03 Fakultät Chemie
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Item Open Access An anionic mesoionic carbene (anMIC) and its transformation to metallo MIC‐boranes : synthesis and properties(2025) Rudolf, Richard; Todorovski, Andrej; Lederer, Vera; Neuman, Nicolás I.; Schubert, Hartmut; Sarkar, BiprajitNeutral mesoionic carbenes (MICs) based on a 1,2,3‐triazole core have had a strong impact on various branches of chemistry such as homogeneous catalysis, electrocatalysis, and photochemistry/photophysics. We present here the first general synthesis of anionic mesoionic carbenes (anMICs, 2) based on a 1,2,3‐triazole core and a borate backbone. The free anMIC is stable in solution under an inert atmosphere at low temperatures, and can be stored for several weeks. Analysis of donor properties shows that these anMICs are extremely strong σ‐donors, bypassing the donor properties of strong donors such as MICs, NHCs, anionic NHCs and N‐heterocyclic olefins. The room temperature conversion of the free anMICs leads to three equally interesting compound classes: an amide‐coordinated borane based on a MIC‐borane backbone (2BR3), a polymeric triazolide (1Li) and an amide‐coordinated metallo‐MIC‐borane. The metallo‐MIC‐borane (3Li) is an interesting precursor for the synthesis of further amide‐coordinated MIC‐borane compounds. Quantum chemical calculations have been used to elucidate the mechanism of transformation of the anMICs. We thus introduce three new categories of mesoionic compounds here with potential for different branches of chemistry and beyond.Item Open Access Synthese, Charakterisierung und röntgenographische Strukturbestimmung von Seltenerdmetall(III)-Fluoridchalkogeniden sowie NaY[SO4]2 und dessen Hydrat(2024) Buyer, Constantin; Schleid, Thomas (Prof. Dr.)Diese Arbeit beschäftigt sich mit der Synthese, Charakterisierung und röntgenographische Strukturbestimmung von Seltenerdmetall(III)-Fluoridchalkogeniden. Dies umfasst die Bastnäsite von La bis Nd, sowie Sm und Eu, welche hydrothermal synthetisiert wurden und deren Kristallstruktur mit Hilfe von Rietveld aus PXRD-Daten verfeinert wurden. Außerdem wurden die Trimorphe von LaFO untersucht, welche durch thermische Zersetzung von LaF[CO3] entstehen. Des Weiteren umfasst diese Arbeit den Polymorphismus von LaFSe. Auch weitere Verbindungen wie Sm7F12Cl2, Yb12,8F31 und Intergrowth-Phasen von CaF2 in SEFS, die sich den Seltenerdmetall(III)-Fluoridchalkogeniden zuordnen lassen, wurden synthetisiert und untersucht. Schließlich wurden noch NaY[SO4]2 und dessen Hydrat ausführlich untersucht.Item Open Access Temperature-resolved crystal structure of ethylene carbonate(2025) Westphal, Lea; Kochetov, Vladislav; Baran, Volodymyr; Hölderle, Tobias; Avdeev, Maxim; Diadkin, Vadim; Marshall, Kenneth; Schökel, Alexander; Opri, Klaudia; Niewa, Rainer; Porcher, Florence; Müller-Buschbaum, Peter; Senyshyn, AnatoliyEthylene carbonate (EC) is an organic solvent of the class of carbonate esters, which is used in state-of-the-art Li-ion batteries as part of the electrolyte mixture, being primarily responsible for the formation of a solid electrolyte interface. Thermal analysis showed that the sample’s melting point is 309 K. The crystal structure of EC is investigated using powder diffraction in a temperature range from 3 K up to its melting point, using neutron- and synchrotron-based radiation. Over the whole temperature range, the sample shows single-phase behavior with the space group being C 2/ c (No. 15), and given the detailed temperature dependence of the structural evolution, thermodynamic and mechanical properties of solid EC are studied. The local structure in both solid and liquid states