M. Yu. Antipin

Tris(triphenylphosphinegold)oxonium salts

Abstract The oxonium salts (Ph3PAu)3O+X- where X-  BF4-, CF3COO-, MnO4- have been prepared. These salts are formed from coordinatively unsaturated Ph3PAu+ cations in alkaline or acid media. An X-ray study of (Ph3PAu)3O+BF4- indicates that the oxonium ions are dimeric in the crystalline form. The fragment (Ph3PAu)3O has a pyramidal structure: the oxygen atom is outside the Au3 plane.

Vinylidene complexes of transition metals ☆: III. Derivatives of cyclopentadienyltricarbonyl rhenium with phenylvinylidene ligands. Crystal and molecular structure of Cp(CO)2Re[CC(Ph)C(Ph)CH2]Re(CO)2Cp

Abstract The novel complexes CpRe(CCHPh)(CO) 2 and Cp 2 Re 2 (μ-CCHPh)(CO) 4 containing a terminal and a bridging phenylvinylidene ligand respectively and the binuclear complex Cp(CO) 2 Re[CC(Ph)C(Ph)CH 2 ]Re(CO) 2 Cp were obtained in the reaction of CpRe(CO) 3 with PhCCH. According to an X-ray study of the latter complex the unusual bridging ligand is η 1 -bonded to one Re atom and η 2 -bonded to the other.

Carboranes: chemical concepts derived from the AIM study of the experimental and theoretical electron density distribution functions

On the basis of high-resolution X-ray diffraction studies as well as quantum-chemical calculations of five carborane derivatives the peculiarities of electron density distribution functions have been analyzed. The data obtained permitted a deeper insight into the nature of unusual properties of the C-C bond in o-carborane and investigating intermolecular H ... H interactions in crystal. It was shown that such an approach allows estimating the values of lattice energy for the crystals of carboranes.

Crystal and molecular structures of bis(1,3-di-tert-butylcyclopentadienyl)cerium chloride and borohydride. First example of the bridging tetradentate BH4-group with two μ3-hydrogens: μ : η4-[(μ3-H)2B(μ2-H)2]

Abstract Interaction between CeCl 3 and two equivalents of (C 5 H 3 Bu t 2 ) Na leads to the complex [(η 5 -C 5 H 3 Bu t 2 ) 2 Ce(μ 2 -Cl)] 2 . ( I ). Crystals of 1 are rhombic, a = 13.032(3), b = 24.629(5), c = 17.044(3) A, space group Pbnb , Z = 4, d = 1.630 g cm −3 . Complex I reacts with one equivalent of LiBH 4 to afford {(η 5 -C 5 H 3 Bu t 2 ) 2 Ce[μ: η 4 -(η 3 -H) 2 B(μ 2 -H) 2 ]} 2 ( II ) which is isostructural to I. Two BH 4 groups in complex II are tetradentate and contain two μ 3 - and two μ 2 -bridging hydrogens. Cerium has a 20e environment.

The role of molecular association in the formation of crystals with Z′>1 of some hydroxy-containing compounds

Abstract A convenient simple method is proposed for the crystallochemical analysis of structures containing several molecules in the asymmetric unit of the crystal cell (Z′>1). The basic statistical data on the structures with Z′>1 found in the Cambridge structural database, and the role of molecular association in occurrence of pseudosymmetry in organic crystals are discussed.

The structure of dibromoagelaspongin - a novel bromine-containing guanidine derivative from the marine sponge agelas sp.

Abstract A novel bromine-containing guanidine derivative, dibromoagelaspongin hydrochloride 1 , has been isolated from the marine sponge Agelas sp . The structure of this compound has been determined by UV-, IR-, NMR-spectral and X-ray analysis.

Distortion of “tetrahedral” C3v coordination in the R3CO moiety due to the reduction of molecular symmetry: X-ray,. conformational, and quantum-chemical study

Abstract Distortions of the ideal configuration of the R3AX moiety in R3AXR′ type molecules are established by X-ray diffraction (R, R′ = organic substituent, A  element of maingroups IV or V of the periodic table, X = non-linearly coordinated O, S or N atom): the RAX bond angle (φ) in the transoid RAXR′ moiety is essentially smaller than the tetrahedral value of 109.5°. Decrease of the φ angle in Me3COME (I) and Me3COOCMe3 (II) molecules was obtained in molecular mechanic (φI = 103.9°, φΠ = 106.5°) and CNDO/2 (φI = 105.2°, φΠ = 104.3°) calculations and substantiated by the low-temperature X-ray study. The effect of symmetric coordination distortion has evidently, an electronic nature and is also observed in planar trigonal, trigonal-bipyramidal and octahedral environments.

Crystal structure of the electric-fieldinduced ferroelectric phase of NaNbO3

The structure of electric-field-induced ferroelectric phase of NaNbO3 has been studied by means of X-ray diffraction method. Crystal cell is orthorhombic (P21 ma) with parameters: a = 5.569. b = 7.790, c = 5.518 A, V = 239.38 A3, Z = 4. Field-induced phase transition mainly results in reversal of atomic shift directions relative to the cubic perovskite atomic positions in one half of initial orthorhombic cell. Increasing of NbO6 octahedra tilts and additional displacements of some oxygen atoms are accounted for electric field effect.

The isolation and x-ray crystal structure of Δ1,7 2,2,6,6-tetramethyl-4-thia-8,8-dimethyl-8-germabicyclo[5.1.0]octene; The first representative of germirenes

The first representative of germirenes, Δ1,7 2,2,6,6-tetramethyl-4-thia-8,8-dimethyl-8-germabicyclo[5.1.0]octene has been isolated and its X-ray crystal and molecular structure have been determined.

The local structure of mixed-ion perovskites

The temperature-dependent Nb K-edge absorption spectra of several mixed-ion Pb-containing perovskite compounds were analysed to determine the Nb displacement and to trace its changes through the phase transitions. Both extended x-ray absorption fine structure (EXAFS) and the pre-edge region of the spectra were involved in the analysis. The results show that, in the compounds studied, Nb occupies an off-centre position with symmetry lower than that implied by macroscopic symmetry. The magnitude and direction of the Nb off-centre displacement do not display any noticeable temperature change and are not affected by the change in macroscopic symmetry. The Nb–O distribution and its temperature evolution do not show any distinct dependence on the degree of compositional ordering and properties of the samples.