The Crystal Structures of the Room Temperature and the Low Temperature Phase of Dimethylammonium Trifluoromethanesulfonate

Dimethylammonium trifluoromethanesulfonate 1 was synthesized by reaction of trifluoromethanesulfonic acid with an excess of dimethylamine. A temperature variable synchrotron measurement on the polycrystalline substance reveals that 1 passes through a phase transition below room temperature. The transition occurs in the temperature range of 282–285 K on heating and 272–280 K on cooling as determined by DSC. The room temperature phase crystallizes in space group Cmca (a = 11.031(6) Å, b = 18.466(14) Å, c = 8.173(9) Å, V = 1665(2) ų, Z = 8) and the low temperature phase in space group P 2₁/c (a = 8.8717(18) Å, b = 8.0838(16) Å, c = 10.968(2) Å, β = 92.128(4)°, V = 786.0(3) ų, Z = 4). The structures of both phases were determined by single crystal X‐ray diffraction, but refinement did not yield satisfactory residuals for the low temperature phase because of twinning of the crystal. It was, therefore, independently solved from the synchrotron powder diffraction data using rigid body models of the constituent ions and ab‐initio direct space methods. Both, the CF₃ group and the SO₃ group of the triflate ion, are rotationally disordered around the S–C bond, in the room temperature phase. In the low temperature phase, the triflate ion is well localized. Like in the alkali metal triflates, the triflate ions are arranged in double layers with the hydrophobic trifluoromethyl groups and the sulfonate groups, respectively, pointing towards each other. The dimethylammonium ion is located closer to the sulfonate group with contacts indicating hydrogen bonding. The packing in both phases is of the topological CsCl structure type.     

Crystal Structure and Ionic Conductivity of Cesium Trifluoromethyl Sulfonate,CsSO3CF3

The crystal structures of the room and the high temperature modifications of cesium trifluoromethyl sulfonate were solved from high resolution X‐ray powder diffraction data. At room temperature, α‐CsSO₃CF₃ crystallizes in the monoclinic space group P2₁ with lattice parameters a = 9.7406(2) Å, b = 6.1640(1) Å, c = 5.4798(1) Å, and β = 104.998(1)°; Z = 2. At temperatures above T = 380 K, a second order phase transformation towards a disordered C‐centered orthorhombic phase in space group Cmcm occurs with lattice parameters at T = 492 K of a = 5.5074(3) Å, b = 19.4346(14) Å, and c = 6.2978(4) Å; Z = 4. Within the crystal structures, the triflate anions are arranged in double layers with the apolar CF₃‐groups pointing towards each other. The cesium ions are located between the SO₃‐groups. CsSO₃CF₃ shows a specific ion conductivity ranging from σ = 1.06·10^?8 Scm^?1 at T = 393 K to σ = 5.18·10^?4 Scm^?1 at T = 519 K.     

两个Fe(II)配合物的合成、结构、磁性和穆斯堡尔谱 —— 配合物[Fe(dpq)(Mepy)2(NCS)2]的室温自旋交叉行为

设计制备了两个新的配合物[Fe(dpq)(Mepy)2(NCS)2](1)和[Fe(Medpq)(Mepy)2 (NCS)2](2)。室温下X衍射结果表明配合物（2）为正交晶系,晶胞参数为a = 15.057(3) Å, b = 14.569(3) Å, c = 13.180(3) Å, a = 90.00°, b=90.00°, g = 90.00°。[FeN6] 变型八面体构型中,两个NCS-与其顺式配位,其余四个氮分别来自Medpq和两个Mepy。变温磁化率和穆斯堡尔谱学的研究表明配合物（1）（2）存在自旋交叉,配合物（1）的自旋转换温度为 T1/2 =340K,而配合物（2）在低温条件下的转换是不完全的。     

Structural phase transition,thermal analysis,and spectroscopic studies in an organic–inorganic hybrid crystal: [(CH3)2NH2]2ZnBr4

An organic–inorganic hybrid compound [(CH₃)₂NH₂]₂ZnBr₄ has been prepared at room temperature under the slow evaporation method. Its structure was solved at 150 K using the single-crystal X-ray diffraction method. [(CH₃)₂NH₂]₂ZnBr₄ crystallizes in the monoclinic system – a = 8.5512 (12) Å, b = 11.825 (2) Å, c = 13.499 (2) Å, β = 90.358 (6)°, V = 1365 (4) ų, and Z = 4, space group P2₁/n. In the structure of [(CH₃)₂NH₂]₂ZnBr₄, tetrabromozincate anions are connected to organic cations through N–H⋯ Br hydrogen bonds. Differential scanning calorimetry (DSC) measurements indicate that [(CH₃)₂NH₂]₂ZnBr₄ undergoes four phase transitions at T₁ = 281 K, T₂ = 340 K, T₃ = 377 K, and T₄ = 408 K. Meanwhile, several studies including DSC measurements and variable-temperature structural analyses were performed to reveal the structural phase transition at T = 281 K in [(CH₃)₂NH₂]₂ZnBr₄. Conductivity and dielectric study as a function of temperature (378 < T [K] < 423) and frequency (10⁻¹ < f [Hz] < 10⁶) were investigated. Analysis of equivalent circuit, alternating current conductivity, and dielectric studies confirmed the phase transition at T₄. Conduction takes place by correlated barrier hopping in each phase.     

The Low and High Temperature Crystal Structures of [Mg(H2O)6]XBr3 Double Salts (X = Rb,Cs

The crystal structures of the alkali double salts [Mg(H₂O)₆]XBr₃ (X = Rb⁺, Cs⁺) were analyzed in dependence on temperature from laboratory and synchrotron X‐ray powder diffraction data. At room temperature, both compounds are isostructural to [Mg(H₂O)₆](NH₄)Br₃ (C2/c; Z = 4; a = 9.64128(6) Å, b = 9.86531(5) Å, c = 13.78613(9) Å, β = 90.0875(5)° for [Mg(H₂O)₆]RbBr₃; a = 9.82304(7) Å, b = 9.98043(6) Å, c = 14.0100(1) Å, β = 90.1430(4)° for [Mg(H₂O)₆]CsBr₃). At a temperature of T = 358 K, [Mg(H₂O)₆]RbBr₃ undergoes a reversible phase transition towards a cubic perovskite type of structure with the [Mg(H₂O)₆]²⁺ octahedron in the cuboctahedral cavity exhibiting 4‐fold disorder ( ; a = 6.94198(1) Å at T = 458 K). In case of [Mg(H₂O)₆]CsBr₃ the lattice parameters in dependence on temperature show a distinct kink at T = 340 K, but no symmetry breaking phase transition occurs before decomposition starts. The dominant role of hydrogen bonding with respect to the stability of the crystal structures is discussed.     

