TY - JOUR A1 - Ramler, Jacqueline A1 - Poater, Jordi A1 - Hirsch, Florian A1 - Ritschel, Benedikt A1 - Fischer, Ingo A1 - Bickelhaupt, F. Matthias A1 - Lichtenberg, Crispin T1 - Carbon monoxide insertion at a heavy p-block element: unprecedented formation of a cationic bismuth carbamoyl JF - Chemical Science N2 - Major advances in the chemistry of 5th and 6th row heavy p-block element compounds have recently uncovered intriguing reactivity patterns towards small molecules such as H\(_2\), CO\(_2\), and ethylene. However, well-defined, homogeneous insertion reactions with carbon monoxide, one of the benchmark substrates in this field, have not been reported to date. We demonstrate here, that a cationic bismuth amide undergoes facile insertion of CO into the Bi–N bond under mild conditions. This approach grants direct access to the first cationic bismuth carbamoyl species. Its characterization by NMR, IR, and UV/vis spectroscopy, elemental analysis, single-crystal X-ray analysis, cyclic voltammetry, and DFT calculations revealed intriguing properties, such as a reversible electron transfer at the bismuth center and an absorption feature at 353 nm ascribed to a transition involving σ- and π-type orbitals of the bismuth-carbamoyl functionality. A combined experimental and theoretical approach provided insight into the mechanism of CO insertion. The substrate scope could be extended to isonitriles. KW - carbon monoxide KW - p-block element Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-181627 VL - 10 ER - TY - THES A1 - Rieger, Max T1 - Preconcentration with Metal-Organic Frameworks as adsorbents for airborne Explosives and Hazardous Materials - A study using inverse gas chromatography T1 - Anreicherung mit Metal-Organic Frameworks als „Adsorbentien für luftgetragene Explosiv- und Gefahrstoffe - Eine Studie mit inverser Gaschromatographie" N2 - Sensitivity and selectivity remain the central technical requirement for analytical devices, detectors and sensors. Especially in the gas phase, concentrations of threat substances can be very low (e.g. explosives) or have severe effects on health even at low concentrations (e.g. benzene) while it contains many potential interferents. Preconcentration, facilitated by active or passive sampling of air by an adsorbent, followed by thermal desorption, results in these substances being released in a smaller volume, effectively increasing their concentration. Traditionally, a wide range of adsorbents, such as active carbons or porous polymers, are used for preconcentration. However, many adsorbents either show chemical reactions due to active surfaces, serious water retention or high background emission due to thermal instability. Metal-organic frameworks (MOFs) are a hybrid substance class, composed inorganic and organic building blocks, being a special case of coordination polymers containing pores. They can be tailored for specific applications such as gas storage, separation, catalysis, sensors or drug delivery. This thesis is focused on investigating MOFs for their use in thermal preconcentration for airborne detection systems. A pre-screening method for MOF-adsorbate interactions was developed and applied, namely inverse gas chromatography (iGC). Using this pulse chromatographic method, the interaction of MOFs and molecules from the class of explosives and volatile organic compounds was studied at different temperatures and compared to thermal desorption results. In the first part, it is shown that archetype MOFs (HKUST-1, MIL-53 and Fe-BTC) outperformed the state-of-the-art polymeric adsorbent Tenax® TA in nitromethane preconcentration for a 1000 (later 1) ppm nitromethane source. For HKUST-1, a factor of more than 2000 per g of adsorbent was achieved, about 100 times higher than for Tenax. Thereby, a nitromethane concentration of 1 ppb could be increased to 2 ppm. High enrichment is addressed to the specific interaction of the nitro group as by iGC, which was determined by comparing nitromethane’s free enthalpy of adsorption with the respective saturated alkane. Also, HKUST-1 shows a similar mode of sorption (enthalpy-entropy compensation) for nitro and saturated alkanes. In the second