@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{RamlerFantuzziGeistetal.2021, author = {Ramler, Jaqueline and Fantuzzi, Felipe and Geist, Felix and Hanft, Anna and Braunschweig, Holger and Engels, Bernd and Lichtenberg, Crispin}, title = {The dimethylbismuth cation: entry into dative Bi-Bi bonding and unconventional methyl exchange}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, doi = {10.1002/anie.202109545}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256543}, pages = {24388-24394}, year = {2021}, abstract = {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.}, language = {en} } @article{BergerRueheSchwarzmannetal.2021, author = {Berger, Sarina M. and R{\"u}he, Jessica and Schwarzmann, Johannes and Phillipps, Alexandra and Richard, Ann-Katrin and Ferger, Matthias and Krummenacher, Ivo and Tumir, Lidija-Marija and Ban, Željka and Crnolatac, Ivo and Majhen, Dragomira and Barišić, Ivan and Piantanida, Ivo and Schleier, Domenik and Griesbeck, Stefanie and Friedrich, Alexandra and Braunschweig, Holger and Marder, Todd B.}, title = {Bithiophene-Cored, mono-, bis-, and tris-(Trimethylammonium)-Substituted, bis-Triarylborane Chromophores: Effect of the Number and Position of Charges on Cell Imaging and DNA/RNA Sensing}, series = {Chemistry—A European Journal}, volume = {27}, journal = {Chemistry—A European Journal}, number = {56}, doi = {10.1002/chem.202102308}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256963}, pages = {14057-14072}, year = {2021}, abstract = {The synthesis, photophysical, and electrochemical properties of selectively mono-, bis- and tris-dimethylamino- and trimethylammonium-substituted bis-triarylborane bithiophene chromophores are presented along with the water solubility and singlet oxygen sensitizing efficiency of the cationic compounds Cat\(^{1+}\), Cat\(^{2+}\), Cat(i)\(^{2+}\), and Cat\(^{3+}\). Comparison with the mono-triarylboranes reveals the large influence of the bridging unit on the properties of the bis-triarylboranes, especially those of the cationic compounds. Based on these preliminary investigations, the interactions of Cat\(^{1+}\), Cat\(^{2+}\), Cat(i)\(^{2+}\), and Cat\(^{3+}\) with DNA, RNA, and DNApore were investigated in buffered solutions. The same compounds were investigated for their ability to enter and localize within organelles of human lung carcinoma (A549) and normal lung (WI38) cells showing that not only the number of charges but also their distribution over the chromophore influences interactions and staining properties.}, language = {en} } @article{HuangHuKrummenacheretal.2022, author = {Huang, Mingming and Hu, Jiefeng and Krummenacher, Ivo and Friedrich, Alexandra and Braunschweig, Holger and Westcott, Stephen A. and Radius, Udo and Marder, Todd B.}, title = {Base-Mediated Radical Borylation of Alkyl Sulfones}, series = {Chemistry—A European Journal}, volume = {28}, journal = {Chemistry—A European Journal}, number = {3}, doi = {10.1002/chem.202103866}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257281}, pages = {e202103866}, year = {2022}, abstract = {A practical and direct method was developed for the production of versatile alkyl boronate esters via transition metal-free borylation of primary and secondary alkyl sulfones. The key to the success of the strategy is the use of bis(neopentyl glycolato) diboron (B\(_{2}\)neop\(_{2}\)), with a stoichiometric amount of base as a promoter. The practicality and industrial potential of this protocol are highlighted by its wide functional group tolerance, the late-stage modification of complex compounds, no need for further transesterification, and operational simplicity. Radical clock, radical trap experiments, and EPR studies were conducted which show that the borylation process involves radical intermediates.