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  - 
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  - 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  - 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  - 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  - 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  - 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  - INPR
A1  - Hermann, Alexander
A1  - Arrowsmith, Merle
A1  - Trujillo-Gonzalez, Daniel
A1  - Jiménez-Halla, J. Oscar C.
A1  - Vargas, Alfredo
A1  - Braunschweig, Holger
T1  - Trapping of a Borirane Intermediate in the Reductive Coupling of an Arylborane to a Diborene
T2  - Journal of the American Chemical Society
N2  - The reductive coupling of an NHC-stabilized aryldibromoborane yields a mixture of trans- and cis-diborenes in which the aryl groups are coplanar with the diborene core. Under dilute reduction conditions two diastereomers of a borirane-borane intermediate are isolated, which upon further reduction give rise to the aforementioned diborene mixture. DFT calculations suggest a mechanism proceeding via nucleophilic attack of a dicoordinate borylene intermediate on the aryl ring and subsequent intramolecular B-B bond formation.
KW  - boron
KW  - reactive intermediates
KW  - reductive coupling
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-203140
N1  - This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Journal of the American Chemical Society, copyright © American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/jacs.0c02306
ER  - 
TY  - JOUR
A1  - Schmidt, Uwe
A1  - Werner, Luis
A1  - Arrowsmith, Merle
A1  - Deissenberger, Andrea
A1  - Hermann, Alexander
A1  - Hofmann, Alexander
A1  - Ullrich, Stefan
A1  - Mattock, James D.
A1  - Vargas, Alfredo
A1  - Braunschweig, Holger
T1  - Trans‐selektive Dihydroborierung eines cis‐Diborens durch Insertion: Synthese eines linearen sp\(^3\)‐sp\(^2\)‐sp\(^3\)‐Triborans und anschließende Kationisierung
JF  - Angewandte Chemie
N2  - Die Reaktion zwischen Aryl‐ und Amino(dihydro)boranen und Dibora[2]ferrocenophan 1 führt zur Bildung von 1,3‐trans‐Dihydrotriboranen durch formale Hydrierung und Insertion eines Borylens in die B=B Doppelbindung. Die Aryltriboran‐Derivate unterliegen einer reversiblen Photoisomerisierung zugunsten eines cis‐1,2‐μ‐H‐3‐Hydrotriborans, während eine Hydridabstraktion zu kationischen Triboranen führt, welche die ersten doppelt basenstabilisierten B\(_3\)H\(_4\)\(^+\)‐Analoga darstellen.
KW  - Diboren
KW  - Hydroborierung
KW  - Kation
KW  - Photoisomerisierung
KW  - Triboran
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-219713
VL  - 132
IS  - 1
ER  - 
TY  - JOUR
A1  - Schmidt, Uwe
A1  - Werner, Luis
A1  - Arrowsmith, Merle
A1  - Deissenberger, Andrea
A1  - Hermann, Alexander
A1  - Hofmann, Alexander
A1  - Ullrich, Stefan
A1  - Mattock, James D.
A1  - Vargas, Alfredo
A1  - Braunschweig, Holger
T1  - trans-Selective Insertional Dihydroboration of a cis-Diborene: Synthesis of Linear sp\(^3\)-sp\(^2\)-sp\(^3\)-Triboranes and Subsequent Cationization
JF  - Angewandte Chemie International Edition
N2  - The reaction of aryl‐ and amino(dihydro)boranes with dibora[2]ferrocenophane 1 leads to the formation 1,3‐trans ‐dihydrotriboranes by formal hydrogenation and insertion of a borylene unit into the B=B bond. The aryltriborane derivatives undergo reversible photoisomerization to the cis ‐1,2‐μ‐H‐3‐hydrotriboranes, while hydride abstraction affords cationic triboranes, which represent the first doubly base‐stabilized B3H4\(^+\) analogues.
KW  - cations
KW  - hydroboration
KW  - photoisomerization
KW  - triboranes
KW  - diborenes
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-208090
VL  - 59
IS  - 1
ER  - 
TY  - 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  - Ramler, Jaqueline
A1  - Fantuzzi, Felipe
A1  - Geist, Felix
A1  - Hanft, Anna
A1  - Braunschweig, Holger
A1  - Engels, Bernd
A1  - Lichtenberg, Crispin
T1  - The dimethylbismuth cation: entry into dative Bi-Bi bonding and unconventional methyl exchange
JF  - Angewandte Chemie International Edition
N2  - The dimethyl bismuth cation, [BiMe\(_2\)(SbF\(_6\))], has been isolated and characterized. Reaction with BiMe\(_3\) allows access to the first compound featuring Bi→Bi donor–acceptor bonding. In solution, dynamic behavior with methyl exchange via an unusual S\(_E\)2 mechanism is observed, underlining the unique properties of bismuth species as soft Lewis acids with the ability to undergo reversible Bi−C bond cleavage.
