Volume 77, Issue 6 - Special issue dedicated to Professor Martin Lerch on the occasion of his 60th birthday

The amides Na 3 RE (NH 2 ) 6 have been obtained from the metals in supercritical ammonia under ammonobasic conditions at 573 K and 70 MPa for RE  = La–Nd, and at 473 K and 40 MPa for RE  = Er, Yb. All compounds are formed in the hot zone within a temperature gradient, indicating a retrograde solubility under the applied process conditions. These amides represent soluble intermediates in ammonothermal binary rare earth metal nitride synthesis. All compounds were obtained as microcrystalline powders, while single crystals of those amides containing the heavier rare earth metals could be isolated. The crystal structures were solved and refined from single-crystal and powder X-ray diffraction intensity data. The results of vibrational spectroscopy are reported. Thermal analysis measurements under inert gas atmosphere demonstrated a decomposition to the respective black binary rare earth metal nitrides RE N 1− δ .

The rare earth-rich indides Tm 4 IrIn and Lu 4 PtIn were synthesized by reaction of the elements in sealed tantalum ampules in an induction furnace. Tm 4 IrIn ( a  = 1340.77(4) pm) and Lu 4 PtIn ( a  = 1338.0(1) pm) crystallize with the Gd 4 RhIn-type structure, space group F 4 ‾ 3 m $F\overline{4}3m$ . The Lu 4 PtIn structure was refined from single crystal X-ray diffractometer data: wR  = 0.0524, 517  F 2 values and 20 variables. The striking crystal chemical motif is the fcc packing of In 4 tetrahedra with 318 pm In–In. The Lu 4 PtIn structure is closely related to the structures of Lu 13 Ni 6 In, Lu 14 Pd 3 In 3 and Lu 20 Ir 5 In 3 which all show icosahedral indium coordination and different condensation patterns that build up the indium substructure that consists of a dumbbell in Lu 14 Pd 3 In 3 and a triangle in Lu 20 Ir 5 In 3 . The results of magnetic susceptibility measurements indicate Curie-Weiss paramagnetism for Tm 4 IrIn (7.76(1) µ B per thulium atom) without magnetic ordering down to 2.5 K. Lu 4 PtIn is Pauli-paramagnetic.

Ternary rare-earth hydride oxides (or oxyhydrides) RE HO show rather high thermal stability and inertness in air. SmHO remained intact when stored in air for 12 h, while after storage for one year, it completely hydrolysed to form Sm(OH) 3 . In contrast, YHO and HoHO show only slight decomposition upon longer storage. The cation’s basicity and the air humidity apparently are crucial factors in the air stability of the compounds. Their reactions with various gases were investigated, in order to better understand factors governing the stability in air and to map their potential as precursors in materials synthesis. Both SmHO and YHO reduce CO 2 to carbon and form the metastable C -type rare-earth sesquioxides RE 2 O 3 instead of the thermodynamically stable B -type. YHO reacts with gaseous ammonia to a red powder. By X-ray diffraction, this is identified as yttrium nitride, but the color of the sample suggests it to be an oxygen-poor nitride oxide (oxynitride) phase YN 1− x O x . These results underline the potential of rare-earth hydride oxides as precursors for the synthesis of other rare-earth compounds. The stability in air, even at elevated temperatures of some rare-earth hydride oxides such as YHO and HoHO are advantageous for potential applications as functional materials.

Following up the recently reported example La 3 F 2 Se 2 TaO 4 , colorless needle-shaped single crystals of the new compound La 2 FSeTaO 4 were obtained as an unexpected by-product from solid-state reactions between lanthanum metal, lanthanum trifluoride, lanthanum sesquioxide and selenium in a sodium-chloride flux designed to yield lanthanum oxide fluoride selenides. Silica-jacketed tantalum capsules served as reaction containers at 850 °C, but an undesired activation of the metal tubes led to the formation of a new oxotantalate. La 2 FSeTaO 4 crystallizes orthorhombically in the space group Pnma with the lattice parameters a  = 1146.51(6), b  = 395.16(2) and  c  = 1281.32(7) pm for Z  = 4. The crystallographically unique Ta 5+ cations are surrounded by five oxygen atoms as square pyramids [TaO 5 ] 5– , which share trans -oriented vertices ( d (Ta–O4) = 202 pm, 2×) to form straight ∞ 1 Ta O 1 , 2 , 3 3 / 1 t O 4 2 / 2 v 3 − ${}_{\infty }^{1}\left\{{\left[\text{Ta}{\left.\text{O}1,2,3\right.}_{3/1}^{t}{\left.\text{O}4\right.}_{2/2}^{v}\right]}^{3-}\right\}$ chains propagating along [010] with isotactically aligned tips ( d (Ta–O1) = 183 pm). Embedded into a matrix of lanthanum fluoride selenide according to ∞ 3 La 2 FSe 3 + ${}_{\infty }^{3}\left\{{\left[{\text{La}}_{2}\text{FSe}\right]}^{3+}\right\}$ ( d (La–F) = 236–244 pm, d (La–Se) = 312–318 pm), which consists of two different La 3+ cations as well as singular F − and Se 2− anions, via La–O contacts ( d (La–O) = 247–274 pm), the coordination number of the La 3+ cation towards the anions F − , O 2− and Se 2– amounts to nine with tricapped trigonal prisms or capped square antiprisms as coordination polyhedra models. The tantalum cation has a distant contact with a Se 2− anion ( d (Ta⋯Se) = 317 pm), not efficiently counting to its first coordination sphere, but completing it to a quasi- octahedron.

During attempts to synthesize new platinides in the ternary system Sr–Al–Pt, single crystals of SrAl 5 Pt 3 and Sr 2 Al 16 Pt 9 were obtained from a reaction of the elements with the nominal composition Sr 4 Al 13 Pt 9 . Both orthorhombic structures were refined based on single crystal x-ray diffraction data (SrAl 5 Pt 3 : Pnma , Wyckoff sequence c 9 , a  = 2065.04(7), b  = 413.74(1), c  = 738.98(3) pm, wR 2 = 0.0310, 867 F 2 values, 56 variables; Sr 2 Al 16 Pt 9 : Immm , Wyckoff sequence l 4 j 2 ihga , a  = 416.69(2), b  = 1193.53(6), c  = 1832.38(9) pm, wR 2 = 0.0517, 671 F 2 values, 49 variables); full atomic ordering was observed in both cases. In order to analyze the bonding situation of these new platinides, quantum-chemical calculations were conducted. According to density functional theory both compounds are polar intermetallics with high negative charges on the Pt atoms and covalently bonded [Al 5 Pt 3 ]/[Al 16 Pt 9 ] networks showing strong Pt–Al alongside of weak Al–Al and Pt–Pt bonding.

The synthesis of bis(diphenylphosphino)ethane (dppe) and PMe 3 mono-adducts [(dppe)BeCl 2 ] n and [(PMe 3 )BeCl 2 ] 2 is described and their spectroscopic properties discussed. Hydrolysis of these two compounds and of the bis(diphenylphosphino)propane (dppp) adduct to BeCl 2 gave [dppeH 2 ][BeCl 4 ], [Me 3 PH] n [Be 4 Cl 9 ] n and [dpppH 2 ][Be 2 Cl 6 ], which have been isolated and structurally characterized by single crystal X-ray diffraction. The reactions of [(PMe 3 )BeCl 2 ] 2 with p -cresole gave [Me 3 PH] 2 [Be 2 Cl 4 (OC 7 H 7 ) 2 ]. This phenoxide together with [(Me 3 PO) 2 Be 2 Cl 4 ], the oxidation product of [(PMe 3 )BeCl 2 ] 2 , have also been structurally characterized.

Dark octahedral crystals of K 1− x [Fe 1− x Si x O 2 ] with x  ≈ 0.2 were synthesized under ultra-alkaline conditions in a KOH hydroflux at 200 °C. The compound is a member of the solid solution series between SiO 2 and K[FeO 2 ]. Due to its SiO 2 content, K 0.8 [Fe 0.8 Si 0.2 O 2 ] is much less sensitive to moisture than K[FeO 2 ]. The crystal structure is a stuffed cristobalite with a charged framework of vertex-sharing [ M O 4/2 ] tetrahedra ( M  = Fe 3+ , Si 4+ ) and potassium counter ions in the large voids of the framework. It has the pseudo-symmetry and metrics of the cubic space group F d 3 ‾ m $Fd\overline{3}m$ , but adopts the tetragonal space group I 4 1 md with four formula units in the cell. Unlike other tectosilicates of this type, the [ M O 4/2 ] − tetrahedra are not regular but distorted to disphenoids. The O atom can be modeled by a huge disk-shaped ellipsoid or, better, by split atom positions forming a six-membered ring with a diameter of 1.1 Å. The M –O distances range from 1.66(2) to 1.96(2) Å, the M –O– M angles are 135(2)°, 137(1)°, and 151(1)°.

