Synthesis and Crystal Structure of the Nitridosilicates Ca5[Si2N6] and Ca7[NbSi2N9]

Ca₅[Si₂N₆] and Ca₇[NbSi₂N₉] were obtained by reaction of Ca₃N₂, Ca₂N and Si₃N₄ (with addition of niobium powder in case of Ca₇[NbSi₂N₉]) in closed tantalum ampoules at temperatures at 1060 °C and 1000 °C, respectively. Ca₅[Si₂N₆] is monoclinic C2/c with a = 983.6(2) pm, b = 605.2(1) pm, c = 1275.7(3), β = 100.20(3)° and Z = 4 crystallising homotypically to Ba₅[Si₂N₆]. The crystal structure contains pairs of edgesharing SiN₄ tetrahedra forming isolated nitridosilicate anions of [Si₂N₆]^10?. Ca₇[NbSi₂N₉] is monoclinic P2₁/m with a = 605.1(1), b = 994.6(2), c = 899.7(2), β = 92.10(1)°, Z = 2 and crystallises in an hitherto unknown structure type. Ca₇[NbSi₂N₉] contains isolated anions [NbSi₂N₉]^14? which are composed of two edgesharing SiN₄ tetrahedra and an edge‐sharing NbN₅ pyramid. So far, such a pseudotrisilicate unit has not been observed in the family of silicates.     

Li4Ca3Si2N6 and Li4Sr3Si2N6 – Quaternary Lithium Nitridosilicates with Isolated [Si2N6]10– Ions

The isotypic nitridosilicates Li₄Ca₃Si₂N₆ and Li₄Sr₃Si₂N₆ were synthesized by reaction of strontium or calcium with Si(NH)₂ and additional excess of Li₃N in weld shut tantalum ampoules. The crystal structure, which has been solved by single‐crystal X‐ray diffraction (Li₄Sr₃Si₂N₆: C2/m, Z = 2, a = 6.1268(12), b = 9.6866(19), c = 6.2200(12) Å, β = 90.24(3)°, wR₂ = 0.0903) is made up from isolated [Si₂N₆]^10– ions and is isotypic to Li₄Sr₃Ge₂N₆. The bonding angels and distances within the edge‐sharing [Si₂N₆]^10– double‐tetrahedra are strongly dependent on the lewis acidity of the counterions. This finding is discussed in relation to the compounds Ca₅Si₂N₆ and Ba₅Si₂N₆, which also exhibit isolated [Si₂N₆]^10– ions.     

Sm4S3[Si2O7] und NaSm9S2[SiO4]6: Zwei Sulfidsilicate mit dreiwertigem Samarium

Sm₄S₃[Si₂O₇] and NaSm₉S₂[SiO₄]₆: Two Sulfide Silicates with Trivalent Samarium The sulfide silicates Sm₄S₃[Si₂O₇] and NaSm₉S₂[SiO₄]₆ are obtained as light yellow transparent crystals by the reaction of Sm, Sm₂O₃, S, and SiO₂ with fluxing SmCl₃ or NaCl, respectively, in suitable molar ratios in fused evacuated silica tubes (850 °C, 7 d). Tetragonal crystals of Sm₄S₃[Si₂O₇] (I4₁/amd; Z = 8; a = 1186.4(1); c = 1387.0(2) pm) with ecliptically conformed [Si₂O₇]^6–‐groups of corner sharing [SiO₄]‐tetrahedra are formed. These double tetrahedra as well the sulfide anions (S^2–) coordinate two crystallographically independent metal cations. They provide coordination numbers of 8 + 1 (5 S^2– and 3 + 1 O^2–) for Sm1 and 9 (3 S^2– and 6 O^2–) for Sm2. NaSm₉S₂[SiO₄]₆ crystallizes hexagonally (P6₃/m; Z = 1; a = 975.32(9); c = 676.46(7) pm) in a modified bromapatite‐type structure. The coordination spheres about the two crystallographically different Sm³⁺ cations are built up by oxygen atoms of the orthosilicate units ([SiO₄]^4–) and sulfide anions (S^2–). As a result, Sm1 and Sm2 have coordination numbers of 9 and 8, respectively. Na⁺ and (Sm1)³⁺ occupy the position 4 f in a molar ratio of 1 : 3 whereas the lower coordinated (Sm2)³⁺ occupies the 6 h position.     

