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.     

Nitrido-Silicate. I. Hochtemperatur-Synthese und Kristallstruktur von Ca2Si5N8

Nitrido Silicates. I. High Temperature Synthesis and Crystal Structure of Ca₂Si₅N₈ Ca₂Si₅N₈ is obtained by reaction of silicon diimide with metallic calcium under nitrogen atmosphere performed in a specially developed high-frequency furnace at temperatures between 1 500 and 1 600°C. Ca₂Si₅N₈ (Cc, a = 1 435.2(3), b = 561.0(1), c = 968.9(2) pm, β = 112.06(3)°, Z = 4, R = 0.023, wR = 0.018) contains Ca²⁺ ions as well as a three-dimensional covalent network structure of corner-sharing SiN₄ tetrahedra. Two sorts of N occur with molar ratio 1:1 which are bonded to two and three Si, respectively.     

Über den H‐ und A‐Typ von La2[Si2O7]

On the H‐ and A‐Type Structure of La₂[Si₂O₇] By thermal decomposition of La₃F₃[Si₃O₉] at 700 °C in a CsCl flux single crystals of a new form of La₂[Si₂O₇] have been found which is called H type (triclinic, P1; a = 681.13(4), b = 686.64(4), c = 1250.23(8) pm, α = 82.529(7), β = 88.027(6), γ = 88.959(6)°; V_m = 87.223(9) cm³/mol, D_x = 5.113(8) g/cm³, Z = 4) continuing Felsche's nomenclature. It crystallizes isotypically to the triclinic K₂[Cr₂O₇] in a structure closely related to that of A–La₂[Si₂O₇] (tetragonal, P4₁; a = 683.83(7), c = 2473.6(4) pm; V_m = 87.072(9) cm³/mol, D_x = 5.122(8) g/cm³, Z = 8). For comparison, the latter has been refined from single crystal data, too. Both the structures can be described as sequence of layers of each of two crystallographically different [Si₂O₇]^6– anions always built up of two corner‐linked [SiO4] tetrahedra in eclipsed conformation with non‐linear Si–O–Si bridges (∢(Si–O–Si) = 128–132°) piled up in [001] direction and aligned almost parallel to the c axis. They differ only in layer sequence: Whereas the double tetrahedra of the disilicate units are tilted alternating to the left and in view direction ([010]; stacking sequence: AB) in H–La₂[Si₂O₇], after layer B there follow due to the 4₁ screw axis layers with anions tilted to the right and tilted against view direction ([010]; stacking sequence: ABA′B′) in A–La₂[Si₂O₇]. The extremely irregular coordination polyhedra around each of the four crystallographically independent La³⁺ cations in both forms (H and A type) consist of eight to ten oxygen atoms in spacing intervals of 239 to 330 pm. The possibility of more or less ordered intermediate forms will be discussed.     

LiSr2[ReN4] und LiBa2[ReN4] – isotype Nitridorhenate(VII)

LiSr₂[ReN₄] and LiBa₂[ReN₄] – isotypic Nitridorhenates(VII) The quaternary nitridorhenates(VII) LiAE₂[ReN₄] (AE = Sr, Ba) were synthesized by reaction of the metals with molecular nitrogen at 850–900 °C. The plate‐like, nearly colourless crystals were investigated by X‐ray single crystal methods and were identified as isotypic phases: LiSr₂[ReN₄] (LiBa₂[ReN₄]); monoclinic, P2₁/m; a = 614.64(8) pm (651.04(12) pm), b = 585.97(6) pm (b = 598.86(9) pm), c = 689.70(17) pm (737.43(5) pm), β = 106.375(4)° (108.535(2)°); Z = 2. Crystals of the strontium compound were systematically twinned along [001]. In the crystal structures of the quaternary compounds the alkaline earth‐ and nitride‐ ions are arranged in the motif of the InNi₂‐type structure. Strontium and barium are in a trigonal prismatic coordination by nitrogen (Sr–N: 261.0(7)–284.3(4) pm; Ba–N: 278.0(7)–303.0(6) pm). One half of the tetrahedral voids within the partial structure formed by stacking of trigonal prismatic rod layers is occupied by rhenium (formation of [Re^VIIN₄]^5–‐tetrahedra; Re–N: 181.0(6)–184.5(8) pm), lithium takes the positions of the remaining tetrahedral sites (Li–N: 2 × 198(1) pm, 224(2) pm and 228(2) pm for the strontium phase). In the barium compound the lithium positions show a larger shift from the tetrahedral centres towards a tetrahedral plane (Li–N: 2 × 195(1) pm, 213(2) pm and 304(2) pm).     

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.     