part, benzene of 1 ppm of concentration was enriched with a similar setup, using 2nd generation MOFs, primarily UiO-66 and UiO-67, under dry and humid (50 %rH) conditions using constant sampling times. Not any MOF within the study did surpass the polymeric Tenax in benzene preconcentration. This is most certainly due to low sampling times – while Tenax may be highly saturated after 600 s, MOFs are not. For regular UiO-66, four differently synthesized samples showed a strongly varying behavior for dry and humid enrichment which cannot be completely explained. iGC investigations with regular alkanes and BTEX compounds revealed that confinement factors and dispersive surface energy were different for all UiO-66 samples. Using physicochemical parameters from iGC, no unified hypothesis explaining all variances could be developed. Altogether, it was shown that MOFs can replace or add to state-of-the-art adsorbents for the enrichment of specific analytes with preconcentration being a universal sensitivity-boosting concept for detectors and sensors. Especially with iGC as a powerful screening tool, most suitable MOFs for the respective target analyte can be evaluated. iGC can be used for determining “single point” retention volumes, which translate into partition coefficients for a specific MOF × analyte × temperature combination. N2 - Empfindlichkeit und Selektivität bleiben die zentralen technischen Anforderungen an analytische Geräte, Detektoren und Sensoren. Speziell in der Gasphase können die Konzentrationen von Gefahrstoffen sehr niedrig sein (z. B. Explosivstoffe) oder bereits bei niedrigen Konzentrationen schädigende Auswirkungen auf die Gesundheit aufweisen (z. B. Benzol) während sie viele potenzielle Interferenzien enthält. Präkonzentration, die durch aktives oder passives Sampling von Luft durch ein Adsorbens, gefolgt von einer Thermodesorption realisiert wird, setzt diese Substanzen effektiv in einem kleineren Volumen frei, was zu einer Erhöhung der Konzentration führt. Üblicherweise wird hierfür eine breite Auswahl an Adsorbentien wie Aktivkohlen oder poröse Polymere verwendet. Jedoch weisen viele Adsorbentien entweder chemische Reaktionen wegen aktiver Oberflächen, starke Wasserretention oder hohe Hintergrundemission wegen thermischer Instabilität auf. Metal-organic frameworks (MOFs) sind eine hybride Substanzklasse, ein Spezialfall der porösen Koordinationspolymere, die aus anorganischen und organischen Baugruppen aufgebaut sind. Sie können für spezifische Anwendungen wie Gasspeicherung, Trennung, Katalyse, Sensorik oder Wirkstofftransport maßgeschneidert werden. Diese Arbeit befasst sich hauptsächlich mit der Untersuchung von MOFs bei der thermischen Anreicherung für luftgetragene Detektionssysteme. Eine Methode zur schnellen Untersuchung von MOF-Analyt Interaktionen wurde entwickelt und angewendet, die inverse Gaschromatographie (iGC). Mit dieser pulschromatographischen Methode wurde die Interaktion von MOFs und Molekülen aus der Klasse der Explosivstoffe sowie Klasse der flüchtigen organischen Verbindungen (VOCs) in der Gasphase bei verschiedenen Temperaturen untersucht und mit Thermodesorptionsmessungen verglichen. Im ersten Teil der Arbeit würde gezeigt das Modell-MOFs (HKUST-1, MIL-53 und Fe-BTC) den polymeren Standard Tenax® TA beim Anreichern von Nitromethan an einer 1000 (später 1) ppm Nitromethan Quelle übertrafen. Im Fall von HKUST-1 konnte ein Faktor von 2000 pro Gramm erreicht werden, etwa 100-fach höher als für Tenax. Auf diese Weise könnte eine Nitromethan Konzentration von 1 ppb auf 2 ppm erhöht werden. Diese hohen Anreicherungsfaktoren entstammen vermutlich der hohen spezifischen Wechselwirkung der Nitrogruppe mit den MOFs. Diese wurden durch iGC beim Vergleich von Nitromethans freier Adsorptionsenthalpie mit dem entsprechenden gesättigten Alkan ermittelt. HKUST-1 weist auch einen ähnlichen Adsorptionsmodus (Enthalpie-Entropie Kompensation) für Nitro- und gesättigte Alkane auf. Im zweiten Teil der Arbeit wurde die Anreicherung von 1 ppm Benzol, mit einem ähnlichen Aufbau und anderen MOFs, hauptsächlich UiO-66 und UiO-67, unter trockenen und feuchten (50 %rF) Bedingungen bei konstanten Samplingzeiten, untersucht. Hierbei