[Si4]4– and [Si9]4– Clusters Crystallized from Liquid Ammonia Solution – Synthesis and Characterization of K8[Si4][Si9]·(NH3)14.6

The extraction of the silicide K₁₂Si₁₇ with liquid ammonia in the presence of a sequestering agent and AuPPh₃Cl or Zn(Cp*)₂ led to crystals of the solvate compound K₈[Si₄][Si₉] · (NH₃)_14.6, which was characterized by single‐crystal X‐ray diffraction. It is the first compound with an isolated and ligand‐free [Si₄]^4– cluster obtained from solution. It also contains one [Si₉]^4– cluster per formula unit, whereas the precursor K₁₂Si₁₇ is built from [Si₄]^4– and [Si₉]^4– clusters with a 2:1 ratio.     

Ca12[Mn19N23] and Ca133[Mn216N260]: Structural Complexity by 2D Intergrowth

Two new calcium nitridomanganates, Ca₁₂[Mn₁₉N₂₃] (P3, a=11.81341(3) Å, c=5.58975(2) Å, Z=1) and Ca₁₃₃[Mn₂₁₆N₂₆₀] ( , a=39.477(1) Å, c=5.5974(2) Å, Z=1), were obtained by a gas–solid reaction of Ca₃N₂ and Mn with N₂ at 1273 K and 1223 K, respectively. The crystal structure of Ca₁₂[Mn₁₉N₂₃] was determined from high‐resolution X‐ray synchrotron powder diffraction data, whereas single‐crystal X‐ray diffraction was employed to establish the crystal structure of the Ca₁₃₃[Mn₂₁₆N₂₆₀] phase, which classifies as a complex metallic alloy (CMA). Both crystal structures have 2D nitridomanganate layers containing similar building blocks but of different levels of structural complexity. Bonding analysis as well as magnetic susceptibility and electron spin resonance measurements revealed that only a fraction of the Mn atoms in both structures carries a localized magnetic moment, while for most Mn species the magnetism is quenched as a result of metal–metal bond formation.     

Pr10[Si10−xAlxO9+xN17−x]Cl with x ≈ 1 – an Oxonitridoaluminosilicate Chloride

The oxonitridoaluminosilicate chloride Pr₁₀[Si_10?xAl_xO_9+xN_17?x]Cl was obtained by the reaction of praseodymium metal, the respective chloride, AlN and Al(OH)₃ with “Si(NH)₂” in a radiofrequency furnace at temperatures around 1900 °C. The crystal structure was determined by single‐crystal X‐ray diffraction (Pbam, no. 55, Z = 2,a = 10.5973(8) Å, b = 11.1687(6) Å, c = 11.6179(7) Å, R1 = 0.0337). The sialon crystallizes isotypically to the oxonitridosilicate halides Ce₁₀[Si₁₀O₉N₁₇]Br, Nd₁₀[Si₁₀O₉N₁₇]Br and Nd₁₀[Si₁₀O₉N₁₇]Cl, which represent a new layered structure type. The structure refinement was performed utilizing an O/N‐distribution model according to Paulings rules, i.e. nitrogen was positioned on all bridging sites and mixed O/Noccupation was assumed on the terminal sites resulting in charge neutrality of the compounds. The Si and Al atoms were refined equally distributed on their three crystallographic sites, due to their poor distinguishability by X‐ray analysis. The tetrahedra layers of the structure consist of condensed [(Si,Al)N₂(O,N)₂] and [(Si,Al)N₃(O,N)] tetrahedra of Q² and Q³ type. The chemical composition of the compound was derived from electron probe micro analyses (EPMA).     

