TY - JOUR A1 - He, Jiang A1 - Rauch, Florian A1 - Friedrich, Alexandra A1 - Krebs, Johannes A1 - Krummenacher, Ivo A1 - Bertermann, Rüdiger A1 - Nitsch, Jörn A1 - Braunschweig, Holger A1 - Finze, Maik A1 - Marder, Todd B. T1 - Phenylpyridyl-fused boroles: a unique coordination mode and weak B-N coordination-induced dual fluorescence JF - Angewandte Chemie International Edition N2 - Phenylpyridyl-fused boroles [TipPBB1]\(_4\) and TipPBB2 were synthesized and their properties investigated. [TipPBB1]\(_4\) forms a tetramer in both the solid state and solution. TipPBB2 contains a 4-coordinate boron atom in the solid state but dissociates to give a 3-coordinate boron species in solution. TipPBB2 shows interesting temperature-dependent dual fluorescence in solution because of the equilibrium between 3- and 4-coordinate boron species due to weak N⋅⋅⋅B intermolecular coordination. KW - inorganic chemistry KW - weak intermolecular coordination KW - boroles KW - dual fluorescence KW - equilibrium KW - tetramers Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256423 VL - 60 IS - 9 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 - 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 - Roy, Dipak Kumar A1 - Tröster, Tobias A1 - Fantuzzi, Felipe A1 - Dewhurst, Rian D. A1 - Lenczyk, Carsten A1 - Radacki, Krzysztof A1 - Pranckevicius, Conor A1 - Engels, Bernd A1 - Braunschweig, Holger T1 - Isolation and Reactivity of an Antiaromatic s‐Block Metal Compound JF - Angewandte Chemie International Edition N2 - The concepts of aromaticity and antiaromaticity have a long history, and countless demonstrations of these phenomena have been made with molecules based on elements from the p, d, and f blocks of the periodic table. In contrast, the limited oxidation‐state flexibility of the s‐block metals has long stood in the way of their participation in sophisticated π‐bonding arrangements, and truly antiaromatic systems containing s‐block metals are altogether absent or remain poorly defined. Using spectroscopic, structural, and computational techniques, we present herein the synthesis and authentication of a heterocyclic compound containing the alkaline earth metal beryllium that exhibits significant antiaromaticity, and detail its chemical reduction and Lewis‐base‐coordination chemistry. KW - antiaromaticity KW - aromaticity KW - beryllium KW - heterocycles KW - s-block metals Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224447 VL - 60 IS - 7 SP - 3812 EP - 3819 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 - 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 - Merz, Julia A1 - Dietrich, Lena A1 - Nitsch, Jörn A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Moos, Michael A1 - Mims, David A1 - Lambert, Christoph A1 - Marder, Todd B. T1 - Synthesis, Photophysical and Electronic Properties of Mono‐, Di‐, and Tri‐Amino‐Substituted Ortho‐Perylenes, and Comparison to the Tetra‐Substituted Derivative JF - Chemistry – A European Journal N2 - We synthesized a series of new mono‐, di‐, tri‐ and tetra‐substituted perylene derivatives with strong bis(para‐methoxyphenyl)amine (DPA) donors at the uncommon 2,5,8,11‐positions. The properties of our new donor‐substituted perylenes were studied in detail to establish a structure‐property relationship. Interesting trends and unusual properties are observed for this series of new perylene derivatives, such as a decreasing charge transfer (CT) character with increasing number of DPA moieties and individual reversible oxidations for each DPA moiety. Thus, (DPA)‐Per possesses one reversible oxidation while (DPA)\(_{4}\)‐Per has four. The mono‐ and di‐substituted derivatives display unusually large Stokes shifts not previously reported for perylenes. Furthermore, transient absorption measurements of the new derivatives reveal an excited state with lifetimes of several hundred microseconds, which sensitizes singlet oxygen with quantum yields of up to 0.83. KW - borylation KW - intersystem crossing KW - luminescence KW - polycyclic aromatic hydrocarbon KW - triarylamine Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-217835 VL - 26 IS - 52 SP - 12050 EP - 12059 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 - 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 - 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 - 