}, language = {en} } @article{LindlGuoKrummenacheretal.2021, author = {Lindl, Felix and Guo, Xueying and Krummenacher, Ivo and Rauch, Florian and Rempel, Anna and Paprocki, Valerie and Dellermann, Theresa and Stennett, Tom E. and Lamprecht, Anna and Br{\"u}ckner, Tobias and Radacki, Krzysztof and B{\´e}langer-Chabot, Guillaume and Marder, Todd B. and Lin, Zhenyang and Braunschweig, Holger}, title = {Rethinking Borole Cycloaddition Reactivity}, series = {Chemistry—A European Journal}, volume = {27}, journal = {Chemistry—A European Journal}, number = {43}, doi = {10.1002/chem.202101290}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256888}, pages = {11226-11233}, year = {2021}, abstract = {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.}, language = {en} } @article{HessKrummenacherDellermannetal.2021, author = {Heß, Merlin and Krummenacher, Ivo and Dellermann, Theresa and Braunschweig, Holger}, title = {Rhodium-Mediated Stoichiometric Synthesis of Mono-, Bi-, and Bis-1,2-Azaborinines: 1-Rhoda-3,2-azaboroles as Reactive Precursors}, series = {Chemistry—A European Journal}, volume = {27}, journal = {Chemistry—A European Journal}, number = {37}, doi = {10.1002/chem.202100795}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256830}, pages = {9503-9507}, year = {2021}, abstract = {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.}, language = {en} } @article{GaertnerMarekArrowsmithetal.2021, author = {G{\"a}rtner, Annalena and Marek, Matth{\"a}us and Arrowsmith, Merle and Auerhammer, Dominic and Radacki, Krzysztof and Prieschl, Dominic and Dewhurst, Rian D. and Braunschweig, Holger}, title = {Boron- versus Nitrogen-Centered Nucleophilic Reactivity of (Cyano)hydroboryl Anions: Synthesis of Cyano(hydro)organoboranes and 2-Aza-1,4-diborabutatrienes}, series = {Chemistry—A European Journal}, volume = {27}, journal = {Chemistry—A European Journal}, number = {37}, doi = {10.1002/chem.202101025}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256853}, pages = {9694-9699}, year = {2021}, abstract = {Cyclic alkyl(amino)carbene-stabilized (cyano)hydroboryl anions were synthesized by deprotonation of (cyano)dihydroborane precursors. While they display boron-centered nucleophilic reactivity towards organohalides, generating fully unsymmetrically substituted cyano(hydro)organoboranes, they show cyano-nitrogen-centered nucleophilic reactivity towards haloboranes, resulting in the formation of hitherto unknown linear 2-aza-1,4-diborabutatrienes.}, 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{LuJayaramanFantuzzietal.2022, author = {Lu, Wei and Jayaraman, Arumugam and Fantuzzi, Felipe and Dewhurst, Rian D. and H{\"a}rterich, Marcel and Dietz, Maximilian and Hagspiel, Stephan and Krummenbacher, Ivo and Hammond, Kai and Cui, Jingjing and Braunschweig, Holger}, title = {An unsymmetrical, cyclic diborene based on a chelating CAAC ligand and its small-molecule activation and rearrangement chemistry}, series = {Angewandte Chemie International Edition}, volume = {61}, journal = {Angewandte Chemie International Edition}, number = {3}, doi = {10.1002/anie.202113947}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256576}, year = {2022}, abstract = {A one-pot synthesis of a CAAC-stabilized, unsymmetrical, cyclic diborene was achieved via consecutive two-electron reduction steps from an adduct of CAAC and B\(_2\)Br\(_4\)(SMe\(_2\))\(_2\). Theoretical studies revealed that this diborene has a considerably smaller HOMO-LUMO gap than those of reported NHC- and phosphine-supported diborenes. Complexation of the diborene with [AuCl(PCy\(_3\))] afforded two diborene-Au\(^I\) π complexes, while reaction with DurBH\(_2\), P\(_4\) and a terminal acetylene led to the cleavage of B-H, P-P, and C-C π bonds, respectively. Thermal rearrangement of the diborene gave an electron-rich cyclic alkylideneborane, which readily coordinated to Ag\(^I\) via its B=C double bond.