New Method of Analysis of Intermolecular Contacts in the Crystal Structure: π-Complexes

A new method for analysis of intermolecular contacts in the crystal structure based on characteristics of the Voronoi-Dirichlet polyhedra (VDP) is considered using metal π-complexes as examples. The crystal data of the compounds were used to determine the surface area of the VDP faces corresponding to all intermolecular contacts in one π-complex, the total volume of the pyramids with VDP faces as bases and the nuclei of atoms involved in the intermolecular contacts at the vertices, and the total solid angle at which the “intermolecular” VDP faces are seen from the corresponding nuclei of the molecule. A common linear correlation between the enthalpy of sublimation of π-complexes and saturated or unsaturated hydrocarbons and the molecular VDP characteristics was elucidated. On the basis of the results, the enthalpies of sublimation were calculated for some iron π-complexes (for which data on the crystal structure were available) and C₆₀ and C₇₀ fullerenes.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 7, 2005, pp. 495–505.Original Russian Text Copyright © 2005 by Serezhkin, Shevchenko, Serezhkina.     

Study of the laser-initiated chlorination of methyltrichlorogermane

Conclusions The high selectivity of the chlorination of CH₃GeCl₃with the formation of CH₂ClGeCl₃ by the action of a UV laser is independent of the emission wavelength in the range from 193 to 308 run. The quantum yield is not less than 10².Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2167–2170, September, 1988.     

The IrX6 Coordination Polyhedra (X = F,Cl, Br) in Crystal Structures

The Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to perform crystal-chemical analysis of compounds containing [Ir _a X _b ] ^z– complexes (X = F, Cl, or Br). The coordination number of Ir atoms with respect to halogen atoms was found to be 6, irrespective of the oxidation state (III, IV, or V), and the coordination polyhedra formed by Ir were found to be always octahedra. The influence of the site symmetry and the valence state of the Ir atoms on the distortion of the IrX₆ octahedra is considered. It is shown that characteristics of the VDP of Ir atoms can be used for quantitative estimation of the crystal-chemical role of Ir atoms in the halide structures.     

The Coordination Polyhedra IrN n in Crystal Structures

Characteristics of the Voronoi–Dirichlet polyhedra were used to perform the crystal-chemical analysis of compounds containing iridium atoms surrounded by nitrogen atoms. The coordination polyhedra formed by Ir(III) atoms are always octahedra (IrN₆), whereas the Ir(2.5) and Ir(II) atoms occurring only in binuclear clusters form the IrN₄Ir ( is the vacancy) and IrN₅Ir quasi-octahedra. The parameters of the Voronoi–Dirichlet polyhedra allow one to estimate quantitatively the main stereochemical characteristics of iridium atoms, depending on their valence state.     

The OsX n Coordination Polyhedra (X = O,S, Se,Te) in Crystal Structures

The Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to perform a crystal-chemical analysis of compounds whose structures contain Os atoms surrounded by chalcogen atoms. Depending on the valence state, Os atoms bind four to seven X atoms (X = O, S, Se, Te) forming OsX _n coordination polyhedra which can be tetrahedra (n = 4), trigonal bipyramids or square pyramids (n = 5), octahedra (n = 6), or pentagonal bipyramids (n = 7). In some compounds, pairs of OsO₆ octahedra share edges to form Os–Os bonds. The influence of the Os valence state and the nature of the chalcogen atom on the composition and structure of the [Os _a X _b ] groups is discussed. On the basis of analysis of the crystal-structural data from the standpoint of the 18-electron rule, dependences of the Os–O and Os–Os bond orders on the bond lengths are proposed.     

The principle of maximum filling and characteristics of sublattices of hydrogen atoms

The most important characteristics of the Voronoi-Dirichlet polyhedra of 4005928 crystallographically different atoms in sublattices only containing hydrogen atoms were determined in the structures of 151044 inorganic, organoelement, and organic compound crystals. In such sublattices, the Voronoi-Dirichlet polyhedra of H atoms most often had 15 faces, and these faces were most often pentagonal. A comparative analysis of H- and C-sublattices was performed to find that the most important geometric and topological characteristics of H-sublattices were caused by the absence of short-range and local long-range order in the mutual arrangement of hydrogen atoms in the structure of crystals.     