KW  - inorganic chemistry
KW  - methyl exchange
KW  - bismuth
KW  - cationic species
KW  - electrophilic substitution
KW  - Lewis acidity
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256543
VL  - 60
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  - 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  - 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  - 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  - Brückner, Tobias
A1  - Arrowsmith, Merle
A1  - Heß, Merlin
A1  - Hammond, Kai
A1  - Müller, Marcel
A1  - Braunschweig, Holger
T1  - Synthesis of fused B,N-heterocycles by alkyne cleavage, NHC ring-expansion and C-H activation at a diboryne
T2  - Chemical Communications
N2  - The addition of alkynes to a staturated N-heterocyclic carbene (NHC)-supported diboryne results in spontaneous cycloaddition, with complete B≡B and C≡C triple bond cleavage, NHC ring- expansion and activation of a variety of C-H bonds, leading to the formation of complex mixtures of fused B,N-heterocycles.
KW  - heterocycles
KW  - alkynes
KW  - boron
KW  - carbenes
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-184899
N1  - This is the pre-peer reviewed version of the following article: Chem. Commun., 2019,55, 6700-6703, which has been published in final form at doi:10.1039/C9CC02657F
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  - 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  - Krebs, Johannes
A1  - Haehnel, Martin
A1  - Krummenacher, Ivo
A1  - Friedrich, Alexandra
A1  - Braunschweig, Holger
A1  - Finze, Maik
A1  - Ji, Lei
A1  - Marder, Todd B.
T1  - Synthesis and Structure of an o-Carboranyl-Substituted Three-Coordinate Borane Radical Anion
JF  - Chemistry—A European Journal
N2  - Bis(1-(4-tolyl)-carboran-2-yl)-(4-tolyl)-borane [(1-(4-MeC\(_{6}\)H\(_{4}\))-closo-1,2-C\(_{2}\)B\(_{10}\)H\(_{10}\)-2-)\(_{2}\)(4-MeC\(_{6}\)H\(_{4}\))B] (1), a new bis(o-carboranyl)-(R)-borane was synthesised by lithiation of the o-carboranyl precursor and subsequent salt metathesis reaction with (4-tolyl)BBr\(_{2}\). Cyclic voltammetry experiments on 1 show multiple distinct reduction events with a one-electron first reduction. In a selective reduction experiment the corresponding paramagnetic radical anion 1\(^{.−}\) was isolated and characterized. Single-crystal structure analyses allow an in-depth comparison of 1, 1\(^{.−}\), their calculated geometries, and the S\(_{1}\) excited state of 1. Photophysical studies of 1 show a charge transfer (CT) emission with low quantum yield in solution but a strong increase in the solid state. TD-DFT calculations were used to identify transition-relevant orbitals.
KW  - Wade’s rules
KW  - carborane
KW  - charge transfer
KW  - radical
KW  - threecoordinate boron
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256841
VL  - 27
IS  - 31
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  - 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  - Dietz, Maximilian
A1  - Arrowsmith, Merle
A1  - Reichl, Stephan
A1  - Lugo‐Fuentes, Leonardo I.
A1  - Jiménez‐Halla, J. Oscar C.
A1  - Scheer, Manfred
A1  - Braunschweig, Holger
T1  - Stable Two‐Legged Parent Piano‐Stool and Mixed Diborabenzene‐E\(_{4}\) (E=P, As) Sandwich Complexes of Group 8
JF  - Angewandte Chemie International Edition
N2  - A cyclic alkyl(amino)carbene‐stabilized 1,4‐diborabenzene (DBB) ligand enables the isolation of 18‐electron two‐legged parent piano‐stool Fe\(^{0}\) and Ru\(^{0}\) complexes, [(η\(^{6}\)‐DBB)M(CO)\(_{2}\)], the ruthenium complex being the first of its kind to be structurally characterized. [(η\(^{6}\)‐DBB)Fe(CO)\(_{2}\)] reacts with E\(_{4}\) (E=P, As) to yield mixed DBB‐cyclo‐E\(_{4}\) sandwich complexes with planar E\(_{4}\)\(^{2-}\) ligands. Computational analyses confirm the strong electron‐donating capacity of the DBB ligand and show that the E\(_{4}\) ligand is bound by four equivalent Fe−P σ bonds.
