(A19N7)[In4]2 (A = Ca,Sr) and (Ca4N)[In2]: Synthesis,Crystal Structures,Physical Properties,and Chemical Bonding

Single phase powders of (A₁₉N₇)[In₄]₂ (A = Ca, Sr) and (Ca₄N)[In₂] were prepared by reaction of melt beads of the metallic components with nitrogen. The crystal structure of (Ca₁₉N₇)[In₄]₂ was refined based on neutron and X‐ray powder diffraction data. The crystal structure of (Sr₁₉N₇)[In₄]₂ was solved from the X‐ray powder pattern. The structure refinements in combination with results from chemical analyses ascertain the compositions. The compounds (A₁₉N₇)[In₄]₂ (A = Ca, Sr) are isotypes of (Ca₁₉N₇)[Ag₄]₂; (Ca₁₉N₇)[In₄]₂ is probably identical to the earlier reported (Ca_18.5N₇)[In₄]₂. The crystal structure of the isotypes (A₁₉N₇)[In₄]₂ (A = Ca, Sr; cubic, , Ca: a = 1471.65(3) pm; Sr: a = 1561.0(1) pm) contains isolated [In₄] tetrahedra embedded in a framework of edge‐ and vertex‐sharing (A₆N) octahedra. Six of these octahedra are condensed by edge‐sharing around one central A²⁺ ion to form “superoctahedra” (A₁₉N₆) which are connected three‐dimensionally via further octahedra by corner‐sharing. The crystal structure of (Ca₄N)[In₂] (tetragonal, I4₁/amd, a = 491.14(4) pm, c = 2907.7(3) pm) consists of alternating layers of perovskite type slabs of vertex‐sharing octahedra (Ca₂Ca_4/2N) and parallel arranged infinite zigzag chains equation/tex2gif-stack-1.gif[In₂]. In the sense of Zintl‐type counting the compounds (A²⁺)₁₉(N^3?)₇[(In^2.125?)₄]₂ present an electron excess, (Ca²⁺)₄(N^3?)[(In^2.5?)₂] is electron deficient. Metallic properties are supported by electrical resistivity and magnetic susceptibility measurements. The analysis of the electronic structures gives evidence for the existence of homoatomic interactions In–In and significant heteroatomic metal–metal interactions Ca–In which favor the deviations of the title compounds from the (8 – N) rule.     

Inverse Perovskites (Eu3O)E with E = Sn,In – Preparation,Crystal Structures and Physical Properties

The cubic inverse Perovskites (Eu₃O)In and (Eu₃O)Sn were prepared from the metals and Eu₂O₃ or SnO₂, respectively. For (Eu₃O)In the crystal structure analysis was performed on single crystal X‐ray diffraction data (space group , a = 512.79(3) pm, Z = 1, R_gt(F) = 0.022, wR(F²) = 0.044). The data indicated full occupancy on all sites and a fully ordered structure. According to magnetic susceptibility measurements and X‐ray absorption spectroscopic data at the Eu L_III edge both compounds contain europium in the 4f⁷ (Eu²⁺) electronic state. (Eu₃O)In orders ferromagnetically at 185(5) K, (Eu₃O)Sn shows antiferromagnetic order at 31.4(2) K. Both compounds behave as metallic conductors in electrical resistivity measurements. However, (Eu₃O)In may be classified a metal, while (Eu₃O)Sn is more likely a heavily doped degenerated semiconductor or semimetal according to the absolute values of the resistivity.     

Distribution of dopant metals between PbTiO3 crystals and PbO-B2O3 flux

Single crystals of lead titanate PbTiO₃ doped with silicon, calcium, chromium, manganese, cobalt, nickel, copper, zinc, and cadmium were grown. The compositions and crystallographic parameters of the crystals were studied. The lowest distribution coefficients of dopants between PbTiO₃ crystals and flux were observed with Mn⁺² and Co⁺² and the highest, with Ca⁺². Doping with niobium leads to the formation of solid solutions with the pyrochlore structure A₂B₂O₇ and even higher distribution coefficient. A correlation was found between dopant concentrations and crystal cell parameters.     

