A. A. Fedorova

Physicochemical properties of manganese-containing oxides with a spinel structure prepared with the use of ammonium nitrate and their catalytic activity in carbon monoxide oxidation

Oxide catalysts with the spinel structure with the molar ratios between components Co/Mn = 1: 2, Cu/Mn = 1: 2, and Cu/Co/Mn = 2: 2: 3 (samples I–III, respectively) have been prepared by the decomposition of metal nitrate hydrate solutions in an ammonium nitrate melt. Sample IV with the ratio Cu/Co/Mn = 2: 2: 3 containing 80% γ-Al2O3 is obtained by the addition of γ-Al2O3 powder to the initial melt. The catalysts are characterized using X-ray diffraction analysis, electron microscopy, and local X-ray analysis. Catalytic activity in the reaction of CO oxidation increased in the order I < II < III < IV. The proposed method is simple, and the synthesis is rapid. Oxides with the spinel structure homogeneous in composition and morphology without any impurities can be prepared by this method. These oxides exhibited high catalytic activity in the reaction of carbon monoxide oxidation.

Synthesis and crystal structures of nitratocobaltates Na2[Co(NO3)4], K2[Co(NO3)4], and Ag[Co(NO3)3] and potassium nitratonickelate K2[Ni(NO3)4]

The cobalt(II) and nickel(II) nitrate complexes with an island structure (Na2[Co(NO3)4] (I) and K2[Co(NO3)4] (II)] and a chain structure [Ag[Co(NO3)3] (III) and K2[Ni(NO3)4] (IV)] are synthesized and investigated using X-ray diffraction. In the anionic complex [Co(NO3)4]2− of the crystal structure of compound I, the Co coordination polyhedron is a twisted tetragonal prism formed by the O atoms of four asymmetric bidentate nitrate groups. In the anion [Co(NO3)4]2− of the crystal structure of compound II, one of the four NO3 groups is monodentate and the other NO3 groups are bidentate (the coordination number of the cobalt atom is equal to seven, and the cobalt coordination polyhedron is a monocapped trigonal prism). The crystal structures of compounds III and IV contain infinite chains of the compositions [Co(NO3)2(NO3)2/2]− and [Ni(NO3)3(NO3)2/2]2−, respectively. In the crystal structure of compound III, seven oxygen atoms of one monodentate and three bidentate nitrate groups form a dodecahedron with an unoccupied vertex of the A type around the Co atom. In the crystal structure of compound IV, the octahedral polyhedron of the Ni atom is formed by five nitrate groups, one of which is terminal bidentate. The data on the structure of Co(II) coordination polyhedra in the known nitratocobaltates are generalized.

Synthesis and crystal structures of zirconium(IV) nitrate complexes (NO2)[Zr(NO3)3(H2O)3]2(NO3) 3, Cs[Zr(NO3)5], and (NH4)[Zr(NO3)5](HNO3)

The zirconium nitrate complexes (NO2)[Zr(NO3)3(H2O)3]2(NO3)3 (1), Cs[Zr(NO3)5] ((2), (NH4)[Zr(NO3)5](HNO3) (3), and (NO2)0.23(NO)0.77[Zr(NO3)5] ((4) were prepared by crystallization from nitric acid solutions in the presence of H2SO4 or P2O5. The complexes were characterized by X-ray diffraction. The crystal structure of 1 consists of nitrate anions, nitronium cations, and [Zr(NO3)3(H2O)3]+ complