03 Fakultät Chemie
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Item Open Access Confirmation of siderazot, Fe3N1.33, the only terrestrial nitride mineral(2021) Bette, Sebastian; Theye, Thomas; Bernhardt, Heinz-Jürgen; Clark, William P.; Niewa, RainerSiderazot, the only terrestrial nitride mineral, was reported only once in 1876 to occur as coating on volcanic rocks in a fumarolic environment from Mt. Etna and, to date, has been neither confirmed nor structurally characterized. We have studied the holotype sample from the Natural History Museum, London, UK, originally collected by O. Silvestri in 1874, and present siderazot with epsilon-Fe3N-type crystal structure and composition of Fe3N1.33(7) according to crystal structure Rietveld refinements, in good agreement with electron microprobe analyses. Crystal structure data, chemical composition, and Raman and reflectance measurements are reported. Possible formation conditions are derived from composition and phase stability data according to synthetic samples.Item Open Access Mixed valency vs radical bridge formulation in symmetrically and asymmetrically ligated diruthenium complexes(2022) Mondal, Sudipta; Schwederski, Brigitte; Záliš, Stanislav; Kaim, WolfgangThe asymmetrical dinuclear [{(trpy*)Ru}2(μ‐adc‐Salph)Cl](PF6) 1(PF6), trpy*=4,4’,4”‐tri‐tert‐butyl‐2,6,2’,6”‐terpyridine, adc‐Salph=1‐benzoyl‐2‐salicyloylhydrazido(3‐), and the related symmetrical dinuclear [{Cl(trpy*)Ru}2(μ,η2 : η2‐adc‐Ph)](PF6) 2(PF6), adc‐Ph=1,2‐bis(benzoyl)hydrazido(2‐), were synthesized and structurally characterized. Both paramagnetic compounds were compared with the previously reported symmetrical [{(trpy*)Ru}2(μ,η3 : η3‐adc‐Sal)](PF6) 3(PF6) containing the bis‐tridentate bridge 1,2‐bis(salicyloyl)hydrazido(4‐). Molecular structures and magnetic resonance features (1H NMR, EPR) indicate spin density distribution over the metal(s) and the bridging ligand. Reversible one‐electron reduction and oxidation were possible in all instances yielding comproportionation constants Kc of about 109 for the paramagnetic intermediates 1+-3+. Structural results, spin density distribution and UV‐Vis‐NIR spectroelectrochemistry were analyzed for 1+ with the help of TD‐DFT calculations for a model compound (tert‐Bu→Me). Intense absorptions around λmax=1450-1650 nm for the cations were assigned to mixed metal/ligand transitions with significant inter‐valence charge transfer (IVCT) character. For both the symmetrical and asymmetrical arrangements the cationic intermediates can be described as considerably mixed metal/ligand systems.Item Open Access The reduced nitridogermanates(III) Ca6[Ge2N6] and Sr6[Ge2N6] with Ge-Ge bonds(2021) Link, Lukas; Pathak, Manisha; Jach, Franziska; Koželj, Primoz; Ormeci, Alim; Höhn, Peter; Niewa, RainerThe first nitridogermanates(III) Ca6[Ge2N6] and Sr6[Ge2N6] were synthesized from sodium flux and structurally characterized by powder and single crystal X‐ray diffraction, respectively. They crystallize isostructurally to each other and homeotypic to Ca6[Cr2N6]H in space group R3‾. They feature unprecedented, mutually isolated, ethane‐like [GeIII2N6]12- anions in a staggered conformation. The compounds are semiconductors according to resistivity measurements and electronic structure calculations, yielding band gaps of 1.1 eV for Ca6[Ge2N6] and 0.2 eV for Sr6[Ge2N6].Item Open Access Mesoionic imines (MIIs) : strong donors and versatile ligands for transition metals and main group substrates(2022) Rudolf, Richard; Neuman, Nicolás I.; Walter, Robert R. M.; Ringenberg, Mark. R.; Sarkar, BiprajitWe report the synthesis and the reactivity of 1,2,3‐triazolin‐5‐imine type mesoionic imines (MIIs). The MIIs are accessible