Showing papers by "Andrei V. Churakov published in 2009"

Novel derivatives of hypervalent germanium: synthesis, structure, and stability

Abstract: Syntheses of a series of novel germanium complexes, viz. RN(CH2CH2NC6F5)2GeHal2 (1, R = Me, Hal = Cl; 2, R = Me, Hal = Br; 3, R = PhCH2, Hal = Cl; 4, R = PhCH2, Hal = Br), as well as MeN[CH2(2-C4H3N)]2GeHal2 (5, Hal = Cl; 6, Hal = Br), by the reaction of GeHal4 with dilithium salts of corresponding triamines 7–9 are presented. PhCH2N(CH2CH2NSiMe3)2GeCl2 (10) was prepared analogously from triamine 11. Other approaches to the synthesized compounds were also tested. Unexpected complexes [N(CH2CH2NSiMe3)2Ge(Hal)]2 (12, Hal = Cl; 13, Hal = Br) were obtained by the reaction of GeHal4 with dilithium salt of Me3SiN(CH2CH2NHSiMe3)2 (14). DFT calculations on this reaction were carried out and discussed. Composition and structures of the novel compounds were established by elemental analyses, 1H, 13C, and 19F NMR spectroscopy. The X-ray structural studies of 1–4 and 12 clearly indicated the presence of a transannular interaction N(ax)→Ge for all studied compounds.

Lariat ethers with fluoroaryl side-arms: a study of CF⋯metal cation interaction in the complexes of N-(o-fluoroaryl)azacrown ethers

Abstract: New lariat ethers, N-(o-fluorophenyl)aza-15-crown-5 (F-A15C5) and N,N′-bis(o-fluorophenyl)diaza-18-crown-6 (F2-A218C6), were prepared by the N-arylation of the corresponding azacrown ethers. The interaction of the ligands with metal cations was studied in solution by 1H and 19F NMR (in acetone-d6) and UV spectroscopy (MeOH) confirming the formation of complexes of F2-A218C6 with K+, Na+, Ag+, Ba2+, Pb2+ and of F-A15C5 with Na+ and giving evidence of CF⋯metal cation interaction. Cation binding constants (β, evaluated by UV titration method), demonstrate that F-A15C5 and F2-A218C6 form more stable complexes than their fluorine-free analogs. The effect depends on the nature of the metal cation and is at a maximum for hard, singly charged cations (up to 3 logβ units for K+ complex of F2-A218C6). The X-ray structures of complexes [Pb(F2-A218C6)(H2O)](ClO4)2 (1) and [Ba(F2-A218C6)(ClO4)2] (2) reveal short Pb–F (2.805 A) and Ba–F (2.965 A) contacts. Complex 2 is centrosymmetric (Ci), while complex 1 has C2 symmetry with one-side coordination of o-fluorophenyl groups to Pb2+. This “one-side” coordination mode of Pb2+ is indicative of a partial localization of the Pb2+ lone pair.

Uranyl aquahydroxylaminate complexes

Abstract: Uranylaqua complexes with N-methyl-, N-ethyl-, N-isopropyl-, and N,N-dimethylhydroxylamines were studied. The structure of [UO2{(CH3)2NO}2(H2O)2] was determined by X-ray crystallography. The N, N -dimethylhydroxylaminate ion is coordinated to uranyl through the nitrogen and oxygen atoms with the formation of a three-membered chelate ring.

Conformational rearrangement of 18-crown-6 upon the formation of aquanitratouranyl complexes: The refinement of crystal and molecular structures for [UO2(NO3)2(H2O)2] · 2H2O · 18C6

Abstract: Comparing the geometry of [UO2(NO3)2(H2O)2] · 2H2O · 18C6 (18C6 = C12H24O6) and IR spectroscopic data, we propose correlations between the conformation of an ethylene oxide unit of 18-crown-6 and the conformation-sensitive frequency in the IR spectrum. Spectral conformational analysis verifies the composition of the 18-crown-6 conformer in the [UO2(NO3)2(H2O)2] · 18C6 complex whose structure is known. The distribution character of hydrogen bonds that retain crown ether molecules in aquanitratouranyl complexes is shown to influence the conformational uniformity of ethylene oxide units of the macrocycle.