Y23Sr17[Si38O18N67]O9 – An Oxonitridosilicate Oxide with a Unique Layered Structure

The oxonitridosilicate oxide Y₂₃Sr₁₇[Si₃₈O₁₈N₆₇]O₉ was synthesized in a radiofrequency furnace at 1450 °C starting from YF₃, Y₂O₃, SrH₂ and silicon diimide. The driving force of the metathesis reaction is probably the simultaneous formation of SrF₂ and H₂. The crystal structure was solved and refined from single‐crystal X‐ray diffraction data in space group P6₃/m (no. 176) with a = 16.5764(4), c = 18.6177(5) Å, and Z = 2 (R₁ = 0.0196, wR₂ = 0.0377). The results are supported by Rietveld refinement on X‐ray powder data, X‐ray spectroscopy, and IR spectroscopy. The crystal structure contains [Si₃₈O₁₈N₆₇]^85– layers built up of vertex‐sharing SiN₄ and SiON₃ tetrahedra. Lattice energy (MAPLE) and charge distribution (CHARDI) calculations indicate anion and cation ordering, with the exception of one mixed occupied Y/Sr site. UV/Vis spectroscopy and DFT calculations yield an optical optical bandgap of 3.8 eV and an electronic bandgap of 3.6 eV, respectively.     

Ce10[Si10O9N17]Br, Nd10[Si10O9N17]Br and Nd10[Si10O9N17]Cl oxonitridosilicate halides with a new layered structure type

The isotypic oxonitridosilicate halides Ce₁₀[Si₁₀O₉N₁₇]Br, Nd₁₀[Si₁₀O₉N₁₇]Br and Nd₁₀[Si₁₀O₉N₁₇]Cl were obtained by the reaction of the respective lanthanide metals, their oxides and halides with “Si(NH)₂” in a radiofrequency furnace at temperatures around 1800 °C, using CsBr, resp. CsCl, as a flux. The crystal structures were determined by single-crystal X-ray diffraction (Pbam, no. 55, Z=2; Ce/Br: a=10.6117(9) Å, b=11.2319(10) Å, c=11.688(8) Å, R1=0.0356; Nd/Br: a=10.523(2) Å, b=11.101(2) Å, c=11.546(2) Å, R1=0.0239; Nd/Cl: a=10.534(2) Å, b=11.109(2) Å, c=11.543(2) Å, R1=0.0253) and represent a new layered structure type. The structure refinements were performed utilizing an O/N-distribution model according to Paulings rules, i.e. nitrogen was positioned on all bridging sites and mixed O/N-occupation was assumed on the terminal sites resulting in charge neutrality of the compounds. The layers consist of condensed [SiN₂(O/N)₂] and [SiN₃(O/N)] tetrahedra of Q² and Q³ type. The chemical composition of the compounds was derived from chemical analyses for Nd₁₀[Si₁₀O₉N₁₇]Br and electron probe micro analyses (EPMA) for all three compounds. The results of IR spectroscopic investigations are reported.     

Neue Vertreter des Er6[Si11N20]O‐Strukturtyps Hochtemperatur‐Synthesen und Kristallstrukturen von Ln(6+x/3)[Si(11–y)AlyN(20+x–y)]O(1–x+y) mit Ln = Nd,Er, Yb,Dy und 0 ≤ x ≤ 3, 0 ≤ y ≤ 3

New Representatives of the Er₆[Si₁₁N₂₀]O Structure Type. High‐Temperature Synthesis and Single‐Crystal Structure Refinement of Ln_(6+x/3)[Si_(11–y)Al_yN_(20+x–y)]O_(1–x+y) with Ln = Nd, Er, Yb, Dy and 0 ≤ x ≤ 3, 0 ≤ y ≤ 3 According to the general formula Ln_(6+x/3)[Si_(11–y)Al_yN_(20+x–y)]O_(1–x+y) (0 ≤ x ≤ 3, 0 ≤ y ≤ 3) four nitridosilicates, namely Er₆[Si₁₁N₂₀]O, Yb_6.081[Si₁₁N_20.234]O_0.757, Dy_0.33Sm₆[Si₁₁N₂₀]N, and Nd₇[Si₈Al₃N₂₀]O were synthesized in a radiofrequency furnace at temperatures between 1300 and 1650 °C. The homeotypic crystal structures of all four compounds were determined by single‐crystal X‐ray diffraction. The nitridosilicates are trigonal with the following lattice constants: Er₆[Si₁₁N₂₀]O: a = 978.8(4) pm, c = 1058.8(3) pm; Yb_6.081[Si₁₁N_20.243]O_0.757: a = 974.9(1) pm, c = 1055.7(2) pm; Dy_0.33Sm₆[Si₁₁N₂₀]N: a = 989.8(1) pm, c = 1078.7(1) pm; Nd₇[Si₈Al₃N₂₀]O: a = 1004.25(9) pm, c = 1095.03(12) pm. The crystal structures were solved and refined in the space group P31c with Z = 2. The compounds contain three‐dimensional networks built up by corner sharing SiN₄ and AlN₄ tetrahedra, respectively. The Ln³⁺ and the “isolated” O^2– ions are situated in the voids of the structures. According to Ln_(6+x/3)[Si_(11–y)Al_yN_(20+x–y)]O_(1–x+y) an extension of the Er₆[Si₁₁N₂₀]O structure type has been found.     