Syntheses,Structures, and Polymorphism of β‐Diketonato Complexes – Co(thd)3

Oxidation of Co(thd)₂ dissolved in different solvents has been investigated in air and oxygen atmosphere. In oxygen atmosphere and at the boiling point of the solvents this treatment leads to oxidation of Co^II to Co^III, but also to degradation of some of the thd ligands and formation of a new mixed‐ligand complex. Three pure‐cultivated crystalline Co(thd)₃ phases are reported: 1 (room‐temperature phase), 2 (low‐temperature phase), and 3 (metastable phase) and in addition there exists an amorphous Co(thd)₃ phase ( 4 ) with approximate composition Co(thd)₃·xH(thd); x = 0.06. Reaction of metal(II) oxides (MO, M = Mn, Fe, and Co) with H(thd) under air or O₂ atmosphere is an easy direct route to M(thd)₃ complexes. Structure determinations are reported for Co(thd)₃ ( 1 – 3 ) based on single‐crystal X‐ray diffraction data. Modification 1 crystallizes in space group with a = b = 18.8100(10), c = 18.815(2) Å at 295 K; R(wR2) = 0.180, modification 2 in space group C2/c with a = 28.007(12), b = 18.482(8), c = 21.356(9) Å, β = 97.999(5)° at 100 K; R(wR2) =0.211, and modification 3 in space group Pnma with a = 19.2394(15), b = 18.8795(15), c = 10.7808(8) Å at 100 K; R(wR2) = 0.193. The molecular structures of 1 – 3 all comprise a central Co atom octahedrally co‐ordinated by the ketonato O atoms of three thd ligands. The transformation between modifications 1 and 2 is of a fully reversible second‐order character. Modifications 1 and 3 are, on the other hand, related by a quasi‐reversible cycle. Heat treatment (specifically sublimation) of 1 leads to 3 whereas re‐crystallization or prolonged storage at room temperature is required to regenerate 1 . Co(thd)₃ has sufficient thermal stability to permit sublimation without degradation. The various forms of Co(thd)₃ are all diamagnetic, viz. a confirmation of the Co^III valence state.     

Kristallstruktur,Phasenumwandlung und Kaliumionenleitfähigkeit von Kaliumtrifluormethylsulfonat

Crystal Structure, Phase Transition, and Potassium Ion Conductivity of Potassium Trifluoromethanesulfonate According to the results of temperature dependent powder diffractometry (Guinier‐Simon‐technique) potassium trifluoromethanesulfonate is dimorphic. The phase transition occurs between –63 °C and –45 °C. The low‐temperature modification crystallizes monoclinic with a = 10.300(3) Å, b = 6.052(1) Å, c = 14.710(4) Å, β = 111.83(2)° (–120 °C) and the room‐temperature modification with a = 10.679(5) Å, b = 5.963(2) Å, c = 14.624(5) Å, β = 111.57(3)°, Z = 6, P2₁. According to single crystal structure determination, potassium trifluoromethanesulfonate consists of three different potassium‐oxygen‐coordination polyhedra, linked by sulfur atoms of the trifluoromethanesulfonate groups. This results in a channel structure with all lipophilic trifluoromethane groups pointing into these channels. By means of DSC, the transition temperature and enthalpy have been determined to be –33 °C and 0.93 ± 0.03 kJ/mol, respectively. The enthalpy of melting (237 °C) for potassium trifluoromethanesulfonate is 13.59 kJ/mol, the potassium ionic conductivity is 3.68 · 10^–6 Scm^–1 at 205 °C.     

The Reconstructive Phase Transformation β‐Co2P → α‐Co2P and the Structure of the High‐Temperature Phosphide β‐Co2P

Metallographical and differential thermoanalytical (DTA) investigatitons indicate that the well known phosphide Co₂P (Pearson code oP12, space group Pnma, Co₂Si type) is not stable up to the melting point, T = 1659 K; it is therefore designated as the low‐temperature phase α‐Co₂P. In the temperature range from 1428 to 1659 K, another, high‐temperature phase, designated as β‐Co₂P, exists. X‐ray powder diffraction investigation of liquid quenched alloys in the composition range x_P = 0.25 to 0.335, with x_P as the mole fraction, show that the high‐temperature phase β‐Co₂P is isotypic with Fe₂P (hP9, P 6 2m). For the ideal composition Co₂P, the unit cell parameters are: a = 5.742(2) Å, c = 3.457(5) Å, c/a = 0.621. Among the binary transition metal‐containing phosphides and arsenides isotypic with Fe₂P, β‐Co₂P is the only known high‐temperature phase and it shows (i) the highest axial ratio c/a and (ii) the “smallest” distortion of the hcp substructure formed by the transition metals atoms in the Fe₂P structure type.     

