TY - JOUR A1 - Zhang, Xiaolei A1 - Friedrich, Alexandra A1 - Marder, Todd B. T1 - Copper-Catalyzed Borylation of Acyl Chlorides with an Alkoxy Diboron Reagent: A Facile Route to Acylboron Compounds JF - Chemistry—A European Journal N2 - Herein, the copper-catalyzed borylation of readily available acyl chlorides with bis(pinacolato)diboron, (B\(_{2}\)pin\(_{2}\)) or bis(neopentane glycolato)diboron (B\(_{2}\)neop\(_{2}\)) is reported, which provides stable potassium acyltrifluoroborates (KATs) in good yields from the acylboronate esters. A variety of functional groups are tolerated under the mild reaction conditions (room temperature) and substrates containing different carbon-skeletons, such as aryl, heteroaryl and primary, secondary, tertiary alkyl are applicable. Acyl N-methyliminodiacetic acid (MIDA) boronates can also been accessed by modification of the workup procedures. This process is scalable and also amenable to the late-stage conversion of carboxylic acid-containing drugs into their acylboron analogues, which have been challenging to prepare previously. A catalytic mechanism is proposed based on in situ monitoring of the reaction between p-toluoyl chloride and an NHC-copper(I) boryl complex as well as the isolation of an unusual lithium acylBpinOBpin compound as a key intermediate. KW - boronate KW - catalysis KW - borylation KW - carbonyl KW - copper Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318318 VL - 28 IS - 42 ER - TY - JOUR A1 - Zhang, Chonghe A1 - Liu, Xiaocui A1 - Wang, Junyi A1 - Ye, Qing T1 - A Three-Dimensional Inorganic Analogue of 9,10-Diazido-9,10-Diboraanthracene: A Lewis Superacidic Azido Borane with Reactivity and Stability JF - Angewandte Chemie N2 - Herein, we report the facile synthesis of a three-dimensional (3D) inorganic analogue of 9,10-diazido-9,10-dihydrodiboraantracene, which turned out to be a monomer in both the solid and solution state, and thermally stable up to 230 °C, representing a rare example of azido borane with boosted Lewis acidity and stability in one. Apart from the classical acid-base and Staudinger reactions, E−H bond activation (E=B, Si, Ge) was investigated. While the reaction with B−H (9-borabicyclo[3.3.1]nonane) led directly to the 1,1-addition on N\(_{α}\) upon N\(_{2}\) elimination, the Si−H (Et\(_{3}\)SiH, PhMe\(_{2}\)SiH) activation proceeded stepwise via 1,2-addition, with the key intermediates 5\(_{int}\) and 6\(_{int}\) being isolated and characterized. In contrast, the cooperative Ge−H was reversible and stayed at the 1,2-addition step. KW - E-H bond activation KW - boracycle KW - azido borane KW - lewis superacid KW - structure elucidation Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318322 VL - 61 IS - 36 ER - TY - JOUR A1 - Zapf, Ludwig A1 - Radius, Udo A1 - Finze, Maik T1 - 1,3-bis(tricyanoborane)imidazoline-2-ylidenate anion - a ditopic dianionic N-heterocyclic carbene ligand JF - Angewandte Chemie International Edition N2 - The 1,3-bis(tricyanoborane)imidazolate anion 1 was obtained in high yield from lithium imidazolate and B(CN)\(_3\)−pyridine adduct. Anion 1 is chemically very robust and thus allowed the isolation of the corresponding H\(_5\)O\(_2\)\(^+\) salt. Furthermore, monoanion 1 served as starting species for the novel dianionic N-heterocyclic carbene (NHC), 1,3-bis(tricyanoborane)imidazoline-2-ylidenate anion 3 that acts as ditopic ligand via the carbene center and the cyano groups at boron. First reactions of this new NHC 3 with methyl iodide, elemental selenium, and [Ni(CO)\(_4\)] led to the methylated imidazolate ion 4, the dianionic selenium adduct 5, and the dianionic nickel tricarbonyl complex 6. These NHC derivatives provide a first insight into the electronic and steric properties of the dianionic NHC 3. Especially the combination of properties, such as double negative charge, different coordination sites, large buried volume and good σ-donor and π-acceptor ability, make NHC 3 a unique and promising ligand and building block. KW - inorganic chemistry KW - N-heterocyclic carbene KW - anioniccarbene KW - boron KW - cyanoborate KW - imidazolate Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256498 VL - 60 IS - 33 ER - TY - JOUR A1 - Zapf, Ludwig A1 - Finze, Maik T1 - The crystal structure of poly[(μ \(_3\)-imidazolato-κ \(^3\) N:N:N′)(tetrahydrofuran- κ \(^1\) O)lithium(I)], C\(_7\)H\(_{11}\)LiN\(_2\)O JF - Zeitschrift für Kristallographie - New Crystal Structures N2 - C\(_7\)H\(_{11}\)LiN\(_2\)O, monoclinic, P2\(_1\)/c (no. 14), a = 8.9067(1) angstrom, b = 8.6975(1) angstrom, c = 10.2398(1) angstrom, beta = 101.900(3)degrees, V = 770.491(15) angstrom(3), Z = 4, R-gt (F) = 0.0338, wR(ref) (F\(^2\)) = 0.0925, T = 100 K. KW - acid sphingomyelinase KW - antidepressants KW - major depression KW - regulatory T cells KW - sphingolipids Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-260745 VL - 236 IS - 5 ER - TY - THES A1 - Zapf, Ludwig T1 - Novel Borane- and Phosphorane- Functionalized Anionic Carbene Ligands T1 - Neuartige Boran- und Phosphoran-funktionalisierte anionische Carbenliganden N2 - N-heterocyclic carbenes (NHC) are utilized for the stabilization of reactive compounds, for the activation of strong bonds, and as ligands in transition metal chemistry. In contrast to neutral NHCs, few examples of anionic or even dianionic NHCs are known. One approach for the synthesis of anionic carbenes is the deprotonation of neutral or anionic precursors, bearing Lewis acids instead of alkyl or aryl substituents. Following this strategy, novel anionic and dianionic NHCs, featuring weakly coordinating fluorinated borane and phosphorane substituents or coordinating tricyanoborane substituents were synthesized within the scope of this thesis. These carbenes possess unprecedented stabilities compared to related species. Furthermore, their electronic and steric properties can be directly adjusted by the type of Lewis acid attached. Their potential as ligands with highly shielding weakly coordinating substituents next to the carbene coordination center was demonstrated by the syntheses of the respective NHC selenium adducts and NHC gold(I) complexes. In contrast anionic NHCs with coordinating tricyanoborane moieties have an outstanding potential as ditopic ligands with coordination being possible at the carbene center and via the cyano groups. Their beneficial ligand properties were demonstrated by the syntheses of the respective NHC selenium adducts and NHC nickeltricarbonyl complexes. The combination of electronic properties, the large buried volume, the negative charge, the possibility to act as ditopic or ligands with weakly coordinating groups, and the ease of accessibility render borane- and phosphorane functionalized NHCs unique novel ligands. A further project of this PhD thesis deals with the steric properties of Lewis acids. Therefore, an easy-to-apply model was designed to quantify the steric demand of Lewis acids. Using the results of this evaluation, a second model was developed which judges the steric repulsion in Lewis acid/base adduct formation for arbitrary sets of acids and bases. N2 - N-heterozyklische Carbene (NHC) werden für die Stabilisierung reaktiver Verbindungen, für die Aktivierung starker Bindungen sowie als Liganden in der Übergangsmetallchemie eingesetzt. Im Gegensatz zu neutralen NHCs sind nur sehr wenige Vertreter anionischer oder gar dianionischer NHCs bekannt. Eine gute Strategie für deren Synthese stellt die Deprotonierung neutraler oder anionischer Vorstufen dar, welche Lewis-Säuren an Stelle von Alkyl- oder Arylsubstituenten tragen. Dieser Route folgend, wurden im Rahmen dieser Arbeit neue anionische und dianionische NHCs dargestellt, welche mit schwach koordinierenden, fluorierten Boran- und Phosphoransubstituenten oder mit koordinierenden Tricyanoboraneinheiten funktionalisiert sind. Diese Carbene besitzen beispiellose Stabilitäten, verglichen mit verwandten Verbindungen. Darüber hinaus können deren elektronischen und sterischen Eigenschaften direkt über die Wahl der Lewis-Säure gesteuert werden. Das Potential der Liganden mit stark