Crystal Structure,Phase Transition and Ferroelastic Properties of [N(CH3)4]3[As2Cl9]

The crystal structure of [N(CH₃)₄]₃[As₂Cl₉] is determined at 293 K. It crystallizes in trigonal space group P31c: a = 9.2199(8), c = 21.065(3)Å, Z = 2, R₁ = 0.0505, wR₂ = 0.1283. The crystal is built of the discrete bioctahedral [As₂Cl₉]^3— anions and the deformed tetramethylammonium cations. A structural phase transition in [N(CH₃)₄]₃[As₂Cl₉] is detected by the DSC and dilatometric techniques at 146/151 K (on cooling/heating). Dielectric relaxation studies in the frequency range 75 kHz — 5 MHz indicate reorientations of the tetramethylammonium cations within the high temperature phase. Optical observations show the existence of the ferroelastic domain structure below 146 K. The possible mechanism of phase transition is discussed on the basis of the presented results.     

Die neuen Schichtsilicate Ba3Si6O9N4 und Eu3Si6O9N4

The New Layer‐Silicates Ba₃Si₆O₉N₄ and Eu₃Si₆O₉N₄ The new oxonitridosilicate Ba₃Si₆O₉N₄ has been synthesized in a radiofrequency furnace starting from BaCO₃, amorphous SiO₂ and Si₃N₄. The reaction temperature was at about 1370 °C. The structure of the colorless compound has been determined by single‐crystal X‐ray diffraction analysis (Ba₃Si₆O₉N₄, space group P3 (no. 143), a = 724.9(1) pm, c = 678.4(2) pm, V = 308.69(9)· 10⁶ pm³, Z = 1, R1 = 0.0309, 1312 independent reflections, 68 refined parameters). The compound is built up of corner sharing SiO₂N₂ tetrahedra forming corrugated layers between which the Ba²⁺ ions are located. Substitution of barium by europium leads to the isotypic compound Eu₃Si₆O₉N₄. Because no single‐crystals could be obtained, a Rietveld refinement of the powder diffractogram was conducted for the structure refinement (Eu₃Si₆O₉N₄, space group P3 (no. 143), a = 711.49(1) pm, c = 656.64(2) pm, V = 287.866(8) ·10⁶ pm³, R_p = 0.0379, R_F² = 0.0638). The ²⁹Si MAS‐NMR spectrum of Ba₃Si₆O₉N₄ shows two resonances at ?64.1 and ?66.0 ppm confirming two different crystallographic Si sites.     

Synthesis,Crystal and Electronic Structure of the Nitridoaluminosilicate Ca5[Si2Al2N8]

Ca₅[Si₂Al₂N₈] was synthesized from elementary aluminum and silicon with phase‐pure tricalcium dinitride at 1280 K under dry argon in a sealed niobium ampoule. Ca₃N₂ was freshly prepared from distilled calcium metal in a dry nitrogen atmosphere. The compound crystallizes in form of transparent yellow distorted octahedra. In air and under moisture Ca₅[Si₂Al₂N₈] undergoes hydrolysis. The structure was determined from a single crystal to be orthorhombic (space group Pbcn – no. 60, a = 925.5, b = 614.0 and c = 1557.8 pm). The nitridoaluminate and ‐silicate substructures are separated into planes of edge and corner‐shared aluminate tetrahedra, which are linked by edge‐sharing double tetrahedral pillars of the silicate. The structure was confirmed by electrostatic and quantum mechanical analysis.     

