Том 60, № 10 (2019)

The paper summarizes the data on discrete cluster compounds of group five transition metals with chalcogen-donor bridging ligands. Preparation methods, structural types, and some physico-chemical properties are considered.

Molecular relaxation processes in potassium perchlorate KClO₄ are studied using Raman spectroscopy. The first-order structural phase transition in crystalline perchlorate KClO₄ is shown to be temperature-extended. The presence of a pretransition region in the studied perchlorate KClO₄ is reported.

VMoNbTeO catalysts show high activity in the reactions of selective oxidation of ethane and propane. Time-resolved X-ray diffraction is used to study structural transformations of a mixed oxide with the composition (TeO)_0.18(Mo_0.7V_0.22Nb_0.08)₂₀O₅₆ and the structure of the active M1 phase upon heating in a hydrogen atmosphere (1% H₂ in helium). It is shown that the structure of the M1 phase is destroyed in the presence of a reducing agent above 480 °C. The process is accompanied by structural distortions, diminishing of the size of crystalline blocks, elimination of tellurium (due to the reduction and sublimation), and the reduction by molybdenum and vanadium cations. As a result, VMoNb oxides with a disordered structure are formed and rapidly crystallized at T > 480 °C into the rutile-type monoclinic oxide (Mo,V,Nb)O₂ with a variable composition. X-ray photoelectron spectroscopy and transmission electron microscopy data confirm heterogeneous compositions of oxides formed by the decomposition of the initial phase. The surface of the formed particles is enriched with vanadium and niobium present in the composition of the oxides with disordered structure.

A scandium(III) tris-(pivaloyltrifluoroacetonate) complex [Sc(ptac)₃] is synthesized, purified, and characterized by the elemental analysis, IR spectroscopy, and the TG/DTA technique. The complex is a highly volatile and low-melting compound that is stable in air and to heat. Slow evaporation of the mother ethanol liquor at room temperature leads to the growth of single crystals of a mixed-ligand complex with an alcohol molecule: [Sc(EtOH)(ptac)₃]. By single crystal X-ray diffraction at a temperature of 150(2) K the [Sc(ptac)₃] and [Sc(EtOH)(ptac)₃] structures are solved. The crystallographic data are: for C₂₄H₃₀F₉O₆Sc space group P-1, a = 9.1565(2) Å, b = 9.6854(3) Å, c = 17.3271(4) Å, β = 79.927(1)°, V = 1465.79(7) ų, Z = 2, d_calc = 1.428 g/cm³, R = 0.041; for C₂₆F₉O₇Sc space group P-1, a = 9.9376(3) Å, b = 13.0243(4) Å, c = 13.2743(4) Å, β = 111.932°, V = 1575.85(8) ų, Z = 2, d_calc = 1.426 g/cm³, R = 0.048. Both structures are composed of neutral molecules; the metal atom coordinates six oxygen atoms of three ligands of β-diketone ([Sc(ptac)₃]) and additionally an oxygen atom of the ethanol molecule ([Sc(EtOH)(ptac)₃]). Tert-butyl and trifluoromethyl substituents in both complexes are oriented so that they create a facial isomer. The Sc-O distances are within 2.07–2.11 Å in [Sc(ptac)₃], and in [Sc(EtOH)(ptac)₃] they are within 2.10–2.24 Å. In the crystals of both compounds, the molecules are linked by only van der Waals interactions, forming a pseudo-layered structure with a hexagonal arrangement inside the layer. Six shortest Sc⋯Sc distances in [Sc(ptac)₃] are within 8.34–10.42 Å. In [Sc(EtOH)(ptac)₃], a distorted hexagonal packing has an average parameter of ~9.5 Å.

Novel volatile complexes of Ni(II), Co(II), Mn(II), Zn(II) with methoxy-substituted β-diketonate ligands L = (CH₃)₂C(OCH₃)-CO-CH-CO-C(CH₃)₃ and L^F = (CH₃)₂C(OCH₃)-CO-CH-CO-CF₃ are obtained. The novel compounds are identified by a complex of techniques, including CHF elemental, mass spectrometric, and NMR spectroscopic analyses. According to the X-ray crystallographic analysis data, in the crystals, NiL₂ and ZnL₂ are asymmetric binuclear complexes in which metal atoms have a different coordination environment composed of ligand oxygen atoms (c.n.= 6 and 5) and are bridged by oxygen atoms, both chelate and from one of the methoxy groups. The mixed-ligand complex [NiL(dpm)]₂ (dpm = dipivaloylmethanate: 2,2,6,6-tetramethyl-3,5-heptandionate) has a similar binuclear structure. It is found that complexes with non-fluorinated ligands pass to the gas phase as monomers whereas fluorine-containing complexes pass as dimers. The compounds are paramagnetic, except zinc complexes. In the binuclear complexes based on non-fluorinated ligands, a ferromagnetic exchange interaction of magnetic moments is observed while for fluorine-containing ligands it is antiferromagnetic.

By the reaction of a [BiX₆]³⁻ solution in HBr with the bromide salt of bis-(3-methyl-1-pyridino)ethane ((3-MePy)₂C₂Br₂) the bromobismuthate complex ((3-MePy)₂C₂)₄[Bi₂Br₁₁][BiBr₆] (1) is obtained, which, when kept in the Br₂ solution in HBr, transforms into ((3-MePy)₂C₂)₃ [Bi₂Br₁₁](Br₃) (2). Compounds 1 and 2 are characterized by single crystal XRD.

4-Bromo-7-phenylamino-2,1,3-benzothiadiazole (1) and 4-bromo-7-(3-pyridylamino)-2,1,3-benzo thiadiazole (2) are synthesized. Their crystal structure and photophysical properties are studied in comparison with the known phenylamino- and pyridylamino-derivatives of 2,1,3-benzothiadiazole. It is found that the aryl substituent and noncovalent interactions affect the absorption band positions and emission in a solid and a solution. It is shown that under the mechanical action on polycrystalline samples of compounds 1 and 2 a hypsochromic shift of the emission band occurs, which indicates the weakening of noncovalent intermolecular interactions.

Crystal and molecular structures of 3a-(p-tolyl)-3,3a-dihydrobenzo[d]pyrrolo[2,1-b]thiazole-1(2H)-one obtained by condensing 4-oxo-4-(p-tolyl)butane acid with 2-aminothiophenol are studied using XRD spectroscopy. The crystal of compound 1 occurs in the form of two crystallographically independent molecules. The crystal has no hydrogen bonds and stacking interactions, but the analysis of Hirshfeld surfaces shows that the molecules are weakly stabilized by non-covalent interactions between oxygen atoms and hydrogen atoms of methyl groups as well as by the interactions between hydrogen atoms and carbon atoms of the benzothiazole fragment.