abschirmenden schwach koordinierenden Substituenten in Nachbarschaft zum Carbenzentrum wurde durch die Synthese von NHC-Selen-Verbindungen sowie NHC-Gold(I)komplexen gezeigt. Im Gegensatz hierzu besitzen anionische NHCs mit koordinierenden Tricyanoboraneinheiten ein herausragendes Potential als ditope Liganden, da eine Koordination sowohl über das Carbenzentrum als auch über die Cyanogruppen möglich ist. Diese Vorteilhaften Ligandeneigenschaften wurden durch die Synthese entsprechender NHC-Selen-Addukte und NHC-Nickeltricarbonylkomplexe gezeigt. Somit macht die Kombination der elektronischen Eigenschaften, des großen verdeckten Volumens, der negativen Ladung, der Möglichkeit als ditoper Ligand oder als Ligand mit schwach koordinierenden Gruppen zu fungieren sowie die einfache Zugänglichkeit Boran- und Phosphoran-funktionalisierte NHCs zu einzigartigen neuartigen Liganden. Ein weiterer Teil dieser Arbeit setzt sich mit dem sterischen Anspruch von Lewis-Säuren auseinander. Hierfür wurde ein einfach anwendbares Modell entworfen, welches diesen quantifiziert. Ausgehend von diesen Ergebnissen wurde ein zweites Modell entwickelt, welches die sterische Abstoßung zwischen Lewis-Säure/Base-Addukten für beliebige Säure/Base-Kombinationen beurteilt. KW - Komplexe KW - Borane KW - Carbene KW - Phosphorane KW - Koordinationsverbindungen KW - Liganden Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-320781 ER - TY - THES A1 - Würtemberger-Pietsch, Sabrina T1 - Anionic and Neutral Lewis-Base Adducts of Diboron(4) Compounds T1 - Anionische und Neutrale Lewis-Basen Addukte von Diboran(4)-Verbindungen N2 - Anionic Adducts Sp2-sp3 tetraalkoxy diboron compounds have gained attention due to the development of new, synthetically useful catalytic reactions either with or without transition-metals. Lewis-base adducts of the diboron(4) compounds were suggested as possible intermediates in Cu catalyzed borylation reactions some time ago. However, intermolecular adducts of tetraalkoxy diboron compounds have not been studied yet in great detail. In preliminary studies, we have synthesized a series of anionic sp2-sp3 adducts of B2pin2 with alkoxy-groups (L = [OMe]–, [OtBu]–), a phenoxy-group (L = [4-tBuC6H4O]–) and fluoride (L = [F]–, with [nBu4N]+ as the counter ion) as Lewis-bases. Neutral Adducts Since their isolation and characterization, applications of N-heterocyclic carbenes (NHCs) and related molecules, e.g., cyclic alkylaminocarbenes (CAACs) and acyclic diaminocarbenes (aDCs), have grown rapidly. Their use as ligands in homogeneous catalysis and directly in organocatalysis, including recently developed borylation reactions, is now well established. Recently, several examples of ring expansion reactions (RER) involving NHCs were reported to take place at elevated temperatures, involving Be, B, and Si. Furthermore, preliminary studies in the group of Marder et al. showed the presence of neutral sp2-sp3 diboron compounds with B2pin2 and the NHC Cy2Im. In this work, we focused on the synthesis and characterization of further neutral sp2-sp3 as well as sp3-sp3 diboron adducts with B2cat2 and B2neop2 and different NHCs. Whereas the mono-NHC adduct is stable for several hours at temperatures up to 60 °C, the bis-NHC adducts undergo thermally induced rearrangement to form the ring expanded products compound 26 and 27. B2neop2 is much more reactive than B2cat2 giving ring expanded product 29 at room temperature in quantitative yields, demonstrating that NHC ring expansion and B–B bond cleavage can be very facile processes. Whereas the mono-NHC adduct is stable for several hours at temperatures up to 60 °C, the bis-NHC adducts undergo thermally induced rearrangement to form the ring expanded products compound 26 and 27. B2neop2 is much more reactive than B2cat2 giving ring expanded product 29 at room temperature in quantitative yields, demonstrating that NHC ring expansion and B–B bond cleavage can be very facile processes. N2 - Im Rahmen der vorliegenden Arbeit wurde die Synthese und das Reaktionsverhalten