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- ItemSynthesis, Electronic Properties and Reactivity of [B12X11(NO2)]2− (X=F–I) Dianions(Weinheim : Wiley-VCH, 2020) Asmis, Knut R.; Beele, Björn B.; Jenne, Carsten; Kawa, Sebastian; Knorke, Harald; Nierstenhöfer, Marc C.; Wang, Xue-Bin; Warneke, Jonas; Warneke, Ziyan; Yuan, QinqinNitro-functionalized undecahalogenated closo-dodecaborates [B12X11(NO2)]2− were synthesized in high purities and characterized by NMR, IR, and Raman spectroscopy, single crystal X-diffraction, mass spectrometry, and gas-phase ion vibrational spectroscopy. The NO2 substituent leads to an enhanced electronic and electrochemical stability compared to the parent perhalogenated [B12X12]2− (X=F–I) dianions evidenced by photoelectron spectroscopy, cyclic voltammetry, and quantum-chemical calculations. The stabilizing effect decreases from X=F to X=I. Thermogravimetric measurements of the salts indicate the loss of the nitric oxide radical (NO.). The homolytic NO. elimination from the dianion under very soft collisional excitation in gas-phase ion experiments results in the formation of the radical [B12X11O]2−.. Theoretical investigations suggest that the loss of NO. proceeds via the rearrangement product [B12X11(ONO)]2−. The O-bonded nitrosooxy structure is thermodynamically more stable than the N-bonded nitro structure and its formation by radical recombination of [B12X11O]2−. and NO. is demonstrated. © 2020 The Authors. Published by Wiley-VCH GmbH
- ItemHeterogeneously Catalysed Oxidative Dehydrogenation of Menthol in a Fixed-Bed Reactor in the Gas Phase(Weinheim : Wiley-VCH-Verl., 2019) Kulik, Anna; Neubauer, Katja; Eckelt, Reinhard; Bartling, Stephan; Panten, Johannes; Köckritz, AngelaFor the first time, the oxidative dehydrogenation of (−)-menthol to (−)-menthone and (+)-isomenthone in a marketable quality was carried out in a continuous gas phase reactor as a sustainable process using molecular oxygen as green oxidant and solid catalysts which do not contaminate the product mixture and which are easily to remove. The diastereomeric purity remained largely unchanged. Three types of catalysts were found to be very active and selective in the formation of menthone and isomenthone: AgSr/SiO2, CuO distributed on a basic support and RuMnCe/CeO2, where Ru, Mn and Ce exist in an oxidized state. The best overall yield of menthon/isomenthone obtained with an Ag-based catalyst was 58 % at 64 % selectivity, with a Cu-based catalyst 41 % at 51 % selectivity and with a Ru-based catalyst 68 % at 73 % selectivity. Reaction conditions were widely optimized. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.