Pr4S3[Si2O7] und Pr3Cl3[Si2O7]: Durch weiche Fremdanionen modifizierte Derivate von Praseodymdisilicat

Pr₄S₃[Si₂O₇] and Pr₃Cl₃[Si₂O₇]: Derivatives of Praseodymium Disilicate Modified by Soft Foreign Anions For synthesizing both the disilicate derivatives Pr₄S₃[Si₂O₇] and Pr₃Cl₃[Si₂O₇], Pr, Pr₆O₁₁ and SiO₂ are brought to reaction with S and PrCl₃, respectively, in suitable molar ratios (850 °C, 7 d) in evacuated silica tubes. By using NaCl as a flux, Pr₄S₃[Si₂O₇] crystallizes as pale green, transparent single crystals (tetragonal, I4₁/amd, a = 1201.6(1), c = 1412.0(2) pm, Z = 8) with the appearance of slightly compressed octahedra. On the other hand, Pr₃Cl₃[Si₂O₇] emerges as pale green, transparent platelets and crystallizes monoclinically (space group: P2₁, a = 530.96(6), b = 1200.2(1), c = 783.11(8) pm, β = 109.07(1)°, Z = 2). In both crystal structures ecliptically conformed [Si₂O₇]^6– units of two corner‐linked [SiO₄] tetrahedra with Si–O–Si bridging angles of 131° in the sulfide and 148° in the chloride disilicate are present. In Pr₄S₃[Si₂O₇] both crystallographically independent Pr³⁺ cations show coordination numbers of 8 + 1 (5 S^2– and 3 + 1 O^2–) and 9 (3 S^2– and 6 O^2–). For Pr1, Pr2 and Pr3 in Pr₃Cl₃[Si₂O₇] coordination numbers of 10 (5 Cl^– and 5 O^2–) and 9 (2 ×; 4 Cl^– and 5 O^2– or 3 Cl^– and 6 O^2–, respectively) occur.     

Magnetic Investigations and 151Eu Mössbauer Spectroscopy of MYbSi4N7 with M = Sr,Ba, Eu

The isotypic nitridosilicates MYb[Si₄N₇] (M = Sr, Ba, Eu) were obtained by the reaction of the respective metals with Si(NH)₂ in a radiofrequency furnace below 1600 °C. On the basis of powder diffraction data of MYb[Si₄N₇] Rietveld refinements of the lattice constants were performed; these confirmed the previously published single‐crystal data. The compounds contain a condensed network of corner‐sharing [N(SiN₃)₄] units. The central nitrogen thus exhibits ammonium character. Magnetic susceptibility measurements of MYb[Si₄N₇] (M = Sr, Ba, Eu) show paramagnetic behavior with experimental magnetic moments of 3.03(2), (Sr), 2.73(2) (Ba), and 9.17(2) (Eu) μ_B per formula unit. In EuYbSi₄N₇ the europium and ytterbium atoms are in stable divalent and trivalent states, respectively. According to the non‐magnetic character of the alkaline earth cations, ytterbium has to be in an intermediate valence state Yb^III‐x in the strontium and barium compound. Consequently, either a partial exchange N^3—/O^2— resulting in compositions MYb^III‐x[Si₄N_7—xO_x] or an introduction of anion defects according to MYb^III‐x[Si₄N_7—x/3□_x/3] has to be assumed. The phase width 0 ≤ x ≤ 0.4 was estimated according to the magnetic measurements. ¹⁵¹Eu Mössbauer spectra of EuYb[Si₄N₇] at 78 K show a single signal at an isomer shift of δ = —12.83(3) mm s^—1 subject to quadrupole splitting of ΔE_Q = 5.7(8) mm s^—1, compatible with purely divalent europium.     

Nitrido-silicate. III. Hochtemperatur-Synthese,Kristallstruktur und magnetische Eigenschaften von Ce3[Si6N11]

Nitrido-silicates. III [1] High-Temperature Synthesis, Crystal Structure, and Magnetic Properties of Ce₃[Si₆N₁₁] Pure Ce₃[Si₆N₁₁] was obtained as transparent yellow crystals by reaction of metallic cerium with silicon diimide (Ce:Si = 1:2) under nitrogen atmosphere in a specially developed high-frequency furnace at 1660°C. Ce₃[Si₆N₁₁] (P4bm, a = 1013.7(3), c = 483.9(5) pm, Z = 2, R = 0.034, wR = 0.024) contains Ce³⁺ ions as well as a three-dimensional covalent anionic network structure of corner-sharing SiN₄ tetrahedra. Measurements of the magnetic susceptibility gave no indications for magnetic ordering phenomena in the temperature range between 2 and 300 K. Above 100 K pure Curie-Weiss behaviour (μ_eff = 2,10 μ_B, determined at room temperature) was observed.     