Lewis-Säuren/Lewis-Basen-Addukte von Diboran(4)-Verbindungen als Lewis-Säuren untersucht. Als Lewis-Basen dienten zum einem das Fluorid-Ion, zum anderen N-Heterozyklische Carbene. Ein Ziel der vorliegenden Arbeit war somit die Synthese und Charakterisierung anionischer sp2-sp3-Diboran-Verbindungen des Typs [B2(OR)4F][NMe4] (OR2 = Pinakol, Catechol und Neopentyl), die auf ihre Eigenschaft als „Boryl-Übertragungsreagenz“ gegenüber Diazoniumsalzen überprüft wurden. Der zweite Teil der Arbeit untersucht die Reaktion von Diboranen (B2cat2 und B2neop2) mit gesättigten und ungesättigten N-Heterozyklischen Carbenen (NHCs). Die neutralen, einfach- und zweifach-substituierten NHC-Addukte des Typs B2(OR)4•NHC und B2(OR)4•(NHC)2 wurden anschließend auf ihre thermische Stabilität untersucht. Die Ergebnisse dieser Arbeit zeigen zum einem, dass anionische Addukte des Typs [B2(OR)4F][NMe4] 4, 7 und 9 als „Boryl-Übertragungsreagenzien“ eingesetzt werden können. Ferner lassen sich ausgehend von Diboran(4)-Verbindungen durch die Umsetzung mit N Heterozyklischen Carbenen die einfach- und zweifach-substituierten NHC-Addukte B2(OR)4•NHC und B2(OR)4•(NHC)2 synthetisieren. Diese sind zum Teil instabil gegenüber einer Ringerweiterungsreaktion unter Insertion einer Boryleinheit in die C–N-Bindung des Carbens. Untersuchungen an NHC-Addukten von Boranen BR3 und HB(OR)2 zeigen weiterhin, dass die Addukte Ph3B•NHC gegenüber solchen Ringerweiterungen stabil sind. Die Addukte HB(OR)2•NHC sind je nach eingesetztem Carben und Boran entweder stabil oder reagieren unter B–H-Bindungsaktivierung zur Ringerweiterung des Carbens. KW - Addukt KW - Diborane KW - carben KW - Lewis-Base Adducts KW - Diboron(4) Compounds KW - Ring Expansion Reaction Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-136321 ER - TY - JOUR A1 - Wu, Zhu A1 - Roldao, Juan Carlos A1 - Rauch, Florian A1 - Friedrich, Alexandra A1 - Ferger, Matthias A1 - Würthner, Frank A1 - Gierschner, Johannes A1 - Marder, Todd B. T1 - Pure Boric Acid Does Not Show Room-Temperature Phosphorescence (RTP) JF - Angewandte Chemie N2 - Boric acid (BA) has been used as a transparent glass matrix for optical materials for over 100 years. However, recently, apparent room-temperature phosphorescence (RTP) from BA (crystalline and powder states) was reported (Zheng et al., Angew. Chem. Int. Ed. 2021, 60, 9500) when irradiated at 280 nm under ambient conditions. We suspected that RTP from their BA sample was induced by an unidentified impurity. Our experimental results show that pure BA synthesized from B(OMe)\(_{3}\) does not luminesce in the solid state when irradiated at 250–400 nm, while commercial BA indeed (faintly) luminesces. Our theoretical calculations show that neither individual BA molecules nor aggregates would absorb light at >175 nm, and we observe no absorption of solid pure BA experimentally at >200 nm. Therefore, it is not possible for pure BA to be excited at >250 nm even in the solid state. Thus, pure BA does not display RTP, whereas trace impurities can induce RTP. KW - boric acid KW - room-temperature phosphorescence (RTP) KW - optical materials Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318308 VL - 61 IS - 15 ER - TY - JOUR A1 - Wu, Zhu A1 - Nitsch, Jörn A1 - Marder, Todd B. T1 - Persistent room-temperature phosphorence from purely organic molecules and multi-component systems JF - Advanced Optical Materials N2 - Recently, luminophores showing efficient room-temperature phosphorescence (RTP) have gained tremendous interest due to their numerous applications. However, most phosphors are derived from transition metal complexes because of their intrinsic fast intersystem crossing (ISC) induced by strong spin–orbit coupling (SOC) constants of the heavy metal. Metal-free RTP materials are rare and have become a promising field because they are inexpensive and environmentally friendly. This review summarizes organic molecular materials with long triplet lifetimes at room temperature from the perspective of whether they stem from a molecular or multi-component