Die Oxidnitridselenide M3ONSe2 dreiwertiger Lanthanoide (M = Ce – Nd)

The Oxide Nitride Selenides M₃ONSe₂ of Trivalent Lanthanoids (M = Ce – Nd) Oxide nitride selenides of the trivalent lanthanoids (M = Ce – Nd) with the composition M₃ONSe₂ can be prepared by the oxidation of the respective lanthanoid metal with selenium and sodium azide (NaN₃) in presence of impurities containing oxygen when the corresponding lanthanoid trichloride (MCl₃) is used as sodium trap for the coformation of NaCl. The thermal treatment of these mixtures along with additional NaCl as flux at 900 °C in evacuated silica tubes secures the formation of fawn, transparent, lath‐shaped crystals. The monoclinic structure (C2/m, Z = 6) was determined from X‐ray single‐crystal diffraction data (Ce₃ONSe₂: a = 2480.51(14), b = 406.85(3), c = 952.83(6) pm, β = 95.506(4)°; Pr₃ONSe₂: a = 2462.72(14), b = 403.74(3), c = 947.26(6) pm, β = 95.731(4)°; Nd₃ONSe₂: a = 2440.35(14), b = 401.48(3), c = 944.02(6) pm, β = 95.763(4)°). Five crystallographically different M³⁺ cations reside in six‐ to eightfold coordination of the respective anions (three independent O^2?/N^3? and Se^2? each), for which a statistic distribution of the light elements (O^2? : N^3? = 1 : 1) has to be assumed. However, the main features of the crystal structure are (O^2?/N^3?)‐centred (M³⁺)₄ tetrahedra. For the first time ever within the same structure of this kind, condensation of these anion‐centred cation polyhedra forming strands and layers simultaneously could be detected. Cis‐edge connected [(O/N)M₄]^9.5+ tetrahedra build up the chain components running along [010], which are already known as dominating core in some crystal structures of pure nitride chalcogenides (e.g. Sm₄N₂S₃ and Tb₄N₂Se₃). A new motif of condensed tetrahedral units comprises the second feature. By fusing [(O/N)M₄]^9.5+ tetrahedra via vertices and edges, one‐dimensional strand sections from the cationic sheets of the Ce₂O₂S‐type structure, which are further connected only via common vertices to form a lower‐condensed steplike two‐dimensional layer , spreading parallel to the (100) plane, emerge for the very first time.     

Structural Influence of Lone Pairs in GeP2N4, a Germanium(II) Nitridophosphate

Owing to their widespread properties, nitridophosphates are of high interest in current research. Explorative high-pressure high-temperature investigations yielded various compounds with stoichiometry MP₂N₄ (M=Be, Ca, Sr, Ba, Mn, Cd), which are discussed as ultra-hard or luminescent materials, when doped with Eu²⁺. Herein, we report the first germanium nitridophosphate, GeP₂N₄, synthesized from Ge₃N₄ and P₃N₅ at 6 GPa and 800 °C. The structure was determined by single-crystal X-ray diffraction and further characterized by energy-dispersive X-ray spectroscopy, density functional theory calculations, IR and NMR spectroscopy. The highly condensed network of PN₄-tetrahedra shows a strong structural divergence to other MP₂N₄ compounds, which is attributed to the stereochemical influence of the lone pair of Ge²⁺. Thus, the formal exchange of alkaline earth cations with Ge²⁺ may open access to various compounds with literature-known stoichiometry, however, new structures and properties.     

Thermodynamics of Formation of Binary and Ternary Nitrides in the System Ce/Mn/N

Drop solution calorimetry in high‐temperature oxide melts has been shown to be very useful to study the energetics of nitride formation. This methodology was used to determine the enthalpies of formation from the elements of binary and ternary nitrides in the Ce/Mn/N system. The resulting values in kJ mol^–1 are; δH (CeN) = –340.19 ± 6.80, δ(H (Mn₃N_1.95, η‐Mn₃N₂ type) = –192.68 ± 7.57, δH (Mn₆N_5.40, θ‐Mn₆N₅ type) = –430.80 ± 10.93 and δH (Ce₂MnN₃) = –928.18 ± 9.46. The results show the role of inductive effects in Ce₂MnN₃ leading to a higher energetic stability compared to binary components.     

Synthese und Struktur der Nitridoborat‐Nitride Ln4(B2N4)N (Ln = La,Ce) des Formeltyps Ln3+x(B2N4)Nx (x = 0, 1, 2)

Synthesis and Structure of Nitridoborate Nitrides Ln₄(B₂N₄)N (Ln = La, Ce) of the Formula Type Ln_3+x(B₂N₄)N_x (x = 0, 1, 2) The missing member of the formula type Ln_3+x(B₂N₄)N_x with x = 1 was synthesized and characterized for Ln = La and Ce. According to the single‐crystal X‐ray structure solution Ce₄(B₂N₄)N crystallizes in the space group C2/m (Z = 2) with the lattice parameters a = 1238.2(1) pm, b = 357.32(3) pm, c = 905.21(7) pm and β = 129.700(1)°. The anisotropic structure refinement converged at R1 = 0.039 and wR2 = 0.099 for all independent reflections. A powder pattern of La₄(B₂N₄)N was indexed isotypically with a = 1260.4(1) pm, b = 366.15(3) pm, c = 919.8(1) pm and β = 129.727(6)°. A structure rational for nitridoborates and nitridoborate nitrides containing B₂N₄ ions with the general formula Ln_3+x(B₂N₄)N_x with x = 0, 1, 2 is presented.     