Ion dynamics in binary Li-bearing compounds such as LiF, Li 2 O and Li 2 S is rather poor. These compounds do, however, form as decomposition products at the interface between the electrolyte and the electrode materials in lithium-based batteries. They are expected to severely influence the charge transport across this electrode-electrolyte interface and, thus, the overall performance of such systems. Yet, ion dynamics in the nanostructured forms of these binary compounds has scarcely been investigated. Here, we prepared bulk nanostructured Li 2 S through high-energy ball milling and studied its temperature-dependent ionic conductivity by means of broadband impedance spectroscopy. It turned out that, compared to the unmilled form, Li +  ion conductivity in ball-milled Li 2 S increased by approximately 3 orders or magnitude. This striking increase is accompanied by a decrease of the average activation energy from ca. 0.9 eV to approximately 0.7 eV. Structural disorder, stress and local distortions are assumed to be responsible for this clear change in macroscopic transport parameters. Fast ion dynamics in or near the interfacial space charge zones might contribute to enhanced dynamics, too. We conclude that Li ion transport in interfacial Li 2 S, if present in a disordered nanostructured form in lithium-ion batteries, is much faster than originally thought for its ordered counterpart.

Sustainable hydrogen production is one of the most challenging topics in modern energy economics. Electrochemical and thermal splitting of water are promising techniques, but are highly energy demanding. Efficient hydrogen evolution reaction catalysts can play a key role to lower the electrolysis potential and to make water splitting more feasible. Among other perovskites, CaMnO 3 has been identified as efficient electrode material due to its relatively high oxygen vacancy concentrations at elevated temperatures. But this compound needs to be further improved for technical use. In this study, the effect of Mn substitution in CaMnO 3 by 3d metals M = Sc, Ti, V, Cr, Fe, Co, Ni, Cu and Zn on the oxygen vacancy formation energy is investigated theoretically at DFT level. Vacancy formation energies, enthalpies and free enthalpies are calculated with a combination of hybrid and GGA density functionals. Configuration entropy is taken into account by calculating all possible configurations of M and oxygen vacancy site in supercell models. The calculated oxygen vacancy formation energies are strongly affected by Mn/M substitution, the most promising heteroelement being Cu. CaMn 0.875 Cu 0.125 O 2.875 and CaMn 0.875 Cu 0.125 O 2.75 are in equilibrium at 537 K, compared to 1231 K for CaMnO 2.875 /CaMnO 2.75 and 1350 K for CaMnO 3 /CaMnO 2.875 .

Phase-pure copper(II) cyanoguanidine bromide hydrate, Cu(C 2 N 4 H 4 ) 2 Br 2 ·2H 2 O ( 1 ), was precipitated from aqueous solution and its structure was solved and refined from single-crystal X-ray diffraction data at 100 K. 1 crystallizes in space group P 2 1 / n with a  = 12.09(3) Å, b  = 3.925(9) Å, c  = 13.79(3) Å, β  = 96.62(6)°, Z  = 2, and V  = 650(2) Å 3 . The copper(II) cation is coordinated by two cyanoguanidine molecules adopting the cyanoimine shape and four bromide anions in a Jahn–Teller-distorted motif, forming infinite chains of edge-sharing octahedra along the crystallographic b axis. IR spectroscopic and magnetic susceptibility measurements were carried out in addition to density-functional electronic-structure calculations performed to assess both the magnetic ground state and the exchange interactions. Experiment and theory agree as regards antiferromagnetism and weak magnetic exchange.