konnte kein MOF das polymere Tenax beim Anreichern von Benzol übertreffen. Dies liegt vermutlich an den niedrigen Samplingzeiten – während Tenax nach 600 s bereits stark gesättigt ist, gilt dies nicht für MOFs. Im Fall von UiO-66 zeigten vier Proben unterschiedlicher Herkunft ein stark unterschiedliches Verhalten bei trockener und feuchter Anreicherung welches nicht vollständig erklärt werden kann. iGC Untersuchungen mit gesättigten Alkanen und BTEX-Verbindungen konnten aufzeigen, dass räumliche Beschränktheitsfaktoren und dispersive Oberflächenenergien für alle vier Proben unterschiedlich waren. Mit physikochemischen Parametern aus iGC-Messungen konnte jedoch keine einheitliche Hypothese zum Unterscheiden der Proben entwickelt werden. Insgesamt konnte gezeigt werden, dass MOFs bestehende Adsorbens-Standards zum Anreichern von bestimmten Analyten ersetzen oder erweitern können, wobei Präkonzentration ein Konzept ist, welches universell die Empfindlichkeit eines Detektors oder Sensors steigern kann. Insbesondere mit iGC als mächtiges Werkzeug zur Vorselektion können passende MOFs für die entsprechenden Zielanalyten evaluiert werden. Ebenso kann iGC auch zur Bestimmung von Einzelpunkt Retentionsvolumen, welche Verteilungskoeffizienten für eine bestimmte MOF × Analyt × Temperatur Kombination entsprechen, genutzt werden. KW - Metallorganisches Netzwerk KW - MOF KW - Gas chromatography KW - iGC KW - Explosives KW - Preconcentration KW - Explosivstoff KW - Inverse Gaschromatographie Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-177750 ER - TY - JOUR A1 - Brückner, Tobias A1 - Dewhurst, Rian D. A1 - Dellermann, Theresa A1 - Müller, Marcel A1 - Braunschweig, Holger T1 - Mild synthesis of diboryldiborenes by diboration of B–B triple bonds JF - Chemical Science N2 - A set of diboryldiborenes are prepared by the mild, catalyst-free, room-temperature diboration of the B–B triple bonds of doubly base-stabilized diborynes. Two of the product diboryldiborenes are found to be air- and water-stable in the solid state, an effect that is attributed to their high crystallinity and extreme insolubility in a wide range of solvents. KW - boron KW - diborenes KW - diboration KW - triple bonds KW - diborynes Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-186306 VL - 10 ER - TY - INPR A1 - Légaré, Marc-André A1 - Pranckevicius, Conor A1 - Braunschweig, Holger T1 - Metallomimetic Chemistry of Boron T2 - Chemical Reviews N2 - The study of main-group molecules that behave and react similarly to transition-metal (TM) complexes has attracted significant interest in recent decades. Most notably, the attractive idea of replacing the all-too-often rare and costly metals from catalysis has motivated efforts to develop main-group-element-mediated reactions. Main-group elements, however, lack the electronic flexibility of TM complexes that arises from combinations of empty and filled d orbitals and that seem ideally suited to bind and activate many substrates. In this review, we look at boron, an element that despite its nonmetal nature, low atomic weight, and relative redox staticity has achieved great milestones in terms of TM-like reactivity. We show how in interelement cooperative systems, diboron molecules, and hypovalent complexes the fifth element can acquire a truly metallomimetic character. As we discuss, this character is powerfully demonstrated by the reactivity of boron-based molecules with H2, CO, alkynes, alkenes and even with N2. KW - boron KW - small-molecule activation KW - catalysis KW - low-valent main group chemistry Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-186317 N1 - This document is the unedited Author’sv ersion of a Submitted Work that was subsequently accepted for publication in Chemical Reviews,copyright ©American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/acs.chemrev.8b00561. ER - TY - INPR A1 - Brückner, Tobias A1 - Stennett, Tom E. A1 - Heß, Merlin A1 - Braunschweig, Holger T1 - Single and Double Hydroboration of B-B Triple Bonds and Conver- gent Routes to a Cationic Tetraborane T2 - Journal of the American Chemical Society N2 - A compound with a boron-boron triple bond is shown to undergo