Synthesis and structure of Cs[UO<Subscript>2</Subscript>(SeO<Subscript>4</Subscript>)(OH)] · <Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O (<Emphasis Type="Italic">n</Emphasis> = 1.5 or 1)

The synthesis and single-crystal X-ray diffraction study of Cs[UO₂(SeO₄)(OH)] · 1.5H₂O (I) and Cs[UO₂(SeO₄)(OH)] · H₂O (II) are performed. Compound I crystallizes in the monoclinic crystal system, a = 7.2142(2) Å, b = 14.4942(4) Å, c = 8.9270(3) Å, β = 112.706(1)°, space group P2₁/m, Z = 4, and R = 0.0222. Compound II is monoclinic, a = 8.4549(2) Å, b = 11.5358(3) Å, c = 9.5565(2) Å, β = 113.273(1)°, space group P2₁/c, Z = 4, and R = 0.0219. The main structural units of crystals I and II are [UO₂(SeO₄)(OH)]^? layers which belong to the AT ³ M ² crystal chemical group of uranyl complexes (A = UO ₂ ²⁺ , T ³ = SeO₄ ^2?, and M ² = OH^?). In structure I, johannite-like layers are found. Structure II is a topological isomer of I. The two structures differ in the number of U(VI) atoms bound to the central atom by all bridging ligands.     

Analysis of the conformational polymorph crystal structures by means of molecular Voronoi-Dirichlet polyhedra

The nonvalent interactions in the crystal structures of 16 conformational polymorphs of the C _a H _b N _c O _d S _e composition (a, b, c, d, and e are stoichiometric indices), including 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (“ROY”) (which has seven different modifications), have been analyzed using the characteristics of molecular Voronoi-Dirichlet polyhedra. It is established that a unique combination of implementable types of intra- and intermolecular nonvalent contacts corresponds to each conformational polymorph.     

Features of intermolecular interactions in the crystals of metal acetylacetonates

For 12 acetylacetonates of the composition M(acac) _n (n = 2, 3, or 4) and M(acac)(C₂H₄)₂ (M is a metal) the total area (⁰ S) of the faces of Voronoi-Dirichlet polyhedra (VDP) corresponding to all intermolecular contacts of one molecule in the crystal structure and the total volume of pyramids (⁰ V), whose bases are formed of such faces and the vertices are occupied by the nuclei of atoms participating in intermolecular contacts, are determined. The key features of non-bonded interactions are considered. The existence of a linear dependence of the sublimation enthalpy of acetylacetonates on the ⁰ S or ⁰ V parameters of their molecular VDP is revealed. It is shown that the sublimation enthalpy of Ga(acac)₃ requires the refinement and theoretically should be 124 kJ/mol.     

Crystal structure of {NH2C(NHC6H5)2}3[UO2(C2O4)2(NCS)] · 1.25H2O

Synthesis and X-ray diffraction study of {NH₂C(NHC₆H₅)₂}₃[UO₂(C₂O₄)₂(NCS)] · 1.25H₂O single crystals have been performed. This compound is crystallized in the orthorhombic system, with the unit-cell parameters a = 45.2646(8) Å, b = 57.7359(11) Å, c = 7.9244(3) Å, sp. gr. Fdd2, Z = 16, V = 20 709.6(10) ų, and R = 0.0477. The uranium-containing structural units of the crystals are one-core groups of the [UO₂(C₂O₄)₂(NCS)]^3? composition, belonging to the crystallochemical group AB ₂ ⁰¹ M ¹ (A = UO ₂ ⁺² , B ⁰¹ = C₂O ₄ ^2? , M ¹ = NCS^?) of uranyl complexes. The uranium-containing complexes are connected into a three-dimensional framework owing to the electrostatic interactions with the outer-sphere cations and a system of hydrogen bonds.