Synthesis and Crystal Structures of Tris-[3, 5-bis(trifluoromethyl)phenyl]arsine Oxide at 293 and 100 K and the Localization of the Trifluoromethyl Groups

Tris[3, 5-bis(trifluoromethyl)phenyl]arsine oxide ( 1 ) was synthesised by oxidation of tris[3, 5-bis(trifluoromethyl)phenyl]arsine with hydrogen peroxide in acetone. At 293 K, it crystallizes in the trigonal space group R3c (a = 20.2947(12) Å, c = 11.2484(13) Å, Z = 6, R₁ = 0.0254). The compound undergoes a phase transition upon cooling, and it crystallizes in the monoclinic space group Cc at 100 K (a = 13.8621(13) Å, b = 18.6537(17) Å, c = 11.2874(10) Å, Z = 4, R₁ = 0.0444). The crystal structures of both phases were determined. The fluorine atoms of the trifluoromethyl groups are strongly disordered at room temperature, which probably indicates a rotational motion in the plane of the fluorine atoms. This motion slows down while lowering the temperature, and the fluorine atoms are localized at 100 K. This point is illustrated by comparison of the experimental electron densities at the CF₃ groups. The packing pattern in both structures consists of parallel columns of ecliptically stacked molecules. The columns are hexagonally arranged.     

Crystal Structures,Dimorphism and Lithium Mobility of Li7MO6 (M = Bi,Ru, Os)

Li₇MO₆ (M = Bi, Ru, Os) have been synthesized by solid state reaction of Li₂O with Bi₂O₃, or MO₂ (M = Ru, Os) and characterized using powder X‐ray diffraction, differential scanning calorimetry, magnetic susceptibility (for M = Ru, Os), ionic conductivity and ⁶Li solid state NMR (for M = Bi) measurements. All three compounds exhibit a temperature induced triclinic – rhombohedral phase transition. Structures of the new low temperature triclinic phases have been refined by the Rietveld method from powder X‐ray data using atomic parameters of Li₇TaO₆ as a starting model ( Li₇BiO₆ : triclinic, , a = 5.5071(1), b = 6.0425(1), c = 5.5231(1) Å, α = 116.912(1), β = 120.867(1), γ = 62.234(1)°, V = 133.96(1) ų, Z = 1, T = 230 K; Li₇RuO₆ : triclinic, , a = 5.3654(1), b = 5.8584(1), c = 5.3496(1) Å, α = 117.182(1), β = 119.117(1), γ = 62.632(1)°, V = 124.43(1) ų, Z = 1, T = 295 K; Li₇OsO₆ : triclinic, , a = 5.3786(1), b = 5.8725(1), c = 5.3591(1) Å, α = 117.193(1), β = 119.277(1), γ = 62.700(1)°, V = 125.15(1) ų, Z = 1, T = 295 K). Upon cooling, Li₇RuO₆ and Li₇OsO₆ undergo a magnetic transition at 12 and 13 K, respectively, from the paramagnetic to the antiferromagnetic state. The higher ionic conductivity of Li₇BiO₆ at T < 300 °C, as compared to Li₇RuO₆ and Li₇OsO₆, can be ascribed to the undergoing of the triclinic – rhombohedral transition at a much lower temperature. At T > 300 °C, the ionic conductivity of all three compounds increases sharply due to the melting of the lithium sublattice; for Li₇RuO₆ and Li₇OsO₆ the latter effect is superimposed by the phase transitions to the rhombohedral modifications.     