Specific features of the structure of tungsten(VI) mononuclear six-coordinate oxohalide complexes: A review

Abstract: The specific features revealed in the structure of the mononuclear octahedral oxohalide complexes of tungsten(VI) have been considered. The structural features of tungsten(VI) monooxo and dioxo complexes, as well as pseudodioxo compounds (tungsten(VI) monoxo complexes containing an additional multiply bonded ligand (=Y) of another type), have been analyzed.

Crystal packing in the structures of diethanolamine derivatives.

Abstract: Four distinct hydrogen-bonding topologies were observed in the structures of six diethanol­amine ligands. These compounds are (1R*,2R*)-2-[(2-hydroxy­ethyl)(methyl)amino]-1,2-diphenyl­ethanol, C17H21NO2, (I), 1-[(2S)-2-(hydr­oxy­diphenyl­methyl)­pyrrolidin-1-yl]-2-methyl­propan-2-ol, C21H27NO2, (II), 2-[(2-hydroxy­ethyl)(methyl)amino]-1,1-diphenyl­ethanol, C17H21NO2, (III), 1-{(2-hydr­oxy-2-methyl­propyl)[(1S)-1-phenyl­ethyl]­amino}-2-methyl­propan-2-ol, C16H27NO2, (IV), 1-{[(2R)-2-hydroxy-2-phenyl­ethyl][(1S)-1-phenyl­ethyl]amino}-2-methyl­propan-2-ol, C20H27NO2, (V), and (1R*,2S*)-2-[(2-hydroxy­ethyl)­(methyl)­amino]-1,2-diphenyl­ethanol, C17H21NO2, (VI). In each compound, all `active' hydroxy H atoms are engaged in hydrogen bonding, but the N atoms are not involved in inter­molecular hydrogen bonding. In the structures of (I), (II) and (IV)–(VI), mol­ecules are linked into chains by inter­molecular O—H⋯O inter­actions. These chains are organized in such a way as to hide the hydro­philic groups inside, and so the outer surfaces of the chains are hydro­phobic. The structure of (VI) contains two distinct non-equivalent systems of inter­molecular O—H⋯O hydrogen bonds formed by disordered hydroxy H atoms.

Synthesis, structure, and reactivity of germanium-containing derivatives of substituted diethanolamines

Abstract: The reaction of dialkanolamines RN(CH2CH2O)(CHR’CHR’OH) (R = Me, Ph, PhCH2; R’ = H, Ph) with tetraethoxygermane gives either 2,2-diethoxy-1,3,6,2-dioxazagermocanes RN(CH2CH2O)(CHR’CHR’O)Ge(OEt)2 or 1,7,9,15-tetraoxa-4,12-diaza-8-germaspiro[7.7]pentadecanes [RN(CH2CH2O) (CHR’CHR’O)]2Ge depending on the reactant ratio. The chemical behavior of the obtained compounds in substitution reactions at germanium was studied. The product structure was confirmed by elemental analysis data and 1H, 13C, and 19F NMR spectroscopy. The cyclotrigermanoxane [MeN(CH2CH2O)2GeO]3 was studied by X-ray diffraction.

Synthesis, structure, and quantum-chemical study of tricarbonyl(4-methoxybenzaldehyde)chromium(0)

Abstract: The structure of tricarbonyl(4-methoxybenzaldehyde)chromium(0) was studied by X-ray crystallography. The crystals are orthorhombic, space group P212121, a = 8.040(1) A, b = 10.510(7) A, c = 13.279(4) A, V = 1122.1(8) A3, Z = 4. Quantum-chemical calculations predict that this compound can exist in the gas phase as two stable conformers with almost the same energies. Their mutual transformations are examined using the density functional theory.