KW  - 1,4-Diborabenzene
KW  - bonding
KW  - group 8 metals
KW  - Parent Piano-Stool Complex
KW  - Pnictogen reduction
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-293880
VL  - 61
IS  - 36
ER  - 
TY  - INPR
A1  - Englert, Lukas
A1  - Stoy, Andreas
A1  - Arrowsmith, Merle
A1  - Müssig, Jonas H.
A1  - Thaler, Melanie
A1  - Deißenberger, Andrea
A1  - Häfner, Alena
A1  - Böhnke, Julian
A1  - Hupp, Florian
A1  - Seufert, Jens
A1  - Mies, Jan
A1  - Damme, Alexander
A1  - Dellermann, Theresa
A1  - Hammond, Kai
A1  - Kupfer, Thomas
A1  - Radacki, Krzysztof
A1  - Thiess, Torsten
A1  - Braunschweig, Holger
T1  - Stable Lewis Base Adducts of Tetrahalodiboranes: Synthetic Methods and Structural Diversity
T2  - Chemistry - A European Journal
N2  - A series of 22 new bis(phosphine), bis(carbene) and bis(isonitrile) tetrahalodiborane adducts has been synthesized, either by direct adduct formation with highly sensitive B2X4 precursors (X = Cl, Br, I) or by ligand exchange at stable B2X4(SMe2)2 precursors (X = Cl, Br) with labile dimethylsulfide ligands. The isolated compounds have been fully characterized using NMR spectroscopic, (C,H,N)- elemental and, for 20 of these compounds, X-ray crystallographic analysis, revealing an unexpected variation in the bonding motifs. Besides the classical B2X4L2 diborane(6) adducts, some of the more sterically demanding carbene ligands induce a halide displacement leading to the first halide-bridged monocationic diboron species, [B2X3L2]A (A = BCl4, Br, I). Furthermore, low-temperature 1:1 reactions of B2Cl4 with sterically demanding N-heterocyclic carbenes led to the formation of kinetically unstable mono-adducts, one of which was structurally characterized. A comparison of the NMR and structural data of new and literature-known bis-adducts shows several trends pertaining to the nature of the halides and the stereoelectronic properties of the Lewis bases employed.
KW  - diborane(6)
KW  - Lewis-base adducts
KW  - ligand exchange
KW  - crystallography
KW  - NMR spectroscopy
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-184888
N1  - This is the pre-peer reviewed version of the following article: L. Englert, A. Stoy, M. Arrowsmith, J. H. Muessig, M. Thaler, A. Deißenberger, A. Häfner, J. Böhnke, F. Hupp, J. Seufert, J. Mies, A. Damme, T. Dellermann, K. Hammond, T. Kupfer, K. Radacki, T. Thiess, H. Braunschweig, Chem. Eur. J. 2019, 25, 8612. https://doi.org/10.1002/chem.201901437, which has been published in final form at https://doi.org/10.1002/chem.201901437. 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  - Nees, Samuel
A1  - Kupfer, Thomas
A1  - Hofmann, Alexander
A1  - Braunschweig, Holger
T1  - Stabilisierung planarer Cyclopenten‐4‐yl‐Kationen durch Hyperkonjugation und π‐Delokalisierung
JF  - Angewandte Chemie
N2  - Theoretischen Untersuchungen zufolge stellt das planare Cyclopenten-4-yl-Kation das energetisch ungünstigste C\(_{5}\)H\(_{7}\)\(^{+}\)-Isomer dar und ist am ehesten als klassisches Carbokation zu beschreiben, wobei dessen Existenz experimentell bislang noch nicht nachgewiesen werden konnte. Durch Umsetzung sterisch überfrachteter Alane vom Typ Cp\(^{R}\)AlBr\(_{2}\) mit AlBr3 ist uns nun die Isolierung zweier stabiler Derivate des Cyclopenten-4-yl-Kations gelungen. Untersuchungen zu deren (elektronischer) Struktur (XRD, QM) offenbarten planare Geometrien und starke Hyperkonjugationswechselwirkungen zwischen den C-Al-σ-Bindungen und dem unbesetzten p-Orbital der kationischen sp\(^{2}\)-Kohlenstoffzentren. Die Analyse der Molekülorbitale (MOs), der Anisotropie der induzierten Stromdichte (ACID) sowie verschiedener Aromatizitätsdeskriptoren deuten hierbei auf ein hohes Maß an Delokalisierung und π-Aromatizität in diesen Systemen hin, was einer klassischen Beschreibung grundlegend widerspricht. Unsere Cyclopenten-4-yl-Kationen gehören somit zu den wenigen Beispielen aromatischer Carbocyclen, in denen eine Delokalisierung der π-Elektronen über gesättigte sp\(^{3}\)-Kohlenstoffatome hinweg beobachtet wird.