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 - 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 - 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 - 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 - JOUR A1 - Ewing, William C. A1 - Dellermann, Theresa A1 - Angel Wong, Y. T. A1 - Mattock, James D. A1 - Vargas, Alfredo A1 - Bryce, David L. A1 - Dewhurst, Rian D. A1 - Braunschweig, Holger T1 - \(\pi\)‐Complexes of Diborynes with Main Group Atoms JF - Chemistry – An Asian Journal N2 - We present herein an in‐depth study of complexes in which a molecule containing a boron‐boron triple bond is bound to tellurate cations. The analysis allows the description of these salts as true π complexes between the B−B triple bond and the tellurium center. These complexes thus extend the well‐known Dewar‐Chatt‐Duncanson model of bonding to compounds made up solely of p block elements. Structural, spectroscopic and computational evidence is offered to argue that a set of recently reported heterocycles consisting of phenyltellurium cations complexed to diborynes bear all the hallmarks of \(\pi\)‐complexes in the \(\pi\)‐complex/metallacycle continuum envisioned by Joseph Chatt. Described as such, these compounds are unique in representing the extreme of a metal‐free continuum with conventional unsaturated three‐membered rings (cyclopropenes, azirenes, borirenes) occupying the opposite end. KW - boron KW - main group elements KW - solid-state NMR KW - \(\pi\) interactions KW - multiple bonds Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-214677 VL - 15 IS - 10 SP - 1553 EP - 1557 ER - TY - JOUR A1 - Brunecker, Carina A1 - Müssig, Jonas H. A1 - Arrowsmith, Merle A1 - Fantuzzi, Felipe A1 - Stoy, Andreas A1 - Böhnke, Julian A1 - Hofmann, Alexander A1 - Bertermann, Rüdiger A1 - Engels, Bernd A1 - Braunschweig, Holger T1 - Boranediyl‐ and Diborane(4)‐1,2‐diyl‐Bridged Platinum A‐Frame Complexes JF - Chemistry – A European Journal N2 - Diplatinum A‐frame complexes with a bridging (di)boron unit in the apex position were synthesized in a single step by the double oxidative addition of dihalo(di)borane precursors at a bis(diphosphine)‐bridged Pt\(^{0}\)\(_{2}\) complex. While structurally analogous to well‐known μ‐borylene complexes, in which delocalized dative three‐center‐two‐electron M‐B‐M bonding prevails, theoretical investigations into the nature of Pt−B bonding in these A‐frame complexes show them to be rare dimetalla(di)boranes displaying two electron‐sharing Pt−B σ‐bonds. This is experimentally reflected in the low kinetic stability of these compounds, which are prone to loss of the (di)boron bridgehead unit. KW - boron KW - bonding KW - EDA-NOCV KW - oxidative addition KW - platinum Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-214707 VL - 26 IS - 39 SP - 8518 EP - 8523 ER - TY - JOUR A1 - Braunschweig, Holger A1 - Krummenacher, Ivo A1 - Mailänder, Lisa A1 - Pentecost, Leanne A1 - Vargas, Alfredo T1 - Formation of a stable radical by oxidation of a tetraorganoborate JF - Chemical Communications N2 - Herein, we describe the selective formation of a stable neutral spiroborate radical by one-electron oxidation of the corresponding tetraorganoborate salt Li[B(C\(_4\)Ph\(_4\))\(_2\)], formally containing a tetrahedral borate centre and a s-cis-butadiene radical cation as the spin-bearing site. Spectroscopic and computational methods have been used to determine the spin distribution and the chromism observed in the solid state. KW - tetraorganoborate salt KW - spiroborates KW - one-electron oxidation KW - spin distribution KW - chromism Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191321 VL - 52 IS - 43 ER - TY - JOUR A1 - Braunschweig, Holger A1 - Ewing, William C. A1 - Ghosh, Sundargopal A1 - Kramer, Thomas A1 - Mattock, James D. A1 - Östreicher, Sebastian A1 - Vargas, Alfredo A1 - Werner, Christine T1 - Trimetallaborides as starting points for the syntheses of large metal-rich molecular borides and clusters JF - Chemical Science N2 - Treatment of an anionic dimanganaborylene complex ([{Cp(CO)\(_2\)Mn}\(_2\)B]\(^-\)) with coinage metal cations stabilized by a very weakly coordinating Lewis base (SMe\(_2\)) led to the coordination of the incoming metal and subsequent displacement of dimethylsulfide in the formation of hexametalladiborides featuring