system. Among purely organic phosphors, heteroatoms are usually introduced into the backbone in order to boost the singlet–triplet ISC rate constant. In multi-component systems, useful strategies such as host–guest, polymer matrix, copolymerization, and supramolecular assembly provide a rigid matrix to restrict nonradiative pathways thus realizing ultralong RTP. KW - inorganic chemistry KW - non-radiative decay KW - polymer matrix KW - intersystem crossing KW - luminescence KW - photophysics Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256415 VL - 9 IS - 20 ER - TY - JOUR A1 - Wu, Zhu A1 - Dinkelbach, Fabian A1 - Kerner, Florian A1 - Friedrich, Alexandra A1 - Ji, Lei A1 - Stepanenko, Vladimir A1 - Würthner, Frank A1 - Marian, Christel M. A1 - Marder, Todd B. T1 - Aggregation-Induced Dual Phosphorescence from (o-Bromophenyl)-Bis(2,6-Dimethylphenyl)Borane at Room Temperature JF - Chemistry—A European Journal N2 - Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non-radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers (o, m, p-bromophenyl)-bis(2,6-dimethylphenyl)boranes. Among the 3 isomers (o-, m- and p-BrTAB) synthesized, the ortho-one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. Based on theoretical calculations and crystal structure analysis of o-BrTAB, the short lifetime component is ascribed to the T\(^M_1\) state of the monomer which emits the higher energy phosphorescence. The long-lived, lower energy phosphorescence emission is attributed to the T\(^A_1\) state of an aggregate, with multiple intermolecular interactions existing in crystalline o-BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently. KW - AIE KW - luminescence KW - phosphorescence KW - triarylborane KW - triplet Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318297 VL - 28 IS - 30 ER - TY - THES A1 - Wu, Zhu T1 - Room Temperature Phosphorescence (RTP): Experimental And Theoretical Studies on Boron-Containing Materials T1 - Raumtemperaturphosphoreszenz (RTP): Experimentelle und theoretische Studien zu borhaltigen Materialien N2 - Persistent room temperature phosphorescent (RTP) luminophores have gained remarkable interest recently for a number of applications in security printing, OLEDs, optical storage, time-gated biological imaging and oxygen sensors. We report the first persistent RTP with lifetimes up to 0.5 s from simple triarylboranes which have no lone pairs. We also have prepared 3 isomeric (o, m, p-bromophenyl)-bis(2,6-dimethylphenyl)boranes. Among the 3 isomers (o-, m- and p-BrTAB) synthesized, the ortho-one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. At last, we checked the RTP properties from the boric acid. We found that the pure boric acid does not show RTP in the solid state. N2 - In letzter Zeit haben Luminophore, die eine effiziente Raumtemperatur-Phosphoreszenz (RTP) zeigen, aufgrund ihrer zahlreichen Anwendungen enormes Interesse gefunden. Die meisten phosphoreszierenden Materialien leiten sich jedoch von Übergangsmetallkomplexen ab, da ihr intrinsisches schnelles Intersystem Crossing (ISC) durch die starke Spin Bahn Kopplung (SOC) des Schwermetalls induziert wird. Metallfreie RTP Materialien sind selten und haben sich zu einem vielversprechenden Gebiet entwickelt, da sie kostengünstig und umweltfreundlich sind. Dieses Kapitel fasst organische molekulare Materialien mit langen Triplett Lebensdauern bei Raumtemperatur aus der Perspektive zusammen, ob sie aus einem molekularen oder Mehrkomponentensystem stammen. Bei rein organischen phosphoreszierenden Materialien werden üblicherweise Heteroatome in das Rückgrat eingeführt, um die Singulett Triplett ISC Geschwindigkeitskonstante zu erhöhen. In Mehrkomponentensystemen wird durch nützliche Strategien wie Wirt-Gast, Polymermatrix, Copolymerisation und supramolekulare Anordnung eine starre Matrixanordnung erreicht, durch die nichtstrahlende Pfade eingeschränkt und so ultralange RTP realisiert wird. ... KW - room temperature phosphorescence Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-260844 ER -