TY - JOUR A1 - Riensch, Nicolas Alexander A1 - Swoboda, Lukas A1 - Lik, Artur A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Helten, Holger T1 - Conjugated Bis(triarylboranes) with Disconnected Conjugation JF - Zeitschrift für anorganische und allgemeine Chemie N2 - A series of methylene-bridged bis(triarylboranes) has been synthesized via two complementary routes using metal-free catalytic Si/B exchange condensation under mild conditions. The title compounds comprise two borane moieties that show effective internal π-conjugation involving the respective boron centers and the adjacent hetaryl groups. Conjugation between both borane units, however, is disrupted by the aliphatic linker. Cyclic voltammetry revealed minimal electronic communication between the boron centers, as evidenced by two closely spaced reduction processes. The UV-vis spectra showed bathochromic shifted absorption bands compared to related monoboranes, which is attributed to the methylene bridge. A further red-shift results upon introduction of methyl or SiMe\(_3\) groups at the terminal thiophene rings. KW - Boron KW - thiophene KW - conjugated oligomers KW - hybrid materials KW - boranes Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-258020 VL - 647 IS - 5 ER - TY - JOUR A1 - Bachmann, Jonas A1 - Helbig, Andreas A1 - Crumbach, Merian A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Helten, Holger T1 - Fusion of Aza‐ and Oxadiborepins with Furans in a Reversible Ring‐Opening Process Furnishes Versatile Building Blocks for Extended π‐Conjugated Materials JF - Chemistry – A European Journal N2 - A modular synthesis of both difurooxa‐ and difuroazadiborepins from a common precursor is demonstrated. Starting from 2,2′‐bifuran, after protection of the positions 5 and 5’ with bulky silyl groups, formation of the novel polycycles proceeds through opening of the furan rings to a dialkyne and subsequent re‐cyclization in the borylation step. The resulting bifuran‐fused diborepins show pronounced stability, highly planar tricyclic structures, and intense blue light emission. Deprotection and transformation into dibrominated building blocks that can be incorporated into π‐extended materials can be performed in one step. Detailed DFT calculations provide information about the aromaticity of the constituent rings of this polycycle. KW - aromaticity KW - boron KW - BN compounds KW - furan KW - polycycles Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-293926 VL - 28 IS - 63 ER - TY - JOUR A1 - Crumbach, Merian A1 - Bachmann, Jonas A1 - Fritze, Lars A1 - Helbig, Andreas A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Helten, Holger T1 - Dithiophene‐Fused Oxadiborepins and Azadiborepins: A New Class of Highly Fluorescent Heteroaromatics JF - Angewandte Chemie International Edition N2 - Access to dithiophene‐fused oxadiborepins and the first azadiborepins attained via a modular synthesis route are presented. The new compounds emit intense blue light, some of which demonstrate fluorescence quantum yields close to unity. Cyclic voltammetry (CV) revealed electrochemically reversible one‐electron reduction processes. The weak aromatic character of the novel 1,2,7‐azadiborepin ring is demonstrated with in‐depth theoretical investigations using nucleus‐independent chemical shift (NICS) scans and anisotropy of the induced current density (ACID) calculations. KW - aromaticity KW - BN compounds KW - boron KW - isoelectronic analogues KW - polycycles Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-238996 VL - 60 IS - 17 SP - 9290 EP - 9295 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 - 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 - 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 - 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 - 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 - 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 - 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 - Braunschweig, Holger A1 - Krummenacher, Ivo A1 - Lichtenberg, Crispin A1 - Mattock, James A1 - Schäfer, Marius A1 - Schmidt, Uwe A1 - Schneider, Christoph A1 - Steffenhagen, Thomas A1 - Ullrich, Stefan A1 - Vargas, Alfredo T1 - Dibora[2]ferrocenophane: A Carbene-Stabilized Diborene in a Strained cis-Configuration T2 - Angewandte Chemie, International Edition N2 - Unsaturated bridges that link the two cyclopentadienyl ligands together in strained ansa metallocenes are rare and limited to carbon-carbon double bonds. The synthesis and isolation of a strained ferrocenophane containing an unsaturated two-boron bridge, isoelectronic with a C=C double bond, was achieved by reduction of a carbene-stabilized 1,1’-bis(dihaloboryl)ferrocene. A combination of spectroscopic and electrochemical measurements as well as density functional theory (DFT) calculations was used to assess the influence of the unprecedented strained cis configuration on the optical and electrochemical properties of the carbene-stabilized diborene unit. Initial reactivity studies show that the dibora[2]ferrocenophane is prone to boron-boron double bond cleavage reactions. KW - Boron KW - Metallocenes KW - Metallocene KW - Bor KW - Diborane KW - density functional calculations KW - strained molecules KW - diborenes Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-141981 N1 - This is the pre-peer reviewed version of the following article: Angewandte Chemie, International Edition, Volume 56, Issue 3, 889–892, which has been published in final form at doi:10.1002/anie.201609601. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. ER -