The Crystal Structures of Two No–Metal Tricyanomelaminates: Diammonium Tricyanomelaminate Dihydrate [NH4]2[C6N9H] · 2 H2O and Dimelaminium Tricyanomelaminate Melamine Dihydrate [C3N6H7]2[C6N9H] · C3N6H6 · 2 H2O

Diammonium tricyanomelaminate dihydrate [NH₄]₂[C₆N₉H] · 2 H₂O ( 1 ) and dimelaminium tricyanomelaminate melamine dihydrate [C₃N₆H₇]₂[C₆N₉H] · C₃N₆H₆ · 2 H₂O ( 2 ) were obtained by metathesis reactions from Na₃[C₆N₉] in aqueous solution and characterized by single‐crystal X‐ray diffraction and ¹⁵N solid‐state NMR spectroscopy ( 1 ). Both salts contain mono‐protonated tricyanomelaminate (TCM) anions and crystallize as dihydrates. Considering charge balance requirements, the crystal structure of 1 (C2/c, a = 3181.8(6) pm, b = 360.01(7) pm, c = 2190.4(4) pm, β = 112.39(3)°, V = 2319.9(8) 10⁶ · pm³) can best be described by assuming a random distribution of an ammonium ion – crystal water pair over two energetically similar sites. Apart from two melaminium cations, 2 (P2₁/c, a = 674.7(5) pm, b = 1123.6(5) pm, c = 3400.2(5) pm, β = 95.398(5), V = 2566(2) 10⁶ · pm³) contains one neutral melamine per formula unit acting as an additional “solvent” molecule and yielding a donor‐acceptor type of π–stacking interaction.     

Synthesis and Structure of Ba[ZrN2] and Ba2[NbN3]

Ba₃N₂ reacts at 950°C under pure N₂ with Zr to yield dark red, air-sensitive Ba[ZrN₂]. This new compound crystallizes in the tetragonal space group P4/nmm with a = 416.10(2), c = 839.2(1) pm and Z = 2. The crystal structure was solved and refined using X-ray and neutron powder diffraction data. In the nitrido zirconate [ZrN₂]^2? the Zr atoms exhibit a square-pyramidal coordination by five N atoms at distances of 201(3) and 220.2(2) pm. The pyramids share all the edges in the basal plane to form layers parallel to (001) with their apices alternately pointing up and down. The Ba²⁺ cations are integrated into these layers at the levels of the pyramidal apices. The structure can be interpreted as a stuffed PbFCl type. Ba₂[NbN₃] is formed by the reaction of Ba₃N₂ and NbN or of Ba and Nb at 1 000°C under N₂. Isostructural to Ba₂[TaN₃] it crystallizes in the monoclinic space group C2/c with a = 613.2(3), b = 1 176.8(3), c = 1 322.9(4) pm, β = 91.65(2)°, Z = 8. The nitrido niobate anions form chains of corner sharing NbN₄ tetrahedra with distances Nb? N between 188(1) and 199.9(9) pm.     

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.     

Li4Sr2[Cr2N6]: Ein Hexanitridodichromat(V)

Li₄Sr₂[Cr₂N₆]: A Hexanitridodichromate(V) The quaternary hexanitridodichromate(V) Li₄Sr₂[Cr₂N₆] was obtained by reaction of the metals with flowing nitrogen at 900 °C as black‐shining crystals with a platy habit. The crystal structure was determined by X‐ray single crystal methods (orthorhombic, Pbca; a = 914.0 pm, b = 735.4 pm, c = 1053.6 pm; Z = 4). The compound contains isolated complex anions [Cr₂N₆]^8— consisting of two tetrahedra CrN₄ sharing a common edge. The distance Cr—Cr in the complex anion is 249.7 pm. The analysis of the Electron Localization Function (ELF) indicates bonding interactions Cr—Cr. Strontium is in a sixfold (distorted octahedral), Lithium in a distorted tetrahedral ([3+1]) coordination by nitrogen. According to measurements of the magnetic susceptibility the compound is diamagnetic.     

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.     