We report the chelation-assisted oxidative CH 2 extrusion from a Pt II -coordinated dipyridylmethane, resulting in the formation of a 2,2′-bipyridyl ligand. This unusual one-pot reaction (solvent: dimethylformamide, DMF), which is quantitative, proceeds in air at mildly elevated temperature, with CH 2 → C=O conversion, decarbonylation, and ipso - ipso C–C coupling of the two pyridyl residues (“fragment coupling”). It constitutes, in effect, a chelate ring contraction by one member.

We have examined the effect of composition on the Raman-active vibrational response of the Cu 2 (Fe x Zn 1− x )SnS 4 and Cu 2 (Mn x Zn 1− x )SnS 4 solid solution series at ambient conditions. Based on these results we were able to identify the phase boundaries of the respective kesterite-type and stannite-type structures adopted by these compounds as a function of composition. In the case of Cu 2 (Fe x Zn 1− x )SnS 4 , our observations correlate very well with earlier reports. For the Cu 2 (Mn x Zn 1− x )SnS 4 series, on the other hand, we were able to clearly pinpoint the kesterite↔stannite transition for intermediate compositions for the first time, indicating that Raman spectroscopy can serve as an efficient method for monitoring subtle structural transitions in these systems.

The synthesis, crystal structures and properties of two alkali metal 3-nitrohydrogenphthalates obtained by a 1:2 reaction of M 2 CO 3 (M = K or Na) with 3-nitrophthalic acid (LH 2 ) are reported. In the anhydrous potassium coordination polymer [K(LH)] (LH = 2-carboxy-3-nitrobenzoate) 1 , the K + cation is bonded to nine oxygen atoms from six symmetry related (LH) – ligands resulting in a distorted {KO 9 } coordination polyhedron. Five of the six oxygen atoms including a nitro oxygen atom of the crystallographically unique 2-carboxy-3-nitrobenzoate are involved in metal binding. The μ 6 -bridging mode of (LH) – places the K + cations into the layers of the two-dimensional (2D) coordination polymer. Each {KO 9 } polyhedron in 1 shares edges with two other polyhedra along the b and c axes. A low temperature structure redetermination of [Na(L # H)(H 2 O) 3 ]·H 2 O (L # H = 2-carboxy-6-nitrobenzoate) 2 has revealed that the (L # H) − anion is bonded to the Na + cation in a monodentate fashion via the carbonyl oxygen atom of the –COOH group and two of the three unique aqua ligands exhibit a bridging bidentate mode stabilizing a chain polymer. The structure of compound 2 thus consists of chains of edge-sharing {NaO 6 } octahedra. Thermal decomposition of 1 or 2 results in the formation of metal carbonate residues.

Modern quantum theory of correlations predicts, and reveals, new counter-intuitive dynamical effects of hydrogen in nano-structured materials, being of considerable importance for basic research as well as for technological applications. To support this claim, here the focus is on H 2 molecules in carbon nanotubes and other nanocavities, as experimentally investigated with the well established technique of incoherent inelastic neutron scattering (INS). In particular, the experimentally determined momentum and energy transfers from an H 2 molecule in a carbon (C-) nanotube resulting in roto-translational motion along the nanotube axis, appear to (1) either violate the standard conservations laws, or (2) attribute the translating H 2 molecule a highly reduced inertia, as quantified by the effective mass M eff  ≈ 0.64 a.m.u. (atomic mass units), instead of 2 a.m.u. for an isolated molecule. This counter-intuitive INS-observation has no conventional interpretation, but it can be qualitatively interpreted “from first principles” in the frame of modern theories of quantumness of correlations and Quantum Thermodynamics (QTD). This analysis also provides a surprising new physical insight: The nano-structured cavities do represent quantum systems which contribute to the quantum dynamics of the hydrogen translational dynamics, and thus to the hydrogen transport in the studied materials. This insight may also have far-reaching consequences for technological applications and material sciences (e.g. fuel cells, H storage materials, etc.), since it concerns the choice and design of “optimized” materials adsorbing or carrying hydrogen.