KW  - ACID
KW  - Carbokationen
KW  - Cyclopenten-4-yl-Kation
KW  - Hyperkonjugation
KW  - π-Aromatizität
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218456
VL  - 132
IS  - 42
SP  - 18971
EP  - 18978
ER  - 
TY  - INPR
A1  - Arrowsmith, Merle
A1  - Dömling, Michael
A1  - Schmidt, Uwe
A1  - Werner, Luis
A1  - Castro, Abril C.
A1  - Jiménez-Halla, J. Oscar C.
A1  - Müssig, Jonas
A1  - Prieschl, Dominic
A1  - Braunschweig, Holger
T1  - Spontaneous trans‐Selective Transfer Hydrogenation of Apolar B=B Double Bonds
T2  - Angewandte Chemie, International Edition
N2  - The transfer hydrogenation of NHC-supported diborenes with dimethylamine borane proceeds with high selectivity for the trans-1,2-dihydrodiboranes(6). DFT calculations suggest a stepwise proton-first-hydride-second reaction mechanism via an intermediate μ-hydrodiboronium dimethylaminoborate ion pair.
KW  - transfer hydrogenation
KW  - diborene
KW  - amine borane dehydrocoupling
KW  - diboranes
KW  - DFT mechanism
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-184874
N1  - This is the pre-peer reviewed version of the following article: M. Dömling, M. Arrowsmith, U. Schmidt, L. Werner, A. C. Castro, J. O. C. Jiménez-Halla, R. Bertermann, J. Müssig, D. Prieschl, H. Braunschweig, Angew. Chem. Int. Ed. 2019, 58, 9782. doi:10.1002/anie.201902656, which has been published in final form at  https://doi.org/10.1002/anie.201902656. 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  - Brückner, Tobias
A1  - Stennett, Tom E.
A1  - Heß, Merlin
A1  - Braunschweig, Holger
T1  - Single and Double Hydroboration of B-B Triple Bonds and Conver- gent Routes to a Cationic Tetraborane
T2  - Journal of the American Chemical Society
N2  - A compound with a boron-boron triple bond is shown to undergo stepwise hydroboration reactions with catecholborane to yield an unsymmetrical hydro(boryl)diborene and a 2,3-dihydrotetraborane. Abstraction of H– from the latter compound produces an unusual cationic, planar tetraborane with a hydrogen atom bridging the central B2 moiety. Spectroscopic and crystallographic data and DFT calculations support a ‘protonated diborene’ structure for this compound, which can also be accessed via direct protonation of the corresponding diborene.
KW  - boron
KW  - multiple bonding
KW  - hydroboration
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-188632
N1  - This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Journal of the American Chemical Society, copyright © American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/jacs.9b07991.
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  - Arrowsmith, Merle
A1  - Böhnke, Julian
A1  - Braunschweig, Holger
A1  - Deißenberger, Andrea
A1  - Dewhurst, Rian
A1  - Ewing, William
A1  - Hörl, Christian
A1  - Mies, Jan
A1  - Muessig, Jonas
T1  - Simple Solution-Phase Syntheses of Tetrahalodiboranes(4) and their Labile Dimethylsulfide Adducts
T2  - Chemical Communications
N2  - Convenient, solution-phase syntheses of tetrahalodiboranes(4) B\(_2\)F\(_4\), B\(_2\)Cl\(_4\) and B\(_2\)I\(_4\) are presented herein from common precursor B\(_2\)Br\(_4\). In addition, the dimethylsulfide adducts B\(_2\)Cl\(_4\)(SMe\(_2\))\(_2\) and B\(_2\)Br\(_4\)(SMe\(_2\))\(_2\) are conveniently prepared in one-step syntheses from the commercially-available starting material B\(_2\)(NMe\(_2\))\(_4\). The results provide simple access to the full range of tetrahalodiboranes(4) for the exploration of their untapped synthetic potential.