Cu3SbS3: Zur Kristallstruktur und Polymorphie

Cu₃SbS₃: Crystal Structure and Polymorphism The hitherto unknown crystal structure of β-Cu₃SbS₃ at room temperature could be determined from a twinned crystal. The compound crystallizes in the monoclinic system, space group P2₁/c (No. 14), with a = 7.808(1), b = 10.233(2) and c = 13.268(2) Å, β = 90.31(1)°, V = 1 060.1(2) ų, Z = 8. An Extended-Hückel-Calculation shows weak bonding interactions between copper atoms which are coordinated trigonal planar. At ?9°C a first order phase transition occurs and the crystals disintegrate. The low-temperature modification (γ) crystallizes in the orthorhombic system with a = 7.884(2), b = 10.219(2) and c = 6.623(2) Å, V = 533.6(2) ų (?100°C). At 121°C a phase transition of higher order is observed. The high-temperature polymorph (α) of Cu₃SbS₃ is orthorhombic again. From high-temperature precession photographs the space groups Pnma (No. 62) or Pna2₁ (No. 33) can be derived. The lattice constants at 200°C are a = 7.828(3), b = 10.276(4) and c = 6.604(3) Å, V = 531.2(2) ų.     

Circumventing the perovskite pattern: Linear ruthenate(V) polyoxoanions in Bi2NaRuO6

Phase pure, coarse crystalline Bi₂NaRuO₆ was synthesized in a hydrothermal approach. It displays a new crystal structure (Pnma (62), a = 12.1408(1) Å, b = 7.49282(6) Å, c = 12.1163(1) Å, Z = 8), which is characterized by a quasi-1D poly-oxoanion composed of (RuO6) octahedra sharing oxygen atoms in trans position. The magnetic response at high temperatures is described by a Curie-Weiss law reflecting strong antiferromagnetic interactions. The obtained effective magnetic moment complies with the d³ configuration for Ru⁵⁺. Below 208 K a weakly ferromagnetic state evolves while no phase transition could be observed in a heat capacity measurement. The compound displays activated electrical conduction. The overall composition and the ionic radii ratios of the constituents encourage to apply elevated hydrostatic pressure in order to realize the title compound in a double perovskite type arrangement, instead of the chain-like structure encountered at ambient conditions.     

Temperature Dependence of the Weak Host-guest Interactions in the p‐tertbutylcalix[4]Arene 1:1 Toluene Complex

Abstract

The temperature dependence of the CH₃… π hostguest interaction in the p‐tertbutylcalix[4]arene 1:1 toluene complex has been investigated by comparison of its known molecular structure at room temperature (RT) with that at 220 K determined by single crystal X-ray diffraction. The diffraction pattern showed a phase transition when the temperature was decreased from 298 to 220 K.

The structure at 220 K could be solved assuming a twin by pseudo-merohedry with a fourfold twin axis [001] relating two monoclinic components with equal volumes of space group P 112/a a = b = 17.899(2), c = 13.827(1) Å, V = 4429.8(8) ų, Z = 2, mol. weight 741.06 a.m.u., D _calc = 1.111 g·cm^?3.

The structure refinement converged to R1 = 0.103 and wR2 = 0.256 for 1655 unique observed data.

The complex exists in two different conformations of the hosts which exhibit two different host-guest structural relationships both indicating that the most relevant differences induced by the low temperature are concerning the host-guest interaction mode.

Particularly unexpected is the different temperature dependence of the CH₃…π interactions between the tert-butyl of the host and the aromatic moiety of the guest with respect to that of the van der Waals interactions. The CH₃…π interactions, which stabilizes the complex at RT, strongly decrease as the temperature decreases.     

Jahn‐Teller‐Ordnung in Mangan(III)‐fluoridsulfaten. II. Phasenübergang und Verzwillingung bei K2[MnF3(SO4)] und 1D Magnetismus in Verbindungen A2[MnF3(SO4)] (A = K,NH4, Rb,Cs)