Reactions of Mn(NCS) 2 with 3-bromopyridine in acetonitrile lead to the formation of Mn(NCS) 2 (3-bromopyridine) 4 ( 1 ) and Mn(NCS) 2 (3-bromopyridine) 2 (MeCN) 2 ( 2 ) that were characterized by single crystal X-ray diffraction. Compounds 1 and 2 consist of discrete complexes, in which the Mn(II) cations are octahedrally coordinated by two trans -N-bonding thiocyanate anions and four pyridine ( 1 ) or two pyridine and two acetonitrile ligands ( 2 ). Thermoanalytical measurements on 1 and 2 have shown that upon heating half of the 3-bromopyridine co-ligands from 1 or both acetonitrile ligands from 2 are removed leading to a crystalline phase with the composition [Mn(NCS) 2 (3-bromopyridine) 2 ] n ( 3-II ). From dry n-butanol a phase with the same composition was obtained ( 3-I ) that corresponds to a polymorphic or isomeric form of 3-II . Crystal structure analysis of 3-I shows that in this form the Mn cations are linked by pairs of anionic ligands into linear chains. The results of magnetic measurements on 3-I show antiferromagnetic interactions along the chains and the analysis of the magnetic susceptibility using the Fisher model for chains gave a J value of −5.76(5) K.

A comprehensive understanding of the nexus of diffusion mechanisms on the atomic scale as well as structural influences on the ionic motion in solid electrolytes is key for further development of high-performing all-solid-state batteries. Therefore, current research not only focuses on the search for innovative materials, but also on the study of diffusion pathways and ion dynamics in ionic conductors. In this context, we report on the extended characterization of the ionic electrolyte Li 6.5 La 3 Zr 1.5 Nb 0.5 O 12 (LLZO-Nb). The commercially available material is analyzed by a combination of powder X-ray (either lab- or synchrotron-based) and neutron diffraction. Details of lithium disorder were obtained from high-resolution neutron diffraction data, from which the ionic transport of Li ions was determined by applying the maximum entropy method in combination with the one-particle potential formalism.

Iron(II) oxide, wüstite, is the iron oxide with the lowest oxygen content. Under ambient conditions it is metastable for two reasons: (1) it undergoes eutectoid decomposition to Fe and Fe 3 O 4 below ≈570° C, and (2) depending on temperature, it is thermodynamically stable only for very low oxygen partial pressures, down to below 10 −20 bar. Hence, for the growth of single crystals from the melt, the growth atmosphere must contain reducing components to keep the oxygen partial pressure on the required low level. With Ar/CO 2 /CO mixtures this aim can be reached. It is shown experimentally and by thermodynamic calculation, that the grown crystals contain carbon inclusions. Theoretically it is shown that wüstite crystals without carbon inclusions could be grown in humid N 2 /H 2 mixtures. First experiments are presented in this article, but a further adjustment of experimental parameters is required.

Electrochemical fluorination in anhydrous HF, also known as the Simons process, is a widely used industrial method for fluorination of organic compounds. Its mechanism, being not so well understood, has long been debated and is believed to involve higher valent nickel fluorides formed on the nickel-plated anode during the process. One of these is speculated to be Ni 2 F 5 , which was previously reported in the literature and assigned via infrared spectroscopy, but its crystal structure is not yet known. We have identified known crystal structures of compounds with similar stoichiometries as Ni 2 F 5 and utilized them as a starting point for our periodic DFT investigations, applying the PBE+U method. Ni 2 F 5 as the most stable polymorph was found to be of the same crystal structure as another mixed valent fluoride, Cr 2 F 5 . The calculated lattice parameters are a  = 7.24 Å, b  = 7.40 Å, c  = 7.08 Å and β  = 118.9° with an antiferromagnetic ordering of the nickel magnetic moments.

Interfacial catalysts are indispensable functional materials in the energy transformation. The traditional empirical search strategies reach their potential. Knowledge-based approaches have not been able to deliver innovative and scalable solutions. Following a short analysis of the origin of these shortcomings a fresh attempt on the material challenge of catalysis is proposed. The approach combines functional understanding of material dynamics derived from operando analysis with digital catalysis science guiding the exploration of non-linear interactions of material genes to catalytic functions. This critically requires the ingenuity of the synthetic inorganic chemist to let us understand the reactivity of well-defined materials under the specific conditions of catalytic operation. It is the understanding of how the kinetics of phase changes brings about and destroys active sites in catalytic materials that forms the basis of realistic material concepts. A rigorous prediction and engineering of these processes may not be possible due to the complexity of options involved.