KW  - Boron
KW  - Diboranes
KW  - Tetrafluorodiborane
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149438
N1  - This is the pre-peer reviewed version of the following article: Chemical Communications, 2017,53, 8265-8267, which has been published in final form at doi:10.1039/C7CC03148C.
VL  - 53
ER  - 
TY  - JOUR
A1  - Heß, Merlin
A1  - Krummenacher, Ivo
A1  - Dellermann, Theresa
A1  - Braunschweig, Holger
T1  - Rhodium-Mediated Stoichiometric Synthesis of Mono-, Bi-, and Bis-1,2-Azaborinines: 1-Rhoda-3,2-azaboroles as Reactive Precursors
JF  - Chemistry—A European Journal
N2  - A series of highly substituted 1,2-azaborinines, including a phenylene-bridged bis-1,2-azaborinine, was synthesized from the reaction of 1,2-azaborete rhodium complexes with variously substituted alkynes. 1-Rhoda-3,2-azaborole complexes, which are accessible by phosphine addition to the corresponding 1,2-azaborete complexes, were also found to be suitable precursors for the synthesis of 1,2-azaborinines and readily reacted with alkynyl-substituted 1,2-azaborinines to generate new regioisomers of bi-1,2-azaborinines, which feature directly connected aromatic rings. Their molecular structures, which can be viewed as boron-nitrogen isosteres of biphenyls, show nearly perpendicular 1,2-azaborinine rings. The new method using rhodacycles instead of 1,2-azaborete complexes as precursors is shown to be more effective, allowing the synthesis of a wider range of 1,2-azaborinines.
KW  - structure elucidation
KW  - azaborinines
KW  - nitrogen heterocycles
KW  - cyclization
KW  - metallacycles
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256830
VL  - 27
IS  - 37
ER  - 
TY  - JOUR
A1  - Lindl, Felix
A1  - Guo, Xueying
A1  - Krummenacher, Ivo
A1  - Rauch, Florian
A1  - Rempel, Anna
A1  - Paprocki, Valerie
A1  - Dellermann, Theresa
A1  - Stennett, Tom E.
A1  - Lamprecht, Anna
A1  - Brückner, Tobias
A1  - Radacki, Krzysztof
A1  - Bélanger-Chabot, Guillaume
A1  - Marder, Todd B.
A1  - Lin, Zhenyang
A1  - Braunschweig, Holger
T1  - Rethinking Borole Cycloaddition Reactivity
JF  - Chemistry—A European Journal
N2  - Boroles are attracting broad interest for their myriad and diverse applications, including in synthesis, small molecule activation and functional materials. Their properties and reactivity are closely linked to the cyclic conjugated diene system, which has been shown to participate in cycloaddition reactions, such as the Diels-Alder reaction with alkynes. The reaction steps leading to boranorbornadienes, borepins and tricyclic boracyclohexenes from the thermal reaction of boroles with alkynes are seemingly well understood as judged from the literature. Herein, we question the long-established mechanistic picture of pericyclic rearrangements by demonstrating that seven-membered borepins (i. e., heptaphenylborepin and two derivatives substituted with a thienyl and chloride substituent on boron) exist in a dynamic equilibrium with the corresponding bicyclic boranorbornadienes, the direct Diels-Alder products, but are not isolable products from the reactions. Heating gradually converts the isomeric mixtures into fluorescent tricyclic boracyclohexenes, the most stable isomers in the series. Results from mechanistic DFT calculations reveal that the tricyclic compounds derive from the boranorbornadienes and not the borepins, which were previously believed to be intermediates in purely pericyclic processes.