Jahn‐Teller Ordering in Manganese(III) Fluoride Sulfates. II. Phase Transition and Twinning of K₂[MnF₃(SO₄)] and 1D Magnetism in Compounds A₂[MnF₃(SO₄)] (A = K, NH₄, Rb, Cs) According to single‐crystal X‐ray investigations, K₂[MnF₃(SO₄)] crystallizes at low temperature, like the isostructural Rb, NH₄, and Cs analogues in space group P2₁/c, Z = 4, e.g. at 100 K with a = 7.197, b = 10.704, c = 8.427Å, β = 91.84°. Below about 300 K, the crystals are found to be [001] axis twins. Using a new integration method for area detector records, nearly complete intensity data could be gained allowing for structure refinements of similar quality as for untwinned crystals (e.g. at 100 K: wR₂ = 0.050, R = 0.020 for all reflections). With rising temperature, the monoclinic angle approaches continuously 90°. For an ordering parameter Δβ = β?90° a 2^nd‐order phase transition is observed with an exponent λ = 0.17. At the transition temperature of 280 K resulting from the fit, the monoclinic structure changes – with delay – to orthorhombic with the minimum super‐group Pnca, a = 7.243, b = 10.763, c = 8.457Å, R = 0.024, as found in an early structure determination at room temperature by Edwards 1971. In the chain‐like [MnF₃(SO₄)]^2? anions, manganese(III) is octahedrally coordinated by two trans‐terminal and two trans‐bridging fluorine ligands as well as by the O atoms of two trans‐bridging sulfate ligands. At low temperature, the octahedral elongation by the Jahn‐Teller effect alternates between a F–Mn–F and an O–Mn–O axis (antiferrodistortive ordering). All bridges are asymmetric. From about 320 K on they become symmetric. Due to 2D dynamical Jahn‐Teller effect all octahedra appear compressed. All compounds A₂[MnF₃(SO₄)] show 1D antiferromagnetism. The antiferrodistortive Jahn‐Teller order at low temperatures and the small bridge angles explain the much lower magnetic exchange energies and their inverse relation to the bridge angles as compared with other fluoromanganate(III) chain compounds with the usual ferrodistortive ordering.     

Synthese,Struktur und Phasenumwandlung von Te4[AsF6]2·SO2

Synthesis, Crystal Structure, and Solid State Phase Transition of Te₄[AsF₆]₂·SO₂ The oxidation of tellurium with AsF₅ in liquid SO₂ yields Te₄²⁺[AsF₆^—]₂ which can be crystallized from the solution in form of dark red crystals as the SO₂ solvate. The crystals are very sensitive against air and easily lose SO₂, so handling under SO₂ atmosphere or cooling is required. The crystal structure was determined at ambient temperature, at 153 K, and at 98 K. Above 127 K Te₄[AsF₆]₂·SO₂ crystallizes orthorhombic (Pnma, a = 899.2(1), b = 978.79(6), c = 1871.61(1) pm, V = 1647.13(2)·10⁶pm³ at 297 K, Z = 4). The structure consists of square‐planar Te₄²⁺ ions (Te‐Te 266 pm), octahedral [AsF₆]^— ions and of SO₂ molecules which coordinate the Te₄ rings with their O atoms in bridging positions over the edges of the square. At room temperature one of the two crystallographically independent [AsF₆]^— ions shows rotational disorder which on cooling to 153 K is not completely resolved. At 127 K Te₄[AsF₆]₂·SO₂ undergoes a solid state phase transition into a monoclinic structure (P112₁/a, a = 866.17(8), b = 983.93(5), c = 1869.10(6) pm, γ = 96.36(2)°, V = 1554, 2(2)·10⁶ pm³ at 98 K, Z = 4). All [AsF₆]^— ions are ordered in the low temperature form. Despite a direct supergroup‐subgroup relationship exists between the space groups, the phase transition is of first order with discontinuous changes in the lattice parameters. The phase transition is accompanied by crystal twinning. The main difference between the two structures lies in the different coordination of the Te₄²⁺ ion by O and F atoms of neighbored SO₂ and [AsF₆]^— molecules.     