planar four-membered M\(_2\)B\(_2\) cores (M = Cu, Au) comparable to transition metal clusters constructed around four-membered rings composed solely of coinage metals. The analogies between compounds consisting of B\(_2\)M\(_2\) units and M\(_4\) (M = Cu, Au) units speak to the often overlooked metalloid nature of boron. Treatment of one of these compounds (M = Cu) with a Lewis-basic metal fragment (Pt(PCy\(_3\))\(_2\)) led to the formation of a tetrametallaboride featuring two manganese, one copper and one platinum atom, all bound to boron in a geometry not yet seen for this kind of compound. Computational examination suggests that this geometry is the result of d\(^{10}\)-d\(^{10}\) dispersion interactions between the copper and platinum fragments. KW - anionic dimetalloborylene complexes KW - trimetallaborides KW - tetrametallaborides KW - Boron KW - metallaboranes KW - crystal structure KW - metal borylene complexes Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191511 VL - 7 IS - 1 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 - 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 - 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 - 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 - 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 - 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 - Merz, Julia A1 - Dietz, Maximilian A1 - Vonhausen, Yvonne A1 - Wöber, Frederik A1 - Friedrich, Alexandra A1 - Sieh, Daniel A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Moos, Michael A1 - Holzapfel, Marco A1 - Lambert, Christoph A1 - Marder, Todd B. T1 - Synthesis, Photophysical and Electronic Properties of New Red-to-NIR Emitting Donor-Acceptor Pyrene Derivatives JF - Chemistry - A European Journal N2 - We synthesized new pyrene derivatives with strong bis(para ‐methoxyphenyl)amine donors at the 2,7‐positions and n ‐azaacene acceptors at the K‐region of pyrene. The compounds possess a strong intramolecular charge transfer, leading to unusual properties such as emission in the red to NIR region (700 nm), which has not been reported before for monomeric pyrenes. Detailed photophysical studies reveal very long intrinsic lifetimes of >100 ns for the new compounds, which is typical for 2,7‐substituted pyrenes but not for K‐region substituted pyrenes. The incorporation of strong donors and acceptors leads to very low reduction and oxidation potentials, and spectroelectrochemical studies show that the compounds are on the borderline between localized Robin‐Day class‐II and delocalized Robin‐Day class‐III species. KW - orylation KW - K-region KW - luminescence KW - polycyclic aromatic hydrocarbons KW - redox Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-207486 VL - 26 IS - 2 ER - TY - JOUR A1 - Horrer, Günther A1 - Krahfuß, Mirjam J. A1 - Lubitz, Katharina A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Radius, Udo T1 - N-Heterocyclic Carbene and Cyclic (Alkyl)(amino)carbene Complexes of Titanium(IV) and Titanium(III) JF - European Journal of Inorganic Chemistry N2 - The reaction of one and two equivalents of the N ‐heterocyclic carbene IMes [IMes = 1,3‐bis(2,4,6‐trimethyl‐phenyl)imidazolin‐2‐ylidene] or the cyclic (alkyl)(amino)carbene cAAC\(^{Me}\) [cAAC\(^{Me}\) = 1‐(2,6‐diisopropyl‐phenyl)‐3,3,5,5‐tetra‐methylpyrrolidin‐2‐ylidene] with [TiCl\(_{4}\)] in n ‐hexane results in the formation of mono‐ and bis‐carbene complexes [TiCl\(_{4}\)(IMes)] 1 , [TiCl\(_{4}\)(IMes)2] 2 , [TiCl\(_{4}\)(cAAC\(^{Me}\))] 3 , and [TiCl\(_{4}\)(cAAC\(^{Me}\))\(_{2}\)] 4 , respectively. For comparison, the titanium(IV) NHC complex [TiCl\(_{4}\)(Ii Pr\(^{Me}\))] 5 (Ii Pr\(^{Me}\) = 1,3‐diisopropyl‐4,5‐dimethyl‐imidazolin‐2‐ylidene) has been synthesized and structurally characterized. The reaction of [TiCl\(_{4}\)(IMes)] 1 with PMe\(_{3}\) affords the mixed substituted complex [TiCl\(_{4}\)(IMes)(PMe\(_{3}\))] 6 . The reactions of [TiCl\(_{3}\)(THF)\(_{3}\)] with two equivalents of the carbenes IMes and cAAC\(^{Me}\) in n ‐hexane lead to the clean formation of the titanium(III) complexes [TiCl\(_{3}\)(IMes)\(_{2}\)] 7 and [TiCl\(_{3}\)(cAAC\(^{Me}\))\(_{2}\)] 8 . Compounds 1 –8 have been completely characterized by elemental analysis, IR and multinuclear NMR spectroscopy and for 2 –5 , 7 and 8 by X‐ray diffraction. Magnetometry in solution, EPR and UV/Vis