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  - 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  - Stennett, Tom E.
A1  - Jayaraman, Arumugam
A1  - Brückner, Tobias
A1  - Schneider, Lea
A1  - Braunschweig, Holger
T1  - Hydrophosphination of boron–boron multiple bonds
JF  - Chemical Science
N2  - Five compounds containing boron–boron multiple bonds are shown to undergo hydrophosphination reactions with diphenylphosphine in the absence of a catalyst. With diborenes, the products obtained are highly dependent on the substitution pattern at the boron atoms, with both 1,1- and 1,2- hydrophosphinations observed. With a symmetrical diboryne, 1,2-hydrophosphination yields a hydro(phosphino)diborene. The different mechanistic pathways for the hydrophosphination of diborenes are rationalised with the aid of density functional theory calculations.
KW  - boron
KW  - diborenes
KW  - diborynes
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-240681
VL  - 11
ER  - 
TY  - INPR
A1  - Schmidt, Uwe
A1  - Fantuzzi, Felipe
A1  - Arrowsmith, Merle
A1  - Hermann, Alexander
A1  - Prieschl, Dominic
A1  - Rempel, Anna
A1  - Engels, Bernd
A1  - Braunschweig, Holger
T1  - Tuneable reduction of cymantrenylboranes to diborenes or borylene-derived boratafulvenes
T2  - Chemical Communications
N2  - Whereas the reduction of N-heterocyclic carbene (NHC)-stabilised cymantrenyldibromoboranes, (NHC)BBr\(_2\)Cym, in benzene results in formation of the corresponding diborenes (NHC)\(_2\)B\(_2\)Cym\(_2\), a change of solvent to THF yields a borylene of the form (NHC)\(_2\)BCym, stabilised through its boratafulvene resonance form.
KW  - Borylene
KW  - Diborene
KW  - Boranes
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-222149
ER  - 
TY  - JOUR
A1  - Liu, Siyuan
A1  - Légaré, Marc-André
A1  - Seufert, Jens
A1  - Prieschl, Dominic
A1  - Rempel, Anna
A1  - Englert, Lukas
A1  - Dellermann, Theresa
A1  - Paprocki, Valerie
A1  - Stoy, Andreas
A1  - Braunschweig, Holger
T1  - 2,2′-Bipyridyl as a Redox-Active Borylene Abstraction Agent
JF  - Inorganic Chemistry
N2  - 2,2′-Bipyridyl is shown to spontaneously abstract a borylene fragment (R–B:) from various hypovalent boron compounds. This process is a redox reaction in which the bipyridine is reduced and becomes a dianionic substituent bound to boron through its two nitrogen atoms. Various transition metal–borylene complexes and diboranes, as a well as a diborene, take part in this reaction. In the latter case, our results show an intriguing example of the homolytic cleavage of a B═B double bond.
KW  - Borylene
KW  - Heterocycles
KW  - Boron
KW  - Main-group chemistry
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-215595
N1  - This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Inorganic Chemistry, copyright © American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/acs.inorgchem.0c01383.
VL  - 59
IS  - 15
ER  - 
TY  - JOUR
A1  - 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  - 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  - 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  - 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  -