Structure and some thermodynamic characteristics of the polymorphs of rubidium silicate Rb6Si10O23

The crystal structure of Rb₆Si₁₀O₂₃ at 296 and 773 K is determined using single-crystal X-ray diffraction. At room temperature the crystals are orthorhombic (space group Cm2m, a = 16.280(5) Å, b = 9.380(5) Å, c = 8.060(5) Å, Z = 2). At 698 K, a first-order phase transition occurs to a hexagonal phase (space group $P\bar 6$ , a = 9.475(5) Å, c = 8.200(5) Å, Z = 1). The silicon-oxygen tetrahedral frameworks of both polymorphs have the same topology: 12-membered channels running along axis c are connected through six-membered windows. The enthalpies of polymorphic transition and melting are determined to be 3.9 ± 0.3 and 160 ± 16 kJ/mol, respectively.     

Electrochemical-hydrothermal Synthesis and Structural Characterization of Zn2(OH)VO4

A new zinc vanadate Zn₂(OH)VO₄ has been synthesized by an electrochemical-hydrothermal method and characterized by single crystal X-ray diffraction. The compound crystallizes in the orthorhombic system, space group Pnma, a = 14.645(1) Å, b = 6.0215(5) Å, c = 8.8757(8) Å, V = 782.7(1) ų, Z = 4, measured at 223 K. In the structure, rutile-type [ZnO₆] octahedral chains are interconnected by [VO₄] tetrahedra to form a framework of composition [Zn(OH)VO₄], the voids of which are filled by Zn cations with trigonal bipyramidal and octahedral coordination. The structure is closely related to that of the adamite-type phases and the minerals descloizite PbZn(OH)VO₄ and tsumcorite Pb_0.5Zn(H₂O)AsO₄.     

Synthesis and Characterization of Acetone Hydrazones

1‐Isopropylidene‐2‐methylhydrazine ( 1 ), 1‐isopropylidene‐2‐hydroxyethylhydrazine ( 2 ) and 1‐isopropylidene‐2‐formylhydrazine ( 3 ) were synthesized by reaction of the corresponding hydrazine with an excess of acetone in the presence of a drying agent (anhydrous sodium sulfate or barium oxide). All compounds 1 – 3 were characterized by elemental analysis, coupled gas chromatography‐mass spectrometry (GC–MS), multinuclear NMR spectroscopy (¹H, ¹³C and ¹⁵N) and vibrational spectroscopy (infrared and Raman). Compounds 1 and 2 are liquid at room conditions and their density was measured by means of a picnometer, however, (at room conditions) compound 3 is a solid and its crystal density and structure were determined by low temperature X‐ray diffraction techniques (monoclinic, P2₁/n, Z = 4, a = 5.666(1) Å, b = 6.254(1) Å, c = 15.277(4) Å, β = 91.30(2)°, V = 541.2(2) ų). The structure of hydrazone 3 is discussed in detail and compared to that of monoformylhydrazine. Finally, the (gas phase) structure of compound 3 was optimized using DFT calculations (B3LYP/6‐31+G(d, p)) and its NBO charges are reported.     

VOCl3: Crystallization,crystal structure,and structural relationships: A joint X-ray and 35Cl-NQR investigation

Cooling of VOCl₃ below its melting point (196 K) yields an amorphous phase, which transforms into the crystalline state upon further cooling. The crystallization is accompanied by a remarkable change in color from pale yellow to deep orange. A single crystal has been grown from the amorphous phase. VOCl₃ crystallizes in the orthorhombic system, space group Pnma, with lattice parameters a = 4.963(1), b = 9.140(4), c = 11.221(5)Å at 133 K; Z = 4. The ³⁵Cl-NQR experiments show two signals at approximately 11.4 MHz of intensity 2:1, which implies two different crystallographic sites for chlorine atoms, in agreement with the centrosymmetric space group Pnma. The crystal structure exhibits isolated tetrahedral molecules VOCl₃ lying on a mirror plane and stacked with their VO axis along [100] to form trigonal prismatic columns. A close relationship exists with the structure of AsBr₃, in which the lone pair occupies the position corresponding to the oxygen atoms.