@unpublished{BruecknerArrowsmithHessetal.2019, author = {Br{\"u}ckner, Tobias and Arrowsmith, Merle and Heß, Merlin and Hammond, Kai and M{\"u}ller, Marcel and Braunschweig, Holger}, title = {Synthesis of fused B,N-heterocycles by alkyne cleavage, NHC ring-expansion and C-H activation at a diboryne}, series = {Chemical Communications}, journal = {Chemical Communications}, doi = {10.1039/C9CC02657F}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-184899}, year = {2019}, abstract = {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of a variety of C-H bonds, leading to the formation of complex mixtures of fused B,N-heterocycles.}, language = {en} } @unpublished{StennettBissingerGriesbecketal.2019, author = {Stennett, Tom E. and Bissinger, Philipp and Griesbeck, Stefanie and Ullrich, Stefan and Krummenacher, Ivo and Auth, Michael and Sperlich, Andreas and Stolte, Matthias and Radacki, Krzysztof and Yao, Chang-Jiang and W{\"u}rthner, Frank and Steffen, Andreas and Marder, Todd B. and Braunschweig, Holger}, title = {Near-Infrared Quadrupolar Chromophores Combining Three-Coordinate Boron-Based Superdonor and Superacceptor Units}, series = {Angewandte Chemie, International Edition}, journal = {Angewandte Chemie, International Edition}, doi = {10.1002/anie.201900889}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-180391}, year = {2019}, abstract = {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 Both molecules also display weak near-IR fluorescence with small Stokes shifts.}, language = {en} } @unpublished{ArrowsmithDoemlingSchmidtetal.2019, author = {Arrowsmith, Merle and D{\"o}mling, Michael and Schmidt, Uwe and Werner, Luis and Castro, Abril C. and Jim{\´e}nez-Halla, J. Oscar C. and M{\"u}ssig, Jonas and Prieschl, Dominic and Braunschweig, Holger}, title = {Spontaneous trans-Selective Transfer Hydrogenation of Apolar B=B Double Bonds}, series = {Angewandte Chemie, International Edition}, journal = {Angewandte Chemie, International Edition}, doi = {10.1002/anie.201902656}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-184874}, year = {2019}, abstract = {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.}, language = {en} } @unpublished{EnglertStoyArrowsmithetal.2019, author = {Englert, Lukas and Stoy, Andreas and Arrowsmith, Merle and M{\"u}ssig, Jonas H. and Thaler, Melanie and Deißenberger, Andrea and H{\"a}fner, Alena and B{\"o}hnke, Julian and Hupp, Florian and Seufert, Jens and Mies, Jan and Damme, Alexander and Dellermann, Theresa and Hammond, Kai and Kupfer, Thomas and Radacki, Krzysztof and Thiess, Torsten and Braunschweig, Holger}, title = {Stable Lewis Base Adducts of Tetrahalodiboranes: Synthetic Methods and Structural Diversity}, series = {Chemistry - A European Journal}, journal = {Chemistry - A European Journal}, doi = {10.1002/chem.201901437}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-184888}, year = {2019}, abstract = {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.}, language = {en} } @article{HeRauchFriedrichetal.2019, author = {He, Jiang and Rauch, Florian and Friedrich, Alexandra and Sieh, Daniel and Ribbeck, Tatjana and Krummenacher, Ivo and Braunschweig, Holger and Finze, Maik and Marder, Todd B.}, title = {N-Heterocyclic Olefins as Electron Donors in Combination with Triarylborane Acceptors: Synthesis, Optical and Electronic Properties of D-π-A Compounds}, series = {Chemistry - A European Journal}, volume = {25}, journal = {Chemistry - A European Journal}, doi = {10.1002/chem.201903118}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204690}, pages = {13777-13784}, year = {2019}, abstract = {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.}, language = {en} } @article{ThiessMellerupBraunschweig2019, author = {Thiess, Torsten and Mellerup, Soren K. and Braunschweig, Holger}, title = {B-B Cleavage and Ring-Expansion of a 1,4,2,3-Diazadiborinine with N-Heterocyclic Carbenes}, series = {Chemistry - A European Journal}, volume = {25}, journal = {Chemistry - A European Journal}, number = {59}, doi = {10.1002/chem.201903259}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206173}, pages = {13572-13578}, year = {2019}, abstract = {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.