spectroscopy and DFT calculations performed on 7 and 8 are indicative of a predominantly metal‐centered d\(^{1}\)‐radical in both cases. KW - N-heterocyclic carbenes KW - carbene ligands KW - Titanium KW - structure elucidation Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-208725 VL - 2020 IS - 3 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 - 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 - 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 - 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 - Ansell, Melvyn B. A1 - Kostakis, George E. A1 - Braunschweig, Holger A1 - Navarro, Oscar A1 - Spencer, John T1 - Synthesis of functionalized hydrazines: facile homogeneous (N-heterocyclic carbene)-palladium(0)-catalyzed diboration and silaboration of azobenzenes JF - Advanced Synthesis & Catalysis N2 - The bis(N-heterocyclic carbene)(diphenylacetylene)palladium complex Pd(ITMe)\(_2\)(PhCCPh)] (ITMe=1,3,4,5-tetramethylimidazol-2-ylidene) acts as a highly active pre-catalyst in the diboration and silaboration of azobenzenes to synthesize a series of novel functionalized hydrazines. The reactions proceed using commercially available diboranes and silaboranes under mild reaction conditions. KW - Palladium-catalyzed silaboration KW - B-B bond KW - molecular-structure KW - terminal alkynes KW - crystal-structure KW - alkenes KW - complexes KW - mechanism KW - boron KW - design KW - azobenzenes KW - dilaboration KW - N-heterocyclic carbenes KW - palladium KW - silaboration Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-186582 VL - 358 IS - 23 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 - 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 - JOUR A1 - Arnold, Thomas A1 - Braunschweig, Holger A1 - Gruss, Katrin T1 - cyclo-Tri-mu-oxido-tris{[(eta 5,eta 5)-1,2-bis(cyclopentadienyl)-1,1,2,2-tetramethyldisilane]zirconium(IV)}: a trimeric disila-bridged oxidozirconocene JF - Acta Crystallographica Section E: metal-organic compounds N2 - The title compound, [Zr(3)(C(14)H(20)Si(2))(3)O(3)], consists of three disila-bridged zirconocene units, which are connected via an oxide ligand, forming a nearly planar six-membered ring with a maximum displacement of 0.0191 (8) A. The compound was isolated as a by-product from a mixture of [(C(5)H(4)SiMe(2))(2)ZrCl(2)] and Li[AlH(4)] in Et(2)O. KW - Kristallographie Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-134802 VL - 67 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 - 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 - 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 JF - Angewandte Chemie, International Edition 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 6 π-aromatic dibora- benzene compound, a 2  π-aromatic triplet biradical 1,3-dibor- ete, and a phosphine-stabilized 2  π-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, C\(_6\)H\(_6\) and C\(_4\)H\(_4\)\(^{2+}\), and homoaromatic C\(_4\)H\(_5\)\(^+\). KW - Aromaticity KW - Biradicals KW - Boron KW - Cycloaddition KW - Multiple bonds Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-138226 N1 - This is the peer reviewed version of the following article: Angew. Chem. Int. Ed. 2016, 55, 11271–11275, which has been published in final form at 10.1002/anie.201602384. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. VL - 55 ER - TY - JOUR A1 - Arrowsmith, Merle A1 - Böhnke, Julian A1 - Braunschweig, Holger A1 - Celik, Mehmet A1 - Dellermann, Theresa A1 - Hammond, Kai T1 - Uncatalyzed Hydrogenation of First-Row Main Group Multiple Bonds JF - Chemistry, A European Journal N2 - Room temperature hydrogenation of an SIDep-stabilized diboryne (SIDep = 1,3-bis(diethylphenyl)-4,5-dihydroimidazol-2-ylidene) and a CAAC-supported diboracumulene (CAAC = 1-(2,6- diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) provided the first selective route to the corresponding 1,2-dihydrodiborenes. DFT calculations showed an overall exothermic (ΔG = 19.4 kcal mol\(^{-1}\) two-step asynchronous H\(_2\) addition mechanism proceeding via a bridging hydride. KW - diborenes KW - carbenes KW - hydrogenation KW - main-group chemistry KW - reaction mechanism KW - Diborane Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-139364 N1 - This is the peer reviewed version of the following article: Chemistry, A European Journal, 2016, 22, 17169–17172, which has been published in final form at 10.1002/chem.201604094. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. VL - 22 IS - 48 SP - 17169 EP - 17172 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 - TY - JOUR A1 - Arnold, Nicole A1 - Braunschweig, Holger A1 - Damme, Alexander T1 - Bis(μ-diisopropyl-phosphanido-\(κ^2\)P:P)bis-[hydrido(triisopropyl-phosphane-κP)platinum(II)] JF - Acta crystallographica. Section E, Structure reports online N2 - In the centrosymmetric molecular structure of the title compound \([Pt_2(C_6H_{14}P)_2H_2)(C_9H_{21}P)_2]\), each \(Pt^{II}\) atom is bound on one side to a phosphane ligand \((PiPr_3)\) and a hydrido ligand. On the other side, it is bound to two phosphanide ligands \((μ-PiPr_2)\), which engage a bridging position between the two \(Pt^{II}\) atoms, forming a distorted square-planar structure motif. The PtPt distance is 3.6755(2)Å. A comparable molecular structure was observed for bis-(μ-di-tert-butyl-phosphanido)bis-[hydrido(triethyl-phosphane)platinum(II)] [Itazaki et al. (2004 ). Organometallics, 23, 1610-1621]. KW - data-to-parameter ratio = 22.3 KW - mean σ(C–C) = 0.004 Å KW - single-crystal X-ray study KW - T = 100 K KW - R factor = 0.018 KW - wR factor = 0.038 Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-123723 VL - E68 ER - TY - JOUR A1 - Braunschweig, Holger A1 - Kramer, T. T1 - Crystal structure of μ-1κC:2(\(η^2\))-carbonyl-carbonyl-1κC-chlorido-2κCl-μ-chloridoborylene-1:2\(κ^2\) B:B-[1(\(η^5\))-pentamethylcyclopentadienyl](tricyclohexylphosphane-2κP)iron(II)platinum(II) benzene monosolvate N2 - In the mol­ecular structure of the dinuclear title compound \([η^5-(C_5(CH_3)_5)(CO)Fe{(μ-BCl)(μ-CO)}PtCl(P(C_6H_{11})_3)]·C_6H_6\), the two metal atoms, iron(II) and platinum(II), are bridged by one carbonyl (μ-CO) and one chlorido­borylene ligand (μ-BCl). The \(Pt^{II}\) atom is additionally bound to a chloride ligand situated trans to the bridging borylene, and a tri­cyclo­hexyl­phosphane ligand \((PCy_3)\) trans to the carbonyl ligand, forming a distorted square-planar structural motif at the \(Pt^{II}\) atom. The \(Fe_{II}\) atom is bound to a penta­methyl­cyclo­penta­dienyl ligand \([η^5-C_5(CH_3)_5]\) and one carbonyl ligand (CO), forming a piano-stool structure. Additionally, one benzene solvent mol­ecule is incorporated into the crystal structure, positioned staggered relative to the penta­methyl­cyclo­penta­dienyl ligand at the \(Fe^{II}\) atom, with a centroid–centroid separation of 3.630 (2) Å. KW - platinum KW - oxidative addition KW - borylene KW - heterodinuclear compound KW - crystal structure Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-120120 VL - 70 IS - 11 ER - TY - JOUR A1 - Braunschweig, Holger A1 - Arnold, Thomas A1 - Gruss, Katrin T1 - cyclo-Tri-mu-oxido-tris{[(eta 5,eta 5)-1,2-bis(cyclopentadienyl)-1,1,2,2-tetramethyldisilane]zirconium(IV)}: atrimeric disila-bridged oxidozirconocene N2 - no abstract available KW - Chemie KW - single-crystal X-ray study KW - T = 174 K KW - R factor = 0.027 KW - wR factor = 0.069 KW - data-to-parameter ratio = 23.6. Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-74737 ER - TY - JOUR A1 - Braunschweig, Holger A1 - Damme, Alexander T1 - 1,2-Bis(dimethylamino)-1,2-bis(2,4,6-triisopropylphenyl)diborane(4) N2 - In the molecular structure of the title compound, C34H58B2N2, each B atom of the diborane(4) is connected to one dimethylamino group and one Tip ligand (Tip = 2,4,6-triisopropylphenyl). These findings indicate that the increased steric demand of the Tip groups exerts influence solely on the B—B separation but not on the overall geometry of the title compound. KW - Anorganische Chemie Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-67639 ER - TY - JOUR A1 - Braunschweig, Holger A1 - Dewhurst, Rian D. A1 - Schwab, Katrin A1 - Wagner, Katharina T1 - {N ',N ''-Bis[2,6-bis(1-methylethyl)phenyl]-N,N-dimethylguanidinato-kappa N-2 ',N ''}dibromidoborane N2 - In the molecular structure of the title compound, C27H40N3BBr2, the B atom is connected to two bromide substituents and a guanidinate scaffold, forming a four– membered ring. An aryl group is connected to each N atom in the ring that contains two isopropyl groups in positions 2 and 6. KW - Anorganische Chemie Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-67622 ER -