was additionally investigated by total scattering diffraction and analysis of the pair distribution function. The results obtained are discussed in line with those of molecular dynamics simulations.Item Open Access The first members of the monoclinic lanthanoid(III) fluoride oxoarsenate(III) series Ln2F2[As2O5] (Ln=La - Nd and Sm)(2025) Locke, Ralf J. C.; Zimmer, Frank C.; Schleid, ThomasIn synthesis experiments for the preparation of Ln5F3[AsO3]4 representatives in evacuated glassy silica ampoules at temperatures of maximum 825 °C, surprisingly compounds with the composition Ln2F2[As2O5] could be obtained and subsequently also reproduced on target. The new Ln2F2[As2O5] representatives with Ln = La - Nd and Sm crystallize needle‐shaped in the monoclinic space group P21/c with lattice parameters ranging from a = 793.24(5) pm, b = 1346.39(9) pm, c = 1359.41(9) pm and β = 106.932(3)° for La2F2[As2O5] to a = 769.11(5) pm, b = 1307.50(9) pm, c = 1328.74(9) pm and β = 106.819(3)° for Sm2F2[As2O5] with Z = 8. Their crystal structure can be broken down into two parts consisting of infinite [Ln2F2]4+ and discrete [As2O5]4− units. Three distinct kinds of fluoride anions are trigonally planar surrounded by lanthanoid cations and another one carries even a fourth of them in their coordination sphere with a secondary contact resulting in a distorted tetrahedron. These [FLn3]8+ and [FLn3+1]11+ building blocks share common corners and edges creating strands {[F2Ln2]4+}, which propagate along [100]. The four different As3+ lone‐pair cations form ψ1‐tetrahedra [AsO3]3− with three oxygen atoms and are conversurally linked pairwisely creating dinuclear pyroanionic [As2O5]4− units. These [As2O5]4− groups arrange themselves alternatingly along [100] with their lone pairs pointing into central empty channels. The {[F2Ln2]4+} strands are linked to the [As2O5]4− units via four distinguishable Ln3+ cations providing them coordination numbers of eight and nine. Raman spectroscopy confirmed that no (OH)− groups resulting from the synthesis were present apt to replace part of the F− and the stoichiometry Ln2F2[As2O5] was verified using WDXS elemental analyses.Item Open Access Activation and fixation of atmospheric CO2 through a 1,2,3‐triazole‐based mesoionic carbene-borane adduct(2025) Neubrand, Maren; Stubbe, Jessica; Rudolf, Richard; Walter, Robert R. M.; Nößler, Maite; Sarkar, BiprajitCapturing atmospheric CO2 and converting it to valuable chemicals are important goals in contemporary science. We present here a simple, transition metal‐free triazolylidene–borane adduct that can capture atmospheric CO2 and convert it to formate. Several key intermediates were isolated and characterized by a combination of multinuclear NMR spectroscopy, IR spectroscopy and single crystal X‐ray diffraction. A first closed cycle for the conversion of CO2 to formic acid by using the aforementioned triazolylidene–borane compound is presented as well.Item Open Access Alkaline earth metal nitride chalcogenides, Ca6N2Se3, Sr6N2Se3 and Sr6N2Te3(2025) Sun, Guowei; Niewa, RainerThe novel isotypic hexagonal alkaline earth metal nitride chalcogenides Ca6N2Se3, Sr6N2Se3 and Sr6N2Te3 (Rmathematical equation (No.167); Z=6) were synthesized from Ca(Sr)/Na flux at 1173 K. The compounds belong to the rare class of ternary metal nitride chalcogenides. The structures feature the shortest Ca/Sr-N bonds within the regular trigonal antiprismatic coordination (Ca-N: 235.17(8); Sr-N: 251.20(6) pm). Two crystallographic distinct nitrogen atoms are coordinated in a trigonal antiprism and a twisted trigonal prism, respectively, and are alternatively condensed via trigonal trans-faces to form