}, language = {en} } @article{HattoriMichailSchmiedeletal.2019, author = {Hattori, Yohei and Michail, Evripidis and Schmiedel, Alexander and Moos, Michael and Holzapfel, Marco and Krummenacher, Ivo and Braunschweig, Holger and M{\"u}ller, Ulrich and Pflaum, Jens and Lambert, Christoph}, title = {Luminescent Mono-, Di-, and Tri-radicals: Bridging Polychlorinated Triarylmethyl Radicals by Triarylamines and Triarylboranes}, series = {Chemistry - A European Journal}, volume = {25}, journal = {Chemistry - A European Journal}, number = {68}, doi = {10.1002/chem.201903007}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-208162}, pages = {15463-15471}, year = {2019}, abstract = {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.}, language = {en} } @article{BelangerChabotBraunschweig2019, author = {B{\´e}langer-Chabot, Guillaume and Braunschweig, Holger}, title = {Hexahalogendiborat-Dianionen: Eine neue Klasse bin{\"a}rer Borhalogenide}, series = {Angewandte Chemie}, volume = {131}, journal = {Angewandte Chemie}, number = {40}, doi = {10.1002/ange.201906666}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212605}, pages = {14408-14412}, year = {2019}, abstract = {Die elektronenpr{\"a}zisen bin{\"a}ren Borsubhalogenide [B\(_2\)X\(_6\)]\(^{2-}\) (X=F, Br, I) wurden synthetisiert und strukturell im Festk{\"o}rper untersucht. Zudem konnte die vermutete Existenz von [B\(_2\)Cl\(_6\)]\(^{2-}\) mittels R{\"o}ntgendiffraktometrie nachgewiesen werden. Diese Dianionen sind isoelektronisch zu den Hexahalogeniden des Ethans und k{\"o}nnen als Homologe des Tetrahalogenborat-Anions BX\(_4\)\(^-\) betrachtet werden. Dar{\"u}ber hinaus geh{\"o}ren sie zu den seltenen Beispielen von elektronenpr{\"a}zisen bin{\"a}ren Borverbindungen (B\(_2\)X\(_4\), BX\(_3\), [BX\(_4\)]\(^-\)).}, language = {de} } @article{LenczykRoyOberdorfetal.2019, author = {Lenczyk, Carsten and Roy, Dipak Kumar and Oberdorf, Kai and Nitsch, J{\"o}rn and Dewhurst, Rian D. and Radacki, Krzysztof and Halet, Jean-Fran{\c{c}}ois and Marder, Todd B. and Bickelhaupt, Matthias and Braunschweig, Holger}, title = {Toward Transition-Metal-Templated Construction of Arylated B\(_{4}\) Chains by Dihydroborane Dehydrocoupling}, series = {Chemistry - A European Journal}, volume = {25}, journal = {Chemistry - A European Journal}, number = {72}, doi = {10.1002/chem.201904772}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-214324}, pages = {16544-16549}, year = {2019}, abstract = {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.}, language = {en} } @article{LenczykRoyNitschetal.2019, author = {Lenczyk, Carsten and Roy, Dipak Kumar and Nitsch, J{\"o}rn and Radacki, Krzysztof and Rauch, Florian and Dewhurst, Rian D. and Bickelhaupt, F. Matthias and Marder, Todd B. and Braunschweig, Holger}, title = {Steric Effects Dictate the Formation of Terminal Arylborylene Complexes of Ruthenium from Dihydroboranes}, series = {Chemistry - A European Journal}, volume = {25}, journal = {Chemistry - A European Journal}, number = {59}, issn = {1521-3765}, doi = {10.1002/chem.201902890}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219537}, pages = {13566-13571}, year = {2019}, abstract = {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.}, language = {en} } @article{Belanger‐ChabotBraunschweig2019, author = {B{\´e}langer-Chabot, Guillaume and Braunschweig, Holger}, title = {Hexahalodiborate Dianions: A New Family of Binary Boron Halides}, series = {Angewandte Chemie International Edition}, volume = {58}, journal = {Angewandte Chemie International Edition}, number = {40}, doi = {10.1002/anie.201906666}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219688}, pages = {14270-14274}, year = {2019}, abstract = {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\(_4\)]\(^-\).}, language = {en} } @unpublished{HermannArrowsmithTrujilloGonzalezetal.2020, author = {Hermann, Alexander and Arrowsmith, Merle and Trujillo-Gonzalez, Daniel and Jim{\´e}nez-Halla, J. Oscar C. and Vargas, Alfredo and Braunschweig, Holger}, title = {Trapping of a Borirane Intermediate in the Reductive Coupling of an Arylborane to a Diborene}, series = {Journal of the American Chemical Society}, journal = {Journal of the American Chemical Society}, doi = {10.1021/jacs.0c02306}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-203140}, year = {2020}, abstract = {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.