}, language = {en} } @article{HaerterichMatlerDewhurstetal.2023, author = {H{\"a}rterich, Marcel and Matler, Alexander and Dewhurst, Rian D. and Sachs, Andreas and Oppel, Kai and Stoy, Andreas and Braunschweig, Holger}, title = {A step-for-step main-group replica of the Fischer carbene synthesis at a borylene carbonyl}, series = {Nature Communications}, volume = {14}, journal = {Nature Communications}, doi = {10.1038/s41467-023-36251-3}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-357270}, year = {2023}, abstract = {The Fischer carbene synthesis, involving the conversion of a transition metal (TM)-bound CO ligand to a carbene ligand of the form [=C(OR')R] (R, R' = organyl groups), is one of the seminal reactions in the history of organometallic chemistry. Carbonyl complexes of p-block elements, of the form [E(CO)n] (E = main-group fragment), are much less abundant than their TM cousins; this scarcity and the general instability of low-valent p-block species means that replicating the historical reactions of TM carbonyls is often very difficult. Here we present a step-for-step replica of the Fischer carbene synthesis at a borylene carbonyl involving nucleophilic attack at the carbonyl carbon followed by electrophilic quenching at the resultant acylate oxygen atom. These reactions provide borylene acylates and alkoxy-/silyloxy-substituted alkylideneboranes, main-group analogues of the archetypal transition metal acylate and Fischer carbene families, respectively. When either the incoming electrophile or the boron center has a modest steric profile, the electrophile instead attacks at the boron atom, leading to carbene-stabilized acylboranes - boron analogues of the well-known transition metal acyl complexes. These results constitute faithful main-group replicas of a number of historical organometallic processes and pave the way to further advances in the field of main-group metallomimetics.}, language = {en} } @article{SchmidtFantuzziKlopfetal.2021, author = {Schmidt, Paul and Fantuzzi, Felipe and Klopf, Jonas and Schr{\"o}der, Niklas B. and Dewhurst, Rian D. and Braunschweig, Holger and Engel, Volker and Engels, Bernd}, title = {Twisting versus delocalization in CAAC- and NHC-stabilized boron-based biradicals: the roles of sterics and electronics}, series = {Chemistry - A European Journal}, volume = {27}, journal = {Chemistry - A European Journal}, number = {16}, doi = {10.1002/chem.202004619}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256636}, pages = {5160-5170}, year = {2021}, abstract = {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.}, language = {en} } @article{DietzArrowsmithReichletal.2022, author = {Dietz, Maximilian and Arrowsmith, Merle and Reichl, Stephan and Lugo-Fuentes, Leonardo I. and Jim{\´e}nez-Halla, J. Oscar C. and Scheer, Manfred and Braunschweig, Holger}, title = {Stable Two-Legged Parent Piano-Stool and Mixed Diborabenzene-E\(_{4}\) (E=P, As) Sandwich Complexes of Group 8}, series = {Angewandte Chemie International Edition}, volume = {61}, journal = {Angewandte Chemie International Edition}, number = {36}, doi = {10.1002/anie.202206840}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-293880}, year = {2022}, abstract = {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.}, language = {en} } @article{MatlerArrowsmithSchorretal.2021, author = {Matler, Alexander and Arrowsmith, Merle and Schorr, Fabian and Hermann, Alexander and Hofmann, Alexander and Lenczyk, Carsten and Braunschweig, Holger}, title = {Reactivity of Terminal Iron Borylenes and Bis(borylenes) with Carbodiimides: Cycloaddition, Metathesis, Insertion and C-H Activation Pathways}, series = {European Journal of Inorganic Chemistry}, volume = {2021}, journal = {European Journal of Inorganic Chemistry}, number = {45}, doi = {10.1002/ejic.202100629}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257397}, pages = {4619-4631}, year = {2021}, abstract = {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.