KW  - pericyclic reaction
KW  - Boron
KW  - computational chemistry
KW  - isomer
KW  - isomerization
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256888
VL  - 27
IS  - 43
ER  - 
TY  - JOUR
A1  - Rang, Maximilian
A1  - Fantuzzi, Felipe
A1  - Arrowsmith, Merle
A1  - Krummenacher, Ivo
A1  - Beck, Eva
A1  - Witte, Robert
A1  - Matler, Alexander
A1  - Rempel, Anna
A1  - Bischof, Tobias
A1  - Radacki, Krzysztof
A1  - Engels, Bernd
A1  - Braunschweig, Holger
T1  - Reduktion und Umlagerung eines Bor(I)‐Carbonylkomplexes
JF  - Angewandte Chemie
N2  - Bei der Einelektronenreduktion eines durch eine cyclisches (Alkyl)(amino)carben (CAAC) stabilisierten Arylborylen-Carbonylkomplexes erfolgt die Bildung eines dimeren Borylketyl-Radikalanions, bedingt durch eine intramolekulare Arylmigration zum CO Kohlenstoffatom. Computergestützte Analyse liefert Hinweise auf eine radikalanionische [(CAAC)B(CO)Ar]\(^{.-}\) Zwischenstufe. Weiterführende Reduktion des entstandenen Komplexes liefert ein hoch nukleophiles (Boranyliden)methanolat.
KW  - Biradikale
KW  - Bor-Carbonylkomplexe
KW  - Dichtefunktionalrechnungen
KW  - Reduktionen
KW  - Umlagerungen
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224409
VL  - 133
IS  - 6
SP  - 3000
EP  - 3005
ER  - 
TY  - JOUR
A1  - Matler, Alexander
A1  - Arrowsmith, Merle
A1  - Schorr, Fabian
A1  - Hermann, Alexander
A1  - Hofmann, Alexander
A1  - Lenczyk, Carsten
A1  - Braunschweig, Holger
T1  - Reactivity of Terminal Iron Borylenes and Bis(borylenes) with Carbodiimides: Cycloaddition, Metathesis, Insertion and C−H Activation Pathways
JF  - European Journal of Inorganic Chemistry
N2  - The reactions of carbodiimides with the iron arylborylene complex [Fe=BDur(CO)\(_{3}\)(PMe\(_{3}\))] (Dur=2,3,5,6-Me\(_{4}\)C\(_{6}\)H) and the iron bis(borylene) complex [Fe{=BDur}{=BN(SiMe\(_{3}\))\(_{2}\)}(CO)\(_{3}\)] yield a wide variety of temperature-dependent products, including known FeBNC and novel FeBNB metallacycles, complexes of N-heterocyclic boracarbene and spiro-boracarbene ligands and a unique 1,3,2,4-diazadiborolyl pianostool complex, characterized by NMR spectroscopy and X-ray crystallography. The product distributions can be rationalized by considering sequences of cycloaddition, metathesis, insertion, and C−H activation pathways mainly governed by sterics.
KW  - structure elucidation
KW  - borylene complexes
KW  - cycloaddition
KW  - metathesis
KW  - reaction mechanisms
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-257397
VL  - 2021
IS  - 45
ER  - 
TY  - 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  - 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  - JOUR
A1  - Arrowsmith, Merle
A1  - Endres, Sara
A1  - Heinz, Myron
A1  - Nestler, Vincent
A1  - Holthausen, Max C.
A1  - Braunschweig, Holger
T1  - Probing the Boundaries between Lewis-Basic and Redox Behavior of a Parent Borylene
JF  - Chemistry—A European Journal
N2  - The parent borylene (CAAC)(Me\(_{3}\)P)BH, 1 (CAAC=cyclic alkyl(amino)carbene), acts both as a Lewis base and one-electron reducing agent towards group 13 trichlorides (ECl\(_{3}\), E=B, Al, Ga, In), yielding the adducts 1-ECl\(_{3}\) and increasing proportions of the radical cation [1]\(^{•+}\) for the heavier group 13 analogues. With boron trihalides (BX\(_{3}\), X=F, Cl, Br, I) 1 undergoes sequential adduct formation and halide abstraction reactions to yield borylboronium cations and shows an increasing tendency towards redox processes for the heavier halides. Calculations confirm that 1 acts as a strong Lewis base towards EX3 and show a marked increase in the B−E bond dissociation energies down both group 13 and the halide group.