Growth and characterization of pendeo-epitaxial GaN on 4H–SiC substrates

Growth on AlN/4H–SiC substrates of coalesced, non-polar GaN films having volumes of material with reduced densities of dislocations and stacking faults has been achieved from etched stripes via the statistical and experimental determination of the effect of temperature and V/III ratio on the lateral and vertical growth rates of the GaN{0 0 0 1} faces combined with pendeo-epitaxy. AFM of the uncoalesced GaN(0 0 0 1) and GaN vertical faces revealed growth steps with some steps terminating at dislocations on the former and a pitted surface without growth steps, indicative of decomposition, on the latter. Coalescence was achieved via (a) a two-step route and the parameters of (1) and V/III=1323 for 40 min and (2) 1020 °C and V/III=660 for 40 min and (b) a one-step route that employed and a V/III ratio=660 for 6 h. The densities of dislocations in the GaN grown vertically over and laterally from the stripes were 4×10¹⁰ cm⁻² and 2×10⁸ cm⁻², respectively; the densities of stacking fault in these volumes were 1×10⁶ cm⁻¹ and 2×10⁴ cm⁻¹, respectively. The defects in the wing material were observed primarily at the bottom of the film where lateral growth of the GaN occurred from the AlN and the SiC. Plan view AFM also revealed different microstructures and a reduction in the RMS roughness values from 1.2 to 0.95 nm in these respective regions.     

Deprotonated 2,3:5,6-Dibenzo-7- aza bicyclo[2.2.1]hepta-2,5-diene as a Nitrido Nitrogen Source by Anthracene Elimination: Synthesis of an Iodide(nitride)chromium(VI) Complex

Instead of azides, which can be explosive and poorly soluble in nonpolar solvents, azabicycloheptadienes can be used to synthesize nitrides. The reaction of diiodide 1 with the lithium amide 3 provides the red nitride 2 in 60 % yield with loss of lithium iodide and anthracene. The remaining iodo ligand in 2 can undergo an exchange reaction with lithium amide 3 , but no more anthracene is released.     

The Mixed-Valent (μ-Nitrido)dimanganese Complex Anion [(CN)5MnV(μ-N)MnII(CN)5]6−

Localized valencies are displayed by the Mn^V–Mn^II complex ion 1 . This is the key finding from X-ray structure analysis, as well as vibrational and EPR spectroscopic invesigations on 1 obtained by the reaction of manganese(II ) and [Mn^v(N)(CN)₅]³⁻ salts in aqueous 1 M NaCN solution. Remarkably, the asymmetry is induced by the nitrogen atom bridge.     

About Binary and Ternary Alkaline Earth Metal Nitrides

Binary and ternary alkaline earth metal nitrides compounds have been synthesized and characterized by the means of X‐ray structure analysis. By the reaction of the alkaline earth metals Be, Mg, and Ca with dry nitrogen, we obtained crystalline material of Be₃N₂ ( 1 ), Mg₃N₂ ( 2 ), and Ca₃N₂ ( 3 ), respectively. For these three compounds we could confirm the cubic anti bixbyite structure (Ia3 (#206); 1 : a = 814.92(1) pm; 2 : 997.26(6) pm and 3 : a = 1147.86(2) pm). By reacting 1 : 2 : 1 mixtures of Ae (Ae = Ca, Sr) : Mg : NaN₃ we synthesized the ternary nitrides CaMg₂N₂ ( 4 ) and SrMg₂N₂ ( 5 ). We confirmed the structural data obtained by Rietveld‐analysis of X‐ray powder diffraction data for 4 and found 5 to be isotypic (anti‐C–M₂O₃ structure, trigonal, P 3ml (#164); 4 : a = 354.77(5) pm, c = 609.60(12) pm; 4 : a = 362.20(5), c = 635.90(13) pm). The indexing of the powder diffractogram of “Ca₃Mg₃N₄” and refining the lattice parameters (hexagonal, a = 352.9(2) and c = 607.5(5) pm) suggest its identity with 4 . The black “low‐temperature phase of Ca₃N₂” has been synthesized and and the X‐ray powder diffractogram has been recorded. The reactions of this phase are also described. The yellow “high‐temperature phase of Ca₃N₂” was found to be Ca₄N₂(CN₂).     

Synthesis,Crystal Structure,and Physical Properties of (Ca3N)Tl

Single crystals of (Ca₃N)Tl (Pm 3 m, No. 221, a = 4.9851(3) Å; Z = 1) with a metallic luster and black single phase powders of the ternary nitride were obtained from reactions of the respective metals with nitrogen at maximum temperatures of 950 °C. (Ca₃N)Tl crystallizes in an antiperovskite‐type arrangement. The magnetic susceptibility is nearly temperature independent (+170(10) · 10^–6 emu/mol). Metallic behavior is supported by band structure calculations on the LDA LMTO‐ASA level of theory. Chemical bonding is analyzed and the results are compared with the isotypic nitrides (Ca₃N)Pb and (Ca₃N)Bi.     

The Hexanitridodimanganate(IV) Li6Ca2[Mn2N6]: Preparation,Crystal Structure,and Chemical Bonding

Unbridged Mn ₂ units are present in the hexanitridodimanganate(IV ) ions of the title compound. This is the first example of a Mn–Mn single bond within a complex anion in which the manganese centers have the high oxidation state +4. According to ELF calculations, the Mn–Mn bond can be regarded as a two-electron, two-center bond.