}, language = {en} } @article{RoyTroesterFantuzzietal.2021, author = {Roy, Dipak Kumar and Tr{\"o}ster, Tobias and Fantuzzi, Felipe and Dewhurst, Rian D. and Lenczyk, Carsten and Radacki, Krzysztof and Pranckevicius, Conor and Engels, Bernd and Braunschweig, Holger}, title = {Isolation and Reactivity of an Antiaromatic s-Block Metal Compound}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {7}, doi = {10.1002/anie.202014557}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224447}, pages = {3812 -- 3819}, year = {2021}, abstract = {The concepts of aromaticity and antiaromaticity have a long history, and countless demonstrations of these phenomena have been made with molecules based on elements from the p, d, and f blocks of the periodic table. In contrast, the limited oxidation-state flexibility of the s-block metals has long stood in the way of their participation in sophisticated π-bonding arrangements, and truly antiaromatic systems containing s-block metals are altogether absent or remain poorly defined. Using spectroscopic, structural, and computational techniques, we present herein the synthesis and authentication of a heterocyclic compound containing the alkaline earth metal beryllium that exhibits significant antiaromaticity, and detail its chemical reduction and Lewis-base-coordination chemistry.}, language = {en} } @article{KoleMerzAmaretal.2021, author = {Kole, Goutam Kumar and Merz, Julia and Amar, Anissa and Fontaine, Bruno and Boucekkine, Abdou and Nitsch, J{\"o}rn and Lorenzen, Sabine and Friedrich, Alexandra and Krummenacher, Ivo and Košćak, Marta and Braunschweig, Holger and Piantanida, Ivo and Halet, Jean-Fran{\c{c}}ois and M{\"u}ller-Buschbaum, Klaus and Marder, Todd B.}, title = {2- and 2,7-substituted para-N-methylpyridinium pyrenes: syntheses, molecular and electronic structures, photophysical, electrochemical, and spectroelectrochemical properties and binding to double-stranded (ds) DNA}, series = {Chemistry - A European Journal}, volume = {27}, journal = {Chemistry - A European Journal}, number = {8}, doi = {10.1002/chem.202004748}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256642}, pages = {2837-2853}, year = {2021}, abstract = {Two N-methylpyridinium compounds and analogous N-protonated salts of 2- and 2,7-substituted 4-pyridyl-pyrene compounds were synthesised and their crystal structures, photophysical properties both in solution and in the solid state, electrochemical and spectroelectrochemical properties were studied. Upon methylation or protonation, the emission maxima are significantly bathochromically shifted compared to the neutral compounds, although the absorption maxima remain almost unchanged. As a result, the cationic compounds show very large apparent Stokes shifts of up to 7200 cm\(^{-1}\). The N-methylpyridinium compounds have a single reduction at ca. -1.5 V vs. Fc/Fc\(^+\) in MeCN. While the reduction process was reversible for the 2,7-disubstituted compound, it was irreversible for the mono-substituted one. Experimental findings are complemented by DFT and TD-DFT calculations. Furthermore, the N-methylpyridinium compounds show strong interactions with calf thymus (ct)-DNA, presumably by intercalation, which paves the way for further applications of these multi-functional compounds as potential DNA-bioactive agents.}, 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{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} } @article{BruneckerArrowsmithFantuzzietal.2021, author = {Brunecker, Carina and Arrowsmith, Merle and Fantuzzi, Felipe and Braunschweig, Holger}, title = {Platin-vermittelte Kupplung von B=N-Einheiten: Synthese von BNBN-Analoga von 1,3-Dienen und Butatrien}, series = {Angewandte Chemie}, volume = {133}, journal = {Angewandte Chemie}, number = {31}, doi = {10.1002/ange.202106161}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-244792}, pages = {17000 -- 17004}, year = {2021}, abstract = {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\(_{3}\)) f{\"u}hrt durch eine B-N-Kupplung {\"u}ber eine ClSiMe\(_{3}\)-Eliminierung zu unsymmetrischen (N-Aminoboryl)aminoboryl-Pt\(^{I}\)\(_{2}\)-Komplexen. Eine anschließende intramolekulare ClSiMe\(_{3}\)-Eliminierung des tBu-Derivats f{\"u}hrt 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 {\"u}ber eine zweifache BrSiMe\(_{3}\)-Eliminierung zu einem Pt\(^{II}\)\(_{2}\)-A-Frame-Komplex f{\"u}hrt, der von einem linearen Isoster des Butatriens verbr{\"u}ckt wird. Strukturelle und theoretische Daten best{\"a}tigen eine π-Elektronen-Delokalisierung {\"u}ber die gesamte BNBN-Einheit.}, language = {de} }