KW  - redox processes
KW  - bond dissociation energies
KW  - borylene
KW  - group 13
KW  - Lewis adducts
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-257154
VL  - 27
IS  - 70
ER  - 
TY  - JOUR
A1  - Brunecker, Carina
A1  - Arrowsmith, Merle
A1  - Fantuzzi, Felipe
A1  - Braunschweig, Holger
T1  - Platin‐vermittelte Kupplung von B=N‐Einheiten: Synthese von BNBN‐Analoga von 1,3‐Dienen und Butatrien
JF  - Angewandte Chemie
N2  - Die 1:2-Reaktion von [μ-(dmpm)Pt(nbe)]\(_{2}\) (dmpm=Bis(dimethylphosphino)methan, nbe=Norbornen) mit Cl\(_{2}\)BNR(SiMe\(_{3}\)) (R=tBu, SiMe\(_{3}\)) führt durch eine B-N-Kupplung über eine ClSiMe\(_{3}\)-Eliminierung zu unsymmetrischen (N-Aminoboryl)aminoboryl-Pt\(^{I}\)\(_{2}\)-Komplexen. Eine anschließende intramolekulare ClSiMe\(_{3}\)-Eliminierung des tBu-Derivats führt zu einer Cyclisierung der BNBN-Einheit unter Bildung eines einzigartigen 1,3,2,4-Diazadiboretidin-2-yl-Liganden. Im Gegensatz hierzu steht die analoge Reaktion mit Br\(_{2}\)BN(SiMe\(_{3}\))\(_{2}\), die über eine zweifache BrSiMe\(_{3}\)-Eliminierung zu einem Pt\(^{II}\)\(_{2}\)-A-Frame-Komplex führt, der von einem linearen Isoster des Butatriens verbrückt wird. Strukturelle und theoretische Daten bestätigen eine π-Elektronen-Delokalisierung über die gesamte BNBN-Einheit.
KW  - 1,3,2,4-Diazadiboretidin-2-yl-Ligand
KW  - A-Frame-Komplex
KW  - B-N-Kupplung
KW  - Butatrien-Analogon
KW  - Isosterie
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-244792
VL  - 133
IS  - 31
SP  - 17000
EP  - 17004
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  - Gerlach, Marius
A1  - Monninger, Sophie
A1  - Schleier, Domenik
A1  - Hemberger, Patrick
A1  - Goettel, James T.
A1  - Braunschweig, Holger
A1  - Fischer, Ingo
T1  - Photoelectron Photoion Coincidence Spectroscopy of NCl\(_{3}\) and NCl\(_{2}\)
JF  - ChemPhysChem
N2  - We investigate NCl\(_{3}\) and the NCl\(_{2}\) radical by photoelectron-photoion coincidence spectroscopy using synchrotron radiation. The mass selected threshold photoelectron spectrum (ms-TPES) of NCl\(_{3}\) is broad and unstructured due to the large geometry change. An ionization energy of 9.7±0.1 eV is estimated from the spectrum and supported by computations. NCl2 is generated by photolysis at 213 nm from NCl\(_{3}\) and its ms-TPES shows an extended vibrational progression with a 90 meV spacing that is assigned to the symmetric N−Cl stretching mode in the cation. An adiabatic ionization energy of 9.94 ± 0.02 eV is determined.
KW  - radicals
KW  - photoelectron spectroscopy
KW  - synchrotron radiation
KW  - nitrogen trichloride
KW  - photolysis
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-257322
VL  - 22
IS  - 21
ER  - 
TY  - INPR
A1  - Muessig, Jonas H.
A1  - Thaler, Melanie
A1  - Dewhurst, Rian D.
A1  - Paprocki, Valerie
A1  - Seufert, Jens
A1  - Mattock, James D.
A1  - Vargas, Alfredo
A1  - Braunschweig, Holger
T1  - Phosphine-Stabilized Diiododiborenes: Isolable Diborenes with Six Labile Bonds
T2  - Angewandte Chemie, International Edition
N2  - The lability of B=B, B-P and B-halide bonds is combined in the syntheses of the first diiododiborenes. In a series of reactivity tests, these diiododiborenes demonstrate cleavage of all six of their central bonds in different ways, leading to products of B=B hydrogenation and dihalogenation as well as halide exchange.
KW  - boron
KW  - low-valent main-group species
KW  - iodine
KW  - multiple bonding
KW  - 1,2-additions
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-178608
N1  - This is the pre-peer reviewed version of the following article: J. H. Muessig, M. Thaler, R. D. Dewhurst, V. Paprocki, J. Seufert, J. D. Mattock, A. Vargas, H. Braunschweig, Angew. Chem. Int. Ed. 2019, 58, 4405, which has been published in final form at https://doi.org/10.1002/anie.201814230. 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  -