The Binary Silicides Eu5Si3 and Yb3Si5 – Synthesis,Crystal Structure,and Chemical Bonding

The binary silicides Eu₅Si₃ and Yb₃Si₅ were prepared from the elements in sealed tantalum tubes and their crystal structures were determined from single crystal X-ray data: I4/mcm, a = 791.88(7) pm, c = 1532.2(2) pm, Z = 4, wR2 = 0.0545, 600 F² values, 16 variables for Eu₅Si₃ (Cr₅B₃-type) and P62m, a = 650.8(2) pm, c = 409.2(1) pm, Z = 1, wR2 = 0.0427, 375 F² values, 12 variables for Yb₃Si₅ (Th₃Pd₅ type). The new silicide Eu₅Si₃ contains isolated silicon atoms and silicon pairs with a Si–Si distance of 242.4 pm. This silicide may be described as a Zintl phase with the formula [5 Eu²⁺]¹⁰⁺[Si]^4–[Si₂]^6–. The silicon atoms in Yb₃Si₅ form a two-dimensional planar network with two-connected and three-connected silicon atoms. According to the Zintl-Klemm concept the formula of homogeneous mixed-valent Yb₃Si₅ may to a first approximation be written as [3 Yb]⁸⁺[2 Si^–]^2–[3 Si^2–]^6–. Magnetic susceptibility investigations of Eu₅Si₃ show Curie-Weiss behaviour above 100 K with a magnetic moment of 7.85(5) μ_B which is close to the free ion value of 7.94 μ_B for Eu²⁺. Chemical bonding in Eu₅Si₃ and Yb₃Si₅ was investigated by semi-empirical band structure calculations using an extended Hückel hamiltonian. The strongest bonding interactions are found for the Si–Si contacts followed by Eu–Si and Yb–Si, respectively. The main bonding characteristics in Eu₅Si₃ are antibonding Si1₂-π* and bonding Eu–Si1 states at the Fermi level. The same holds true for the silicon polyanion in Yb₃Si₅.     

Synthesis and Luminescence Properties of Amber Emitting La7Sr[Si10N19O3] : Eu2+ and Syntheses of the Substitutional Variants RE8-xAEx[Si10N20-xO2+x] : Eu2+ with RE=La,Ce; AE=Ca,Sr, Ba; 0≤x≤2

The oxonitridosilicate La₇Sr[Si₁₀N₁₉O₃] : Eu²⁺ and its substitutional variants RE_8-xAE_x[Si₁₀N_20-xO_2+x] : Eu²⁺ with RE=La, Ce; AE=Ca, Sr, Ba and 0≤x≤2 were synthesized starting from REN, SrN/Ca₃N₂/Ba₂N, SiO₂, amorphous Si₃N₄ and Eu₂O₃ as doping agent at 1600 °C in a radiofrequency furnace. The crystal structure of La₇Sr[Si₁₀N₁₉O₃] was solved and refined based on single-crystal X-ray diffraction data. La₇Sr[Si₁₀N₁₉O₃] crystallizes in the orthorhombic space group Pmn2₁ (no. 31). The crystal structures of the isotypic compounds RE_8-xAE_x[Si₁₀N_20-xO_2+x] were confirmed by Rietveld refinements based on powder X-ray diffraction data using the single-crystal data of La₇Sr[Si₁₀N₁₉O₃] as starting point. Crystal structure elucidation reveals a 3D network of vertex sharing SiN₄ and SiN₂(N_1/2-x/4O_1/2+x/4)₂ (0≤x≤2) tetrahedra. When excited with UV to blue light, La₇Sr[Si₁₀N₁₉O₃] : Eu²⁺ shows amber luminescence with λ_em=612 nm and fwhm=84 nm/2194 cm⁻¹, which makes it interesting for application in amber phosphor-converted light emitting diodes.     

