramolecular assembly KW - chirality KW - helicenes KW - homochiral dimer KW - phthalocyanines Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256534 VL - 60 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 - TY - JOUR A1 - Weiser, Jonas A1 - Cui, Jingjing A1 - Dewhurst, Rian D. A1 - Braunschweig, Holger A1 - Engels, Bernd A1 - Fantuzzi, Felipe T1 - Structure and bonding of proximity‐enforced main‐group dimers stabilized by a rigid naphthyridine diimine ligand JF - Journal of Computational Chemistry N2 - The development of ligands capable of effectively stabilizing highly reactive main‐group species has led to the experimental realization of a variety of systems with fascinating properties. In this work, we computationally investigate the electronic, structural, energetic, and bonding features of proximity‐enforced group 13–15 homodimers stabilized by a rigid expanded pincer ligand based on the 1,8‐naphthyridine (napy) core. We show that the redox‐active naphthyridine diimine (NDI) ligand enables a wide variety of structural motifs and element‐element interaction modes, the latter ranging from isolated, element‐centered lone pairs (e.g., E = Si, Ge) to cases where through‐space π bonds (E = Pb), element‐element multiple bonds (E = P, As) and biradical ground states (E = N) are observed. Our results hint at the feasibility of NDI‐E2 species as viable synthetic targets, highlighting the versatility and potential applications of napy‐based ligands in main‐group chemistry. KW - bond theory KW - computational chemistry KW - density functional calculations KW - main group elements KW - N ligands Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312586 VL - 44 IS - 3 SP - 456 EP - 467 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 - 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 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 - 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 - Thiess, Torsten A1 - Ernst, Moritz A1 - Kupfer, Thomas A1 - Braunschweig, Holger T1 - Facile Access to Substituted 1,4‐Diaza‐2,3‐Diborinines JF - Chemistry – A European Journal N2 - Several bis(dimethylamino)‐substituted 1,4‐diaza‐2,3‐diborinines (DADBs) were synthesized with variable substituents at the backbone nitrogen atoms. By reaction with HCl or BX\(_{3}\) (X=Br, I), these species were successfully converted into their synthetically more useful halide congeners. The high versatility of the generated B−X bonds in further functionalization reactions at the boron centers was demonstrated by means of salt elimination (MeLi) and commutation (NMe\(_{2}\) DADBs) reactions, thus making the DADB system a general structural motif in diborane(4) chemistry. A total of 18 DADB derivatives were characterized in the solid state by X‐ray diffraction, revealing a strong dependence of the heterocyclic bonding parameters from the exocyclic substitution pattern at boron. According to our experiments towards the realization of a Dipp‐substituted, sterically encumbered DADB, the mechanism of DADB formation proceeds via a transient four‐membered azadiboretidine intermediate that subsequently undergoes ring expansion to afford the six‐membered DADB heterocycle. KW - azadiboretidines KW - B,N-heterocycles KW - diazadiborinines KW - diboranes KW - ring expansion Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-214650 VL - 26 IS - 13 SP - 2967 EP - 2972 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 - 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 - 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 - JOUR A1 - Stennett, Tom E. A1 - Jayaraman, Arumugam A1 - Brückner, Tobias A1 - Schneider, Lea A1 - Braunschweig, Holger T1 - Hydrophosphination of boron–boron multiple bonds JF - Chemical Science N2 - Five compounds containing boron–boron multiple bonds are shown to undergo hydrophosphination reactions with diphenylphosphine in the absence of a catalyst. With diborenes, the products obtained are highly dependent on the substitution pattern at the boron atoms, with both 1,1- and 1,2- hydrophosphinations observed. With a symmetrical diboryne, 1,2-hydrophosphination yields a hydro(phosphino)diborene. The different mechanistic pathways for the hydrophosphination of diborenes are rationalised with the aid of density functional theory calculations. KW - boron KW - diborenes KW - diborynes Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-240681 