by a base‐mediated cycloaddition between a substituted acetonitrile and an aromatic azide, methylation by established routes and subsequent deprotonation. C=O‐stretching frequencies in MII-CO2 and -Rh(CO)2Cl complexes were used to determine the overall donor strength. The MIIs are stronger donors than the N‐heterocyclic imines (NHIs). MIIs are excellent ligands for main group elements and transition metals in which they display substituent‐induced fluorine‐specific interactions and undergo C-H activation. DFT calculations gave insights into the frontier orbitals of the MIIs. The calculations predict a relatively small HOMO-LUMO gap compared to other related ligands. MIIs are potentially able to act as both π‐donor and π‐acceptor ligands. This report highlights the potential of MIIs to display exciting properties with a huge potential for future development.Item Open Access Indium ammoniates from ammonothermal synthesis : InAlF6(NH3)2, [In(NH3)6][AlF6], and [In2F(NH3)10]2[SiF6]5 ∙ 2 NH3(2021) Becker, Peter; Cekovski, Toni Boris; Niewa, RainerThe ammonothermal synthesis of three ammoniates of indium, namely InAlF6(NH3)2, [In(NH3)6][AlF6], and [In2F(NH3)10]2[SiF6]5 ∙ 2 NH3 was successful from near-ammononeutral conditions in the presence of fluoride ions. Initially, all these compounds were obtained upon corrosion of the applied liner and crucible material Si3N4, which also contains small amounts of aluminum. The syntheses were performed in supercritical ammonia (T = 753 K, p up to 307 MPa). The crystal structures were solved and refined from single crystal X-ray diffraction intensity data. InAlF6(NH3)2 crystallizes as a typical layer-type structure with corner-sharing [InF4(NH3)2]- and [AlF6]3- octahedra. [In(NH3)6][AlF6] features isolated [In(NH3)6]3+ and [AlF6]3- octahedra. The crystal structure of [In2F(NH3)10]2[SiF6]5 ∙ 2 NH3 contains [(NH3)5In-F-In(NH3)5]5+ octahedra doubles next to [SiF6]2- octahedra and ammonia molecules. All intermediates have strong hydrogen bonding systems. The results from vibrational spectroscopy are reported.Item Open Access Tetra-μ3-iodido-tetrakis[(tri-n-butylphosphane-κP)copper(I)](2014) Klenk, Simon; Frey, Wolfgang; Bubrin, Martina; Laschat, SabineTetrameric phosphane complexes of copper(I) halides are extensively used as reagents for copper-mediated conjugate additions. Furthermore, theoretical interest stems from the fact that all group 11 elements in the oxidation state +1 are prone to form clusters with potential metal-metal distances. Thus, theoretical work on such complexes (XCuPR3)4 has been carried out to study structures and stabilities in detail. However, the plethora of structural information on these compounds came from X-ray crystal structure analyses. Although the known tri-n-butyl phosphane complex [n-Bu3PCuI]4 had already been characterized by using X-ray crystallography, no atomic coordinates, bond lengths or bond angles were reported. Thus, we reinvestigated the crystal structure of [n-Bu3PCuI]4. We were able to confirm the previously postulated tetrameric complex with a distorted heterocubane structure similar to the AsEt3 derivative.Item Open Access Magnetic and structural properties of barium hexaferrite BaFe12O19 from various growth techniques(2017) Vinnik, Denis A.; Tarasova, Aleksandra Yu.; Zherebtsov, Dmitry A.; Gudkova, Svetlana A.; Galimov, Damir M.; Zhivulin, Vladimir E.; Trofimov, Evgeny A.; Nemrava, Sandra; Perov, Nikolai S.; Isaenko, Ludmila I.; Niewa, RainerBarium hexaferrite powder samples with grains in the m-range were obtained from solid-state sintering, and crystals with sizes up to 5 mm grown from PbO, Na2CO3, and BaB2O4 fluxes, respectively. Carbonate and borate fluxes provide