stepwise hydroboration reactions with catecholborane to yield an unsymmetrical hydro(boryl)diborene and a 2,3-dihydrotetraborane. Abstraction of H– from the latter compound produces an unusual cationic, planar tetraborane with a hydrogen atom bridging the central B2 moiety. Spectroscopic and crystallographic data and DFT calculations support a ‘protonated diborene’ structure for this compound, which can also be accessed via direct protonation of the corresponding diborene. KW - boron KW - multiple bonding KW - hydroboration Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-188632 N1 - This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Journal of the American Chemical Society, copyright © American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/jacs.9b07991. ER - TY - INPR A1 - Muessig, Jonas H. A1 - Thaler, Melanie A1 - Dewhurst, Rian D. A1 - Paprocki, Valerie A1 - Seufert, Jens A1 - Mattock, James D. A1 - Vargas, Alfredo A1 - Braunschweig, Holger T1 - Phosphine-Stabilized Diiododiborenes: Isolable Diborenes with Six Labile Bonds T2 - Angewandte Chemie, International Edition N2 - The lability of B=B, B-P and B-halide bonds is combined in the syntheses of the first diiododiborenes. In a series of reactivity tests, these diiododiborenes demonstrate cleavage of all six of their central bonds in different ways, leading to products of B=B hydrogenation and dihalogenation as well as halide exchange. KW - boron KW - low-valent main-group species KW - iodine KW - multiple bonding KW - 1,2-additions Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-178608 N1 - This is the pre-peer reviewed version of the following article: J. H. Muessig, M. Thaler, R. D. Dewhurst, V. Paprocki, J. Seufert, J. D. Mattock, A. Vargas, H. Braunschweig, Angew. Chem. Int. Ed. 2019, 58, 4405, which has been published in final form at https://doi.org/10.1002/anie.201814230. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. ER - TY - INPR A1 - Brückner, Tobias A1 - Arrowsmith, Merle A1 - Heß, Merlin A1 - Hammond, Kai A1 - Müller, Marcel A1 - Braunschweig, Holger T1 - Synthesis of fused B,N-heterocycles by alkyne cleavage, NHC ring-expansion and C-H activation at a diboryne T2 - Chemical Communications N2 - The addition of alkynes to a staturated N-heterocyclic carbene (NHC)-supported diboryne results in spontaneous cycloaddition, with complete B≡B and C≡C triple bond cleavage, NHC ring- expansion and activation of a variety of C-H bonds, leading to the formation of complex mixtures of fused B,N-heterocycles. KW - heterocycles KW - alkynes KW - boron KW - carbenes Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-184899 N1 - This is the pre-peer reviewed version of the following article: Chem. Commun., 2019,55, 6700-6703, which has been published in final form at doi:10.1039/C9CC02657F ER - TY - INPR A1 - Stennett, Tom E. A1 - Bissinger, Philipp A1 - Griesbeck, Stefanie A1 - Ullrich, Stefan A1 - Krummenacher, Ivo A1 - Auth, Michael A1 - Sperlich, Andreas A1 - Stolte, Matthias A1 - Radacki, Krzysztof A1 - Yao, Chang-Jiang A1 - Würthner, Frank A1 - Steffen, Andreas A1 - Marder, Todd B. A1 - Braunschweig, Holger T1 - Near-Infrared Quadrupolar Chromophores Combining Three-Coordinate Boron-Based Superdonor and Superacceptor Units T2 - Angewandte Chemie, International Edition N2 - In this work, two new quadrupolar A-π-D-π-A chromophores have been prepared featuring a strongly electron- donating diborene core and strongly electron-accepting dimesitylboryl F(BMes2) and bis(2,4,6-tris(trifluoromethyl)phenyl)boryl (BMes2) end groups. Analysis of the compounds by NMR spectroscopy, X-ray crystallography, cyclic voltammetry and UV-vis-NIR absorption and emission spectroscopy indicated that the compounds possess extended conjugated π-systems spanning their B4C8 cores. The combination of exceptionally potent π-donor (diborene) and π- acceptor (diarylboryl) groups, both based on trigonal boron, leads to very small HOMO-LUMO gaps, resulting in strong absorption in the near-IR region with maxima in THF at 840 and 1092 nm, respectively, and very high extinction coefficients of ca. 120,000 M-1cm-1. Both molecules also display weak near-IR fluorescence with small Stokes shifts. KW - boron KW - near-IR chromophores KW - conjugation KW - low-valent compounds KW - synthesis Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-180391 N1 - This is the pre-peer reviewed version of the following article: T. E. Stennett, P. Bissinger, S. Griesbeck, S. Ullrich, I. Krummenacher, M. Auth, A. Sperlich, M. Stolte, K. Radacki, C.