La2Si2O7 im I—Typ: Gemäß La6[Si4O13][SiO4]2 kein echtes Lanthandisilicat

I‐Type La₂Si₂O₇: According to La₆[Si₄O₁₃][SiO₄]₂ not a Real Lanthanum Disilicate In attempts to synthesize lanthanum telluride silicate La₂Te[SiO₄] (from La, TeO₂, SiO₂ and CsCl, molar ratio: 1 : 1: 1 : 20, 950 °C, 7 d) or fluoride‐rich lanthanum fluoride silicates (from LaF₃, La₂O₃, SiO₂ and CsCl, molar ratio: 5 : 2 : 3 : 17, 700 °C, 7 d) in evacuated silica tubes, colourless lath‐shaped single crystals of hitherto unknown I‐type La₂Si₂O₇ (monoclinic, P2₁/c; a = 726.14(5), b = 2353.2(2), c = 1013.11(8) pm, β = 90.159(7)°) were found in the CsCl‐flux melts. Nevertheless, this new modification of lanthanum disilicate does not contain any discrete disilicate groups [Si₂O₇]^6‐ but formally three of them are dismutated into one catena‐tetrasilicate ([Si₄O₁₃]^10‐ unit of four vertex‐linked [SiO₄]^4‐ tetrahedra) and two ortho‐silicate anions (isolated [SiO₄]^4‐ tetrahedra) according to La₆[Si₄O₁₃][SiO₄]₂. This compound can be described as built up of alternating layers of these [SiO₄]^4‐ and the horseshoe‐shaped [Si₄O₁₃]^10‐ anions along [010]. Between and within the layers the high‐coordinated La ³⁺ cations (CN = 9 ‐ 11) are localized. The close structural relationship to the borosilicates M₃[BSiO₆][SiO₄](M = Ce ‐ Eu) is discussed and structural comparisons with other catena‐tetrasilicates are presented.     

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.     

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.     

Synthesis,Crystal Structures,and Vibrational Spectra of Novel Azidopalladates of the Alkali Metals Cs2[Pd(N3)4] and Rb2[Pd(N3)4]·2/3H2O

The transparent dark orange compounds Cs₂[Pd(N₃)₄] and Rb₂[Pd(N₃)₄]·²/₃H₂O are synthesized by reaction of the respective binary alkali metal azides with K₂PdCl₄ in aqueous solutions. According to single‐crystal X‐ray diffraction investigations, the novel ternary azidopalladates(II) crystallize in the monoclinic space group P2₁/c (no. 14) with a = 705.7(2) pm, b = 717.3(2) pm, c = 1125.2(5) pm, β = 104.58(2)°, mP30 for Cs₂[Pd(N₃)₄] and a = 1041.4(1) pm, b = 1292.9(2) pm, c = 1198.7(1) pm, β = 91.93(1)°, mP102 for Rb₂[Pd(N₃)₄]·²/₃H₂O, respectively. Predominant structural features of both compounds are discrete [Pd^II(N₃)₄]^2– anions with palladium in a planar coordination by nitrogen, but differing in point group symmetries., The vibrational spectra of the compounds are analyzed based on the idealized point group C_4h of the spectroscopically relevant unit, [Pd(N₃)₄]^2– taking into account the site symmetry splitting due to the symmetry reduction in the solid phase.     

Dimers and Chains of Hydrogen bonded [HS2O7]– Anions in the Crystal Structures of M[HS2O7] (M = K, [NH4], [NO], Rb,Cs)

The reactions of KCl, [NH₄]₂[SO₄], Rb₂[CO₃], and Cs₂[CO₃] with fuming sulfuric acid (65 % SO₃) yielded colorless and moisture sensitive crystals of K[HS₂O₇] (monoclinic, P2₁/c (no. 14), Z = 4, a = 716.67(3) pm, b = 1043.57(4) pm, c = 828.78(3) pm, β = 107.884(1)°, V = 589.89(4) × 10⁶ pm³), [NH₄][HS₂O₇] (monoclinic, P2₁/c (no. 14), Z = 4, a = 729.29(1) pm, b = 1079.73(1) pm, c = 843.26(1) pm, β = 106.397(1)°, V = 637.01(1) × 10⁶ pm³), Rb[HS₂O₇] (monoclinic, P2₁/c (no. 14), Z = 4, a = 724.49(2) pm, b = 1073.19(3) pm, c = 852.01(3) pm, β = 106.534(1)°, V = 635.06(3) × 10⁶ pm³), and Cs[HS₂O₇] (triclinic, P$\bar{1}$ (no. 2), Z = 2, a = 537.61(3) pm, b = 784.71(4) pm, c = 867.93(4) pm, α = 94.214(2)°, β = 103.138(2)°, γ = 105.814(2)°, V = 339.47(3) × 10⁶ pm³). Colorless crystals of [NO][HS₂O₇] (monoclinic, P2₁/c (no. 14), Z = 4, a = 739.90(4) pm, b = 1048.00(5) pm, c = 830.97(4) pm, β = 106.985(2)°, V = 106.985(2) × 10⁶ pm³) were obtained as a side product from the reaction of [NH₄]₂[Rh(NO₂)₄] with oleum (65 % SO₃) in the ionic liquid [BMIm][OTf]. The crystal structures of K[HS₂O₇], [NH₄][HS₂O₇], [NO][HS₂O₇], and Rb[HS₂O₇] show the [HS₂O₇]^– ions linked into dimers by strong hydrogen bonds. Contrastingly, in the crystal structure of Cs[HS₂O₇] the [HS₂O₇]^– ions are connected to infinite chains. Raman spectra were recorded for M[HS₂O₇] (M = K, Rb, Cs).     