(OLi2Ca4)3[ReN4]4, ein Nitridorhenat(VI)‐Oxid

(OLi₂Ca₄)₃[ReN₄]₄, a Nitridorhenate(VI) Oxide Black single crystals of (OLi₂Ca₄)₃[ReN₄]₄ were prepared from the elements (molar ratio Li : Ca : Re = 6 : 1 : 1) by reaction with molecular nitrogen at 900 °C; oxygen content results from a leak in the gas supply. The nitridorhenate(VI)‐oxide is an isotype of (OLi₂Ca₄)₃[MN₄]₄ (M = Mo^VI, W^VI). These compounds are obtained under similar reaction conditions in the presence of small amounts of oxygen containing impurities (Li‐/Ca‐hydroxides). The crystal structure of (OLi₂Ca₄)₃[ReN₄]₄ was determined by single crystal methods (cubic; I43d (# 220); a = 1315.88(9) pm; Z = 4) and can be derived from the Th₃P₄ type structure by hierarchical replacements: Th ≙ (OLi₂Ca₄)⁸⁺‐tetragonal bipyramids and P ≙ [Re^VIN₄]^6–‐tetrahedra.     

Novel Barium Beryllates Ba[Be2N2] and Ba3[Be5O8]: Syntheses,Crystal Structures and Bonding Properties

Ba[Be₂N₂] was prepared as a yellow‐green microcrystalline powder by reaction of Ba₂N with Be₃N₂ under nitrogen atmosphere. The crystal structure Rietfeld refinements (space group I4/mcm, a = 566.46(5) pm, c = 839.42(9) pm, R_int = 4.73 %, R_prof = 9.16 %) reveal the compound to crystallize as an isotype of the nitridoberyllates A[Be₂N₂] (A = Ca, Sr) consisting of planar 4.8² nets of mutually trigonal planar coordinated Be and N species. Averaged magnetic susceptibility values for the anion [(Be₂N₂)^2?] determined from measurements on A[Be₂N₂] with A = Mg, Ca, Ba allow to derive a diamagnetic increment for N^3? χ_dia = (?13±1stat.) · 10^?6emu mol^?1. Colorless Ba₃[Be₅O₈] was first obtained as an oxidation product of Ba[Be₂N₂] in air. The crystal structure was solved and refined from single crystal X‐ray diffaction data (space group Pnma, a = 942.9(1) pm, b = 1163.47(7) pm, c = 742.1(1) pm, R1 = 2.99 %, wR2 = 7.15 %) and contains infinite rods of Be in trigonal planar, tetrahedral and 3 + 1 coordination by O. The crystal structure is discussed in context with other known oxoberyllates. Electronic structure calculations and electron localization function diagrams for both compounds support the classification as nitrido‐ and oxoberyllate, respectively.     

Die kristallstruktur des kaliumtetragermanats K2[Ge4O9]

Zusammenfassung Die Kristallstruktur des Kaliumtetragermanats, K₂[Ge₄O₉], wurde mit Hilfe dreidimensionaler Röntgendaten bestimmt. K₂[Ge₄O₉] kristallisiert trigonal mit der Raumgruppe P033034c1 (Nr. 165) und den Gitterparametern:a=11.84 undc=9.80 Å. Die vorgeschlagene strukturchemische Beziehung zum Wadeit, K₂Zr[Si₃O₉], wird durch die Existenz tetraedrischer [Ge₃O₉]-Ringe, die über [GeO₆]-Oktaeder zu einem dreidimensionalen Gerüst verknüpft sind, bestätigt. Es wurden folgende mittlere Ge–O-Abstände gefunden: 1.762 (Tetraeder) und 1.886 Å (Oktaeder).

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The crystal structure of potassium tetragermanate K₂[Ge₄O₉]

The crystal structure of potassium tetragermanate K₂[Ge₄O₉] has been determined by means of three-dimensional x-ray data. K₂[Ge₄O₉] crystallizes trigonal with space group P033034c1 (No. 165) and lattice parametersa=11.84 andc=9.80 Å. The proposed structural relationship to wadeite K₂Zr[Si₃O₉] is confirmed by the existence of [Ge₃O₉] rings built by tetrahedra, which are linked by [GeO₆] octahedra forming a three-dimensional network. The mean Ge–O distances are found to be: 1.762 (tetrahedra) and 1.886 Å (octahedra).

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Mit 2 Abbildungen

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Herrn Prof. Dr.H. Nowotny in Verehrung gewidmet.