VL - 11 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 - 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 - Schorr, Fabian A1 - Schopper, Nils A1 - Riensch, Nicolas A1 - Fantuzzi, Felipe A1 - Neder, Marco A1 - Dewhurst, Rian D. A1 - Thiess, Thorsten A1 - Brückner, Tobias A1 - Hammond, Kai A1 - Helten, Holger A1 - Finze, Maik A1 - Braunschweig, Holger T1 - Controlled Synthesis of Oligomers Containing Main-Chain B(sp\(^{2}\))-B(sp\(^{2}\)) Bonds JF - Chemistry—A European Journal N2 - A number of novel alkynyl-functionalized diarylbis(dimethylamino)diboranes(4) are prepared by salt metathesis, and the appended alkynyl groups are subjected to hydroboration. Their reactions with monohydroboranes lead to discrete boryl-appended diborane(4) species, while dihydroboranes induce their catenation to oligomeric species, the first known examples of well-characterized macromolecular species with B−B bonds. The oligomeric species were found to comprise up to ten repeat units and are soluble in common organic solvents. Some of the oligomeric species have good air stability and all were characterized by NMR and vibrational spectroscopy and size-exclusion chromatography techniques. KW - oligomerization KW - boron KW - catenation KW - diborane KW - hydroboration Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-257274 VL - 27 IS - 64 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 - 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, Paul A1 - Fantuzzi, Felipe A1 - Klopf, Jonas A1 - Schröder, Niklas B. A1 - Dewhurst, Rian D. A1 - Braunschweig, Holger A1 - Engel, Volker A1 - Engels, Bernd T1 - Twisting versus delocalization in CAAC- and NHC-stabilized boron-based biradicals: the roles of sterics and electronics JF - Chemistry - A European Journal N2 - Twisted boron-based biradicals featuring unsaturated C\(_2\)R\(_2\) (R=Et, Me) bridges and stabilization by cyclic (alkyl)(amino)carbenes (CAACs) were recently prepared. These species show remarkable geometrical and electronic differences with respect to their unbridged counterparts. Herein, a thorough computational investigation on the origin of their distinct electrostructural properties is performed. It is shown that steric effects are mostly responsible for the preference for twisted over planar structures. The ground-state multiplicity of the twisted structure is modulated by the σ framework of the bridge, and different R groups lead to distinct multiplicities. In line with the experimental data, a planar structure driven by delocalization effects is observed as global minimum for R=H. The synthetic elusiveness of C\(_2\)R\(_2\)-bridged systems featuring N-heterocyclic carbenes (NHCs) was also investigated. These results could contribute to the engineering of novel main group biradicals. KW - chemistry KW - radicals KW - ab initio calculations KW - boron KW - carbene ligands KW - density functional calculations Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256636 VL - 27 IS - 16 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‐Stabilized 9,10‐diboraanthracenes—Acenes with Open‐Shell Singlet Biradical Ground States JF - Angewandte Chemie International Edition N2 - Narrow HOMO–LUMO gaps and high charge‐carrier mobilities make larger acenes potentially high‐efficient materials for organic electronic applications. The performance of such molecules was shown to significantly increase with increasing number of fused benzene rings. Bulk quantities, however, can only be obtained reliably for acenes up to heptacene. Theoretically, (oligo)acenes and (poly)acenes are predicted to have open‐shell singlet biradical and polyradical ground states, respectively, for which experimental evidence is still scarce. We have now been able to dramatically lower the HOMO–LUMO gap of acenes without the necessity of unfavorable elongation of their conjugated π system, by incorporating two boron atoms into the anthracene skeleton. Stabilizing the boron centers with cyclic (alkyl)(amino)carbenes gives neutral 9,10‐diboraanthracenes, which are shown to feature disjointed, open‐shell singlet biradical ground states. KW - acenes KW - biradicals KW - bond Activation KW - boron KW - heterocycles Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-217795 VL - 59 IS - 43 SP - 19338 EP - 19343 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 -