Diversity of Strontium Nitridogermanates(IV): Novel Sr4[GeN4], Sr8Ge2[GeN4], and Sr17Ge2[GeN3]2[GeN4]2

Single crystals of three new strontium nitridogermanates(IV) were grown in sealed niobium ampules from sodium flux. Dark red Sr₄[GeN₄] crystallizes in space group P2₁/c with a = 9.7923(2) Å, b = 6.3990(1) Å, c = 11.6924(3) Å and β = 115.966(1)°. Black Sr₈Ge₂[GeN₄] contains Ge^4– anions coexisting with [Ge^IVN₄]^8– tetrahedra and adopts space group Cc with a = 10.1117(4) Å, b = 17.1073(7) Å, c = 10.0473(4) Å and β = 115.966(1)°. Black Sr₁₇Ge₆N₁₄ features the same anions alongside trigonal planar [Ge^IVN₃]^5– units. It crystallizes in P1 with a = 7.5392(1) Å, b = 9.7502(2) Å, c = 11.6761(2) Å, α = 103.308(1)°, β = 94.651(1)° and γ = 110.248(1)°.     

The Quasi‐Binary Acetonitriletriide Sr3[C2N]2

The first quasi‐binary acetonitriletriide Sr₃[C₂N]₂ has been synthesised and characterised. The nearly colourless crystals were obtained from the reaction of Sr metal, graphite, and elemental N₂, generated by decomposition of Sr(N₃)₂, in a sealed Ni ampoule with the aid of an alkali metal flux. The structure of this compound was analysed via single‐crystal X‐ray diffraction and the identity of the [C₂N]^3? anion was confirmed by Raman spectroscopy and further investigated by quantum‐chemical methods. Computed interatomic distances within the [C₂N]^3? anion strikingly match the obtained experimental data.     

Crystal structure investigations of ZrAsxSey (x>y, x+y≤2) by single crystal neutron diffraction at 300 K, 25 K and 2.3 K

Large single crystals of ZrAs_xSe_y (x>y, x+y≤2, PbFCl type of structure, space group P4/nmm) were grown by Chemical Transport. Structural details were studied by single crystal neutron diffraction techniques at various temperatures. One single crystal specimen with chemical composition ZrAs_1.595(3)Se_0.393(1) was studied at ambient temperature (R1=5.10 %, wR2=13.18 %), and a second crystal with composition ZrAs_1.420(3)Se_0.560(1) was investigated at 25 K (R1=2.70%, wR2=5.70 %) and 2.3 K (R1=2.30 %, wR2=4.70 %), respectively. The chemical compositions of the crystals under investigation were determined by wavelength dispersive X-ray spectroscopy. The quantification of trace elements was carried out by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry. According to the crystal structure refinements the crystallographic 2a site is occupied by As, together with a significant amount of vacancies. One of the 2c sites is fully occupied by As and Se (random distribution). With respect to the fractional coordinates of the atoms, the crystal structure determinations based on the data obtained at 25.0 K and 2.3 K did not show significant deviations from ambient temperature results. The temperature dependence of the displacement parameters indicates a static displacement of As on the 2a sites (located on the (0 0 1) planes) for all temperatures. No indications for any occupation of interstitial sites or the presence of vacancies on the Zr (2a) site were found.     

On Copper(I) Fluorides,the Cuprophilic Interaction,the Preparation of Copper Nitride at Room Temperature,and the Formation Mechanism at Elevated Temperatures

Our attempts to synthesize the hitherto unknown binary copper(I) fluoride have led to first successes and a serendipitious result: By conproportionation of elemental copper and copper(II) fluoride in anhydrous liquid ammonia, two copper(I) fluorides were obtained as simple NH₃ complexes. One of them presents an example of ligand‐unsupported “cuprophilic” interactions in an infinite [Cu₂(NH₃)₄]²⁺ chain with alternating Cu–Cu distances. We discovered that both copper(I) fluorides can easily be converted into Cu₃N at room temperature, just by applying a vacuum. Additionally, we investigated the formation mechanism of the classical synthesis route of Cu₃N that starts with CuF₂ and flowing NH₃ in the temperature range between ambient and 290 °C by means of thermal analysis and in situ neutron diffraction. The reaction proceeds at elevated temperatures through the formation of a blue and amorphous ammoniate Cu(NH₃)₂F₂, the reformation of CuF₂, and finally the redox reaction to form Cu₃N.