Synthese und Kristallstrukturen von (2‐Methylpyridinium)3[TbCl6] und (2‐Methylpyridinium)2[TbCl5(1‐Butanol)]

Preparation and Structure of (2‐Methylpyridinium)₃[TbCl₆] and (2‐Methylpyridinium)₂[TbCl₅(1‐Butanol)] The complex chlorides (2‐Methylpyridinium)₃[TbCl₆] (1) and (2‐Methylpyridinium)₂[TbCl₅(1‐Butanol)] (2) have been prepared for the first time. The crystal structures have been determinated from single crystal X‐ray diffraction data. 1 crystallizes in the monoclinic space group C2/c (Z = 8) with a = 3241,2(5) pm, b = 897,41(9) pm, c = 1774,2(2) pm and β = 97,83(2)°, 2 in the monoclinic space group P2₁/n (Z = 4) with a = 1372,96(16) pm, b = 997,57(9) pm, c = 1820,5(2) pm and β = 108,75(1)°. The structures contain isolated octahedral building units [TbCl₆]^3– and [TbCl₅(1‐Butanol)]^2–, respectively.     

Hydrogendiazid Synthese und Kristallstruktur von PPh4[N3HN3]

Hydrogen Diazide – Synthesis and Crystal Structure of PPh₄[N₃HN₃] PPh₄[N₃HN₃] has been prepared from PPh₄N₃ and Me₃SiN₃ by the reaction with water or ethanol forming colourless nonexplosive crystal needles, which were characterized by IR spectroscopy and by a crystal structure determination. Space group C2/c, Z = 12, lattice dimensions at –70 °C: a = 3782.4(3), b = 727.8(2), c = 2512.4(2) pm, β = 110.13(1)°, R = 0.0841. The [N₃HN₃]^– ion is characterized by an asymmetric N–H…N hydrogen bridge with a NN distance of 272(1) pm.     

Synthesis,Crystal Structure and Properties of Rubidium Dihydrogentricyanomelaminate Semihydrate Rb[H2C6N9] · 1/2 H2O

Rubidium dihydrogentricyanomelaminate semihydrate Rb[H₂C₆N₉] · ¹/₂ H₂O was obtained as colorless rod‐like single crystals from a solution of Rb₃[C₆N₉] · H₂O and 0.1 M HCl after water evaporation at room temperature. According to the X‐ray single‐crystal structure determination (Rb[H₂C₆N₉] · ¹/₂ H₂O: C2/c (no. 15), a = 2007.4(3) pm, b = 512.2(1) pm, c = 2168.0(4) pm, β = 111.66(2)°, Z = 8, R1 = 0.059, 2391 independent reflections, 159 parameters) Rb⁺ and cyclic planar [H₂C₆N₉]^— ions as well as hydrate water molecules occur in the crystal. Rb[H₂C₆N₉] · ¹/₂ H₂O was investigated by FTIR and Raman spectroscopy, TG measurements and temperature‐dependent X‐ray powder diffraction. According to the thermoanalytic investigations, dehydration of Rb[H₂C₆N₉] · ¹/₂ H₂O starts above 60 °C and is finished below 250 °C.     

Synthesis and crystal structures of Cd[AlCl4]2 and Cd2[AlCl4]2

Colorless single crystals of Cd[AlCl₄]₂ grow from the melt of CdCl₂ and AlCl₃ upon slow cooling from 250°C. The crystal structure [monoclinic, P1a1, Z = 2, a = 1288.7(2), b = 660.2(1), c = 705.1(1) pm, β = 92.89(1)º] may be derived from hexagonally closest packed layers of Cl^?. Octahedral and tetrahedral holes are filled with Cd²⁺ and Al³⁺ in a 1:2 ratio between all layers stacked in the [104] direction. Cd[GaCl₄]₂ and Cd[AlBr₄]₂ are isotypic. Reduction of Cd[AlCl₄]₂ with excess cadmium shot and slow cooling from 350°C yields plate-like very moisture-sensitive, colorless single crystals of Cd₂[AlCl₄]₂. The crystal structure [triclinic, C1 , Z = 2, a = 655.47(3), b = 1135.26(1), c = 935.23(6) pm, α = 89.70(2)º, β = 103.61(1)º, γ = 90.455(1)º] is built from slabs stacked in the [100] direction consisting of ethane-like [Cd₂Cl₆] units with a Cd? Cd distance of 256.1 pm sharing common vertices with [AlCl₄] tetrahedra.