-J. Yao, F. Wuerthner, A. Steffen, T. B. Marder, H. Braunschweig, Angew. Chem. Int. Ed. 2019, 58, 6449. , which has been published in final form at https://doi.org/10.1002/anie.201900889. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. ER - TY - INPR A1 - Arrowsmith, Merle A1 - Dömling, Michael A1 - Schmidt, Uwe A1 - Werner, Luis A1 - Castro, Abril C. A1 - Jiménez-Halla, J. Oscar C. A1 - Müssig, Jonas A1 - Prieschl, Dominic A1 - Braunschweig, Holger T1 - Spontaneous trans‐Selective Transfer Hydrogenation of Apolar B=B Double Bonds T2 - Angewandte Chemie, International Edition N2 - The transfer hydrogenation of NHC-supported diborenes with dimethylamine borane proceeds with high selectivity for the trans-1,2-dihydrodiboranes(6). DFT calculations suggest a stepwise proton-first-hydride-second reaction mechanism via an intermediate μ-hydrodiboronium dimethylaminoborate ion pair. KW - transfer hydrogenation KW - diborene KW - amine borane dehydrocoupling KW - diboranes KW - DFT mechanism Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-184874 N1 - This is the pre-peer reviewed version of the following article: M. Dömling, M. Arrowsmith, U. Schmidt, L. Werner, A. C. Castro, J. O. C. Jiménez-Halla, R. Bertermann, J. Müssig, D. Prieschl, H. Braunschweig, Angew. Chem. Int. Ed. 2019, 58, 9782. doi:10.1002/anie.201902656, which has been published in final form at https://doi.org/10.1002/anie.201902656. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. ER - TY - INPR A1 - Englert, Lukas A1 - Stoy, Andreas A1 - Arrowsmith, Merle A1 - Müssig, Jonas H. A1 - Thaler, Melanie A1 - Deißenberger, Andrea A1 - Häfner, Alena A1 - Böhnke, Julian A1 - Hupp, Florian A1 - Seufert, Jens A1 - Mies, Jan A1 - Damme, Alexander A1 - Dellermann, Theresa A1 - Hammond, Kai A1 - Kupfer, Thomas A1 - Radacki, Krzysztof A1 - Thiess, Torsten A1 - Braunschweig, Holger T1 - Stable Lewis Base Adducts of Tetrahalodiboranes: Synthetic Methods and Structural Diversity T2 - Chemistry - A European Journal N2 - A series of 22 new bis(phosphine), bis(carbene) and bis(isonitrile) tetrahalodiborane adducts has been synthesized, either by direct adduct formation with highly sensitive B2X4 precursors (X = Cl, Br, I) or by ligand exchange at stable B2X4(SMe2)2 precursors (X = Cl, Br) with labile dimethylsulfide ligands. The isolated compounds have been fully characterized using NMR spectroscopic, (C,H,N)- elemental and, for 20 of these compounds, X-ray crystallographic analysis, revealing an unexpected variation in the bonding motifs. Besides the classical B2X4L2 diborane(6) adducts, some of the more sterically demanding carbene ligands induce a halide displacement leading to the first halide-bridged monocationic diboron species, [B2X3L2]A (A = BCl4, Br, I). Furthermore, low-temperature 1:1 reactions of B2Cl4 with sterically demanding N-heterocyclic carbenes led to the formation of kinetically unstable mono-adducts, one of which was structurally characterized. A comparison of the NMR and structural data of new and literature-known bis-adducts shows several trends pertaining to the nature of the halides and the stereoelectronic properties of the Lewis bases employed. KW - diborane(6) KW - Lewis-base adducts KW - ligand exchange KW - crystallography KW - NMR spectroscopy Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-184888 N1 - This is the pre-peer reviewed version of the following article: L. Englert, A. Stoy, M. Arrowsmith, J. H. Muessig, M. Thaler, A. Deißenberger, A. Häfner, J. Böhnke, F. Hupp, J. Seufert, J. Mies, A. Damme, T. Dellermann, K. Hammond, T. Kupfer, K. Radacki, T. Thiess, H. Braunschweig, Chem. Eur. J. 2019, 25, 8612. https://doi.org/10.1002/chem.201901437, which has been published in final form at https://doi.org/10.1002/chem.201901437. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. ER -