the largest and structurally best crystals at significantly lower growth temperatures of 1533 K compared to flux-free synthesis (1623 K). The maximum synthesis temperature can be further reduced by the application of PbO-containing fluxes (down to 1223 K upon use of 80 at % PbO), however, Pb-substituted crystals Ba1-xPbxFe12O19 with Pb contents in the range of 0.23(2) x 0.80(2) form, depending on growth temperature and flux PbO content. The degree of Pb-substitution has only a minor influence on unit cell and magnetic parameters, although the values for Curie temperature, saturation magnetization, as well as the coercivity of these samples are significantly reduced in comparison with those from samples obtained from the other fluxes. Due to the lowest level of impurities, the samples from carbonate flux show superior quality compared to materials obtained using other methods.Item Open Access Scheelite-type sodium neodymium(III) ortho-oxidomolybdate(VI), NaNd[MoO4]2(2011) Schleid, Thomas; Hartenbach, IngoThe crystal structure of Scheelite-type NaNd[MoO4]2 is described in the paper.Item Open Access New crystal structures of rare‐earth metal(III) oxotellurates(IV) RE2Te3O9: A1‐type (RE=La, Ce) and A2‐type (RE=Pr, Nd)(2021) Chou, Sheng‐Chun; Höss, Patrick; Russ, Philip L.; Strobel, Sabine; Schleid, ThomasThe new rare-earth metal(III) oxotellurates(IV) RE2Te3O9 (RE=La-Nd) of the so far unknown A-type structure can be obtained as needle-shaped single crystals through solid-state reactions of the corresponding binary oxides. Their crystal structures were determined as A1-type for RE=La and Ce or A2-type for RE=Pr and Nd by single-crystal X-ray diffraction. Both structure types crystallize in the monoclinic crystal system, but in two different non-centrosymmetric space groups: the A1-type with Z=8 in space group P21 (La2Te3O9: a=569.54(3), b=2230.12(13), c=1464.71(4) pm, β=101.205(3)°; Ce2Te3O9: a=567.02(3), b=2222.61(13), c=1457.13(9) pm, β=101.134(3)°) or the A2-type with Z=16 in space group Cc (Pr2Te3O9: a=2838.61(16), b=563.89(3), c=2522.08(15) pm, β=118.816(3)°; Nd2Te3O9: a=2826.38(16), b=561.47(3), c=2511.94(15) pm, β=118.841(3)°). In spite of the differences in the unit-cell parameters and the symmetry, both structures consist of quite similar fundamental building blocks (FBBs) consisting of eight crystallographically distinct rare-earth metal-oxygen polyhedra with C.N.(RE3+) from seven to nine and always twelve different ψ1-tetrahedral oxotellurate(IV) anions [TeO3]2-, which show a high number of secondary bonding interactions (SBIs) with each other in all four cases.Item Open Access On the thermal dimorphy of the strontium perrhenate Sr[ReO4]2(2024) Conrad, Maurice; Bette, Sebastian; Dinnebier, Robert E.; Schleid, ThomasHygroscopic single crystals of a new hexagonal high‐temperature modification of Sr[ReO4]2 were prepared from a melt of Sr[ReO4]2 ⋅ H2O and SrCl2 ⋅ 6 H2O. The structure analysis of the obtained crystals by X‐ray diffraction revealed that the title compound crystallizes in the ThCd[MoO4]3‐type structure with the hexagonal space group P63/m and the lattice parameters a=1023.81(7) pm and c=646.92(4) pm (c/a=0.632) for Z=2 in its quenchable high‐temperature form. Two crystallographically independent Sr2+ cations are coordinated by oxygen atoms forming either octahedra or tricapped trigonal prisms, whereas the Re7+ cations are found in the centers of discrete tetrahedral meta‐perrhenate units [ReO4]-. Temperature‐dependent in‐situ PXRD studies of dry powder samples of Sr[ReO4]2 exhibited its thermal dimorphy with a phase‐transition temperature at 500-550 °C from literature‐known m‐Sr[ReO4]2 into the newly discovered h‐Sr[ReO4]2 (hexagonal).