}, language = {en} } @article{StennettJayaramanBrueckneretal.2020, author = {Stennett, Tom E. and Jayaraman, Arumugam and Br{\"u}ckner, Tobias and Schneider, Lea and Braunschweig, Holger}, title = {Hydrophosphination of boron-boron multiple bonds}, series = {Chemical Science}, volume = {11}, journal = {Chemical Science}, doi = {10.1039/c9sc05908c}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240681}, pages = {1335-1341}, year = {2020}, abstract = {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.}, language = {en} } @unpublished{SchmidtFantuzziArrowsmithetal.2020, author = {Schmidt, Uwe and Fantuzzi, Felipe and Arrowsmith, Merle and Hermann, Alexander and Prieschl, Dominic and Rempel, Anna and Engels, Bernd and Braunschweig, Holger}, title = {Tuneable reduction of cymantrenylboranes to diborenes or borylene-derived boratafulvenes}, series = {Chemical Communications}, journal = {Chemical Communications}, doi = {10.1039/D0CC06398C}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-222149}, year = {2020}, abstract = {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.}, language = {en} } @article{LiuLegareSeufertetal.2020, author = {Liu, Siyuan and L{\´e}gar{\´e}, Marc-Andr{\´e} and Seufert, Jens and Prieschl, Dominic and Rempel, Anna and Englert, Lukas and Dellermann, Theresa and Paprocki, Valerie and Stoy, Andreas and Braunschweig, Holger}, title = {2,2′-Bipyridyl as a Redox-Active Borylene Abstraction Agent}, series = {Inorganic Chemistry}, volume = {59}, journal = {Inorganic Chemistry}, number = {15}, doi = {10.1021/acs.inorgchem.0c01383}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-215595}, pages = {10866-10873}, year = {2020}, abstract = {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.}, language = {en} } @article{EwingDellermannAngelWongetal.2020, author = {Ewing, William C. and Dellermann, Theresa and Angel Wong, Y. T. and Mattock, James D. and Vargas, Alfredo and Bryce, David L. and Dewhurst, Rian D. and Braunschweig, Holger}, title = {\(\pi\)-Complexes of Diborynes with Main Group Atoms}, series = {Chemistry - An Asian Journal}, volume = {15}, journal = {Chemistry - An Asian Journal}, number = {10}, doi = {10.1002/asia.202000185}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-214677}, pages = {1553 -- 1557}, year = {2020}, abstract = {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.}, language = {en} } @article{ThiessErnstKupferetal.2020, author = {Thiess, Torsten and Ernst, Moritz and Kupfer, Thomas and Braunschweig, Holger}, title = {Facile Access to Substituted 1,4-Diaza-2,3-Diborinines}, series = {Chemistry - A European Journal}, volume = {26}, journal = {Chemistry - A European Journal}, number = {13}, doi = {10.1002/chem.201905356}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-214650}, pages = {2967 -- 2972}, year = {2020}, abstract = {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.}, language = {en} } @article{RauchFuchsFriedrichetal.2020, author = {Rauch, Florian and Fuchs, Sonja and Friedrich, Alexandra and Sieh, Daniel and Krummenacher, Ivo and Braunschweig, Holger and Finze, Maik and Marder, Todd B.}, title = {Highly Stable, Readily Reducible, Fluorescent, Trifluoromethylated 9-Borafluorenes}, series = {Chemistry - A European Journal}, volume = {26}, journal = {Chemistry - A European Journal}, number = {56}, doi = {10.1002/chem.201905559}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218390}, pages = {12794 -- 12808}, year = {2020}, abstract = {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.}, language = {en} } @article{HuangWangDewhurstetal.2020, author = {Huang, Zhenguo and Wang, Suning and Dewhurst, Rian D. and Ignat'ev, Nikolai V. and Finze, Maik and Braunschweig, Holger}, title = {Boron: Its Role in Energy-Related Processes and Applications}, series = {Angewandte Chemie International Edition}, volume = {59}, journal = {Angewandte Chemie International Edition}, number = {23}, doi = {10.1002/anie.201911108}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218514}, pages = {8800 -- 8816}, year = {2020}, abstract = {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.}, language = {en} } @article{GoettelGaoDotzaueretal.2020, author = {Goettel, James T. and Gao, Haopeng and Dotzauer, Simon and Braunschweig, Holger}, title = {\(^{Me}\)CAAC=N\(^{-}\): A Cyclic (Alkyl)(Amino)Carbene Imino Ligand}, series = {Chemistry - A European Journal}, volume = {26}, journal = {Chemistry - A European Journal}, number = {5}, doi = {10.1002/chem.201904715}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212662}, pages = {1136-1143}, year = {2020}, abstract = {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.}, language = {en} }