Crystal structure of the synthetic analog of grechishchevite and Hg-X (X = S,Se, Te) bond topology in mercury chalcogen halides

This paper analyzes the structural data available for the synthetic analog of the mineral grechishchevite Hg₃S₂Br_1.00Cl_0.50I_0.50. The crystal structure of the synthetic mineral is refined. For chalcogen halides Hg₃X₂Hal₂ (X = S, Se, Te; Hal = Cl, Br, I), the paper presents an inventory of infinite and isolated ribbons, layers, and frameworks of covalently bonded Hg-X radicals growing into the pseudocubic matrix of halogen atoms.Original Russian Text Copyright © 2004 by N. V. Pervukhina, S. V. Borisov, S. A. Magarill, D. Yu. Naumov, V. I. Vasiliev, and B. G. NenashevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 462–470, May–June, 2004.     

Synthesis and Physicochemical Study of Iron(II), Cobalt(II), Nickel(II), and Copper(II) Complexes with 4-(2-Pyridyl)-1,2,4-Triazole

New complexes of iron(II), cobalt(II), and nickel(II) with 4-(2-pyridyl)-1,2,4-triazole (PyTrz), [Fe₃(PyTrz)₈(H₂O)₄]A₆ (A = NO₃ ^-, ClO₄ ^-, Br^-) and [M₃(PyTrz)₈(H₂O)₄](NO₃)₆ (M = Co, Ni), were synthesized and studied by X-ray diffraction, magnetochemical method, and electronic and IR spectroscopy. The complex [Fe₃(PyTrz)₈(H₂O)₄](NO₃)₆) was also studied by adiabatic calorimetry. The Fe(II), Co(II), and Ni(II) nitrate complexes were shown to be isostructural to the previously synthesized linear trinuclear [Cu₃(PyTrz)₈H₂O)₄](NO₃)₆ complex. In all compounds, antiferromagnetic exchange interactions between M²⁺ ions were detected. The complex [Fe₃(PyTrz)₈(H₂O)₄](NO₃)₆ undergoes the ¹ A ₁ ⁵ T ₂ spin transition.     

Structural chemistry of mercury chalcohalides. III. Crystal structure of Hg<Subscript>3</Subscript>S<Subscript>2</Subscript>Cl<Subscript>1.5</Subscript>Br<Subscript>0.5</Subscript> polymorphs

Single crystals of two new mercury thiohalides of the composition Hg₃S₂Cl_{2? x}Br_x(x = 0.5) have been grown from gas phase and studied by X-ray crystallography. Structure refinement for monoclinic (I) and cubic (II) phases (I: a = 16.841(2) Å, b = 9.128(2) Å, c = 9.435(4) Å; β = 90.080(10)°, V = 1450.3(7) ų, space group _C2/_{m, Z} = 8, _R = 0.0528; II: a = 18.006(2) Å, V = 5837.8(11) ų, space group \(Pm\bar 3n\), Z = 32, R = 0.0503) clearly shows that they are polymorphs of the same composition Hg₃S₂Cl_1.5Br_0.5. The monoclinic modification I is similar to the synthetic phases γ-Hg₃S₂Cl₂, β-Hg₃S₂Br₂, Hg₃Se₂Br₂ and to the analogue of radtkeite mineral, Hg₃S₂ClI. The modification II is isostructural to the synthetic β-Hg₃S₂Cl₂. In both structures, each S atom coordinates three Hg atoms with the formation of pyramidal SHg₃ units (Hg-S 2.37–2.48 Å; HgSHg 93.1–97.5 ). The SHg₃ units are linked through Hg vertices into corrugated layers [Hg₁₂S₈]_∞∞ (I) and isolated cubic groups [Hg₁₂S₈] (II). Similarly to other mercury chalcohalides, the crystal structures are basically determined by the halogen atoms which form a cubic sublattice incorporating the Hg-S moieties.     

Crystal structure,infrared and raman spectra of tripotassium trisaccha-rinate dihydrate,K<Subscript>3</Subscript>(C<Subscript>7</Subscript>H<Subscript>4</Subscript>NO<Subscript>3</Subscript>S)<Subscript>3</Subscript>·2H<Subscript>2</Subscript>O

The crystal structure of tripotassium trisaccharinate dihydrate, K₃(C₇H₄NO₃S)₃·2H₂O, is triclic, space group\(P \bar 1, Z = 2\). It consists of three crystallographically independent potassium and saccharinato ions as well as two structurally different water molecules. Potassium coordination polyhedra are irregular, with K1 and K3 six-coordinated and the third one K2 seven-coordinated. The K?O distances range from 2.652(9) to 3.100(2) Å(mean: 2.790 Å) whereas the K?N distance is 3.025(3) Å. The water molecules W2 is disordered over three positions with occupancies of approximately 0.6, 0.2 and 0.2. The hydrogen atom (H1W1) of the ordered water molecule (O1W) is hydrogen bonded to the sulfonyl oxygen atom (O11) (R(O...O)=2.976(3) Å), whereas the other hydrogen atom (H2W1) is bifurcated to the carbonyl oxygen atom (O13) (R(O...O)=2.851(3) Å) and the disordered water molecules (O23W) (R(O...O)=3.067(12) Å). The carbonyl oxygens (O13, O23 and O33) and one of the disordered water molecules (O22W) are involved in C?H...O hydrogen bonds (R(C?H...O)=3.027(4)–3.304(9) Å). Structural characteristics of the studied compound are compared with the analogous trisodium trisaccharinate dihydrate and dipotassium sodium trisaccharinate monohydrate. Infrared and Raman spectra of the title compound have been analyzed in relation to the structure, and compared with the spectra of trisodium trisaccharinate dihydrate.     