one-dimensional chains mathematical equation . The chalcogenide ions in comparison realize rather ambiguous environments. Raman spectroscopic data are reportedItem Open Access N-heterozyklische Phospheniumionen : eine noble Ergänzung zu einem unedlen Metall(2024) Birchall, Nicholas; Gudat, Dietrich (Prof. Dr. Dr h.c.)Die vorliegende Arbeit befasst sich mit Untersuchungen zur Aktivierung und Funktionalisierung kleiner Moleküle (H2, CO2, CO, Alkene, Alkine) an Komplexen mit einem unedlen Metallzentrum. Hierbei kommen neue Formen der Metall-Ligand-Kooperativität (engl. MLC) zum Einsatz, die eine Nutzbarkeit dieser (unedlen) Metallkomplexe in einer Vielzahl an katalytischen Transformationen ermöglichen.Item Open Access Filling voids : cubic carbodiimide nitride nitridometalates (Ba6Nx)2[MN4][CN2]6 of M = Zr, Hf, Nb, Ta, Mo, and W(2026) Höhn, Peter; Link, Lukas; Reckeweg, Olaf; Prots, Yurii; Niewa, RainerCubic carbodiimide nitride nitridometalates (Ba6Nx)2[MN4][CN2]6 of M = Zr, Hf, Nb, Ta, Mo, and W are synthesized by various high-temperature reactions and their respective crystal structures were investigated using X-ray diffraction. Red transparent crystals (Ba6N5/6)2[NbVN4][CN2]6 in space group Im3 as aristotype exhibit site disorder of the [NbN4]7 anion and an about 42% occupation of a further nitride ion site for charge balance. Upon reduced nitrogen content on the latter site, dark gray (Ba6Nx)2[NbN4][CN2]6 with x=0.55(7) crystallizes in the direct subgroup I23 with fully ordered tetrahedra. This structure is also observed for crystals of red (Ba6N2/3)2[HfIVN4][CN2]6 with ordered tetrahedra [HfN4]8. Dark red (Ba6N)2[WVIN4][CN2]6 with enlarged nitride content balancing the higher charge of the transition metal in oxidation state þ6 crystallizes in the different direct subgroup Pn3, and shows an unlike site order for the nitride ions. Depending on the (dis)order of the nitride ions, the nitridometalate ions (dis)order in different patterns. Powder diffraction data of microcrystalline samples indicate identical structures of the zirconium and hafnium compounds in I23, but realization of space group Pn3 of the red compounds of not only molybdenum and tungsten but also niobium and tantalum. The IR spectra corroborate the identity of the carbodiimide anion.Item Open Access On the rubidium thiotellurate(IV) Rb2[TeS3] and its tritohydrate Rb2[TeS3] ⋅ 1/3 H2O(2024) Wolff, Klaus K.; Pfitzner, Arno; Schleid, ThomasRb2[TeS3] and Rb2[TeS3] ⋅ 1/3 H2O were obtained from rubidium azide (RbN3), tellurium and sulfur in 2 : 1 : 3 molar ratios from evacuated fused silica ampoules at 500 °C under more or less anhydrous conditions. Both compounds crystallize orthorhombically in the space group P212121 (Rb2[TeS3]: a=873.42(6) pm, b=1316.73(9) pm, c=2064.59(14) pm; Rb2[TeS3] ⋅ 1/3 H2O: a=872.97(6) pm, b=1299.82(9) pm, c=2148.26(15) pm, both at -173 °C for Z =12) and contain discrete ψ1‐tetrahedral [TeS3]2- anions (d(Te-S)=232-236 pm) in layerwise arrangements. The difference results from the water of hydration in Rb2[TeS3] ⋅ 1/3 H2O, which increases the coordination numbers of half of the six crystallographically distinct Rb+ cations from six and seven (only sulfur) to seven and almost eight by providing with oxygen from H2O an extra ligand (d(Rb-O)=290-318 pm). Red Rb2[TeS3] transforms pseudo‐topotactically into yellow Rb2[TeS3] ⋅ 1/3 H2O immediately upon contact with moist atmosphere. The compounds were screened with X‐ray diffraction, Raman and diffuse reflectance spectroscopy as well as thermal analysis.Item Open Access Pyrido-anellierte 1,2,4,3-Triazaphospholene - ein neuer Zugang und erste Komplexe(2024) Richter, Ferdinand; Gudat, Dietrich (Prof. Dr.)