23-Electron Re6 metal clusters: syntheses and crystal structures of (Ph4P)3[Re6S8(CN)6], (Ph4P)2(H)[Re6Se8(CN)6]·8H2O,and (Et4N)2(H)[Re6Te8(CN)6]·2H2O

The cluster anions [Re₆X₈(CN)₆]^34– (X = S, Se, or Te) containing 23 cluster valence electrons in the Re₆ octahedron were synthesized and isolated as salts with organic cations. The crystal structures of the (Ph₄P)₃[Re₆S₈(CN)₆], (Ph₄P)₂(H)[Re₆Se₈(CN)₆]·8H₂O, and (Et₄N)₂(H)[Re₆Te₈(CN)₆]·2H₂O clusters were solved by X-ray diffraction analysis. Removal of one electron has virtually no effect on the geometry and interatomic distances in the cluster anion but leads to a substantial change in the electronic spectrum and to an increase in stretching vibration frequencies _CN compared to those of the [Re₆X₈(CN)₆]^4– anions.     

ESR study of nitro-substituted iminoxyl radicals

Iminoxyl radicals involved in the homolytic oxidation of nitrolic acids, with the general formula (NO₂)RC=NO^., have been detected by means of ESR. In the presence of a strong acid, the ESR spectra of the radical (NO₂)₂C=NO^. exhibits alternation of the line widths, owing to syn-anti isomerization.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1513–1516, July, 1991.     

Synthesis and structure of (bis(3,5-dimethyl-1<Emphasis Type="Italic">H</Emphasis>-pyrazol-1-yl)methane)diiodocobalt(II)

A cobalt(II) iodide complex with bis(3,5-dimethyl-1H-pyrazol-1-yl)methane (L) CoLI₂ has been synthesized, and its single crystals have been obtained. The complex compound was characterized by electron spectroscopy and X-ray diffraction analysis. The compound crystallizes in the monoclinic system (a = 8.4044(4) Å, b = 13.3120(5) Å, c = 14.5824(7) Å; β = 94.7290(10)°; V = 1625.92(13) ų; Z = 4; ρ^calc = 2.112 g/cm³; space group P2₁/m). The structure of the complex is molecular mononuclear. L is a cyclic bidentate ligand; the coordination polyhedron of cobalt is a CoN₂I₂ tetrahedron formed by the nitrogen atoms of the pyrazole fragments L and iodine atoms. The complex has π-π stacking interactions between the pyrazole rings of CoLI₂ molecules, binding the molecules into infinite chains along the b axis.     

Molecular Structure and Conformational Preferences of Trimethyl Phosphorotrithioite,P(SMe)<Subscript>3</Subscript>, Evaluated by Gas-Phase Electron Diffraction and Quantum Chemical Calculations

Free P(SMe)₃ molecule was studied by gas electron diffraction (GED) and by B3PW91/6-311+G* (DFT) and MP2/6-31+G* calculations. Each conformer is characterized by three dihedral angles τ(CSPlp), where lp denotes the direction of the lone electron lone pair on the P atom. DFT calculations indicate that the most stable conformer is an anti,gauche+,gauche- (ag+g-) conformer of C _s symmetry; the next are the ag+g+ (ΔE = 2.5 kJ mol⁻¹), g+g+g+ (ΔE = 5.2 kJ mol⁻¹), and aa+g+ (Δ E = 12.5 kJ mol⁻¹) conformers. The MP2 calculations give the similar order, with the relative energies of 0.3, 4.3, and 10.6 kJ mol⁻¹, respectively. The experimental GED data agree well with the presence of only two conformers: χ(ag+g+) = 80(20)% and χ(ag+g-) = 20(10)%.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005, pp. 742–750.Original Russian Text Copyright © 2005 by Belyakov, Khramov, Baskakova, Naumov.     

Molecular Structure of 1,3,2-Diheterophospholenes in the Gas Phase. Effect of the Nature of Atoms in the Nearest Environment of the Phosphorous Atom on the P-X (X = F,Cl) Bond Length

Molecular parameters of 2-chloro-5-methyl-1,3,2-oxazaphospholene were repeatedly determined invoking nomempirical quantum-chemical calculations. The molecule has a P-envelope conformation with an axial P-Cl bond. Analysis of the molecular structures of 1,3,2-diheterophospholenes, studied experimentally and predicted by quantum-chemical calculations at different levels of theory is performed.     

Synthesis of the aglycone of 26-O-deacetyl pavoninin-5

The aglycone of 26-O-deacetyl pavoninin-5, (25R)-cholest-5-en-3β,15α,26-triol, 5a, was synthesized in 10 steps in 17% overall yield from diosgenin, 3. Removing mercury from the Clemmensen reduction of diosgenin 3, gave a higher yield of (25R)-cholest-5-en-3β,16β,26-triol, 4, by a method, that is also more environmentally friendly. Attempted methods for the transposition of the C-16β hydroxyl to the 15α position are described. A successful method for this transposition via the 15α-hydroxy-16-ketone, 13, using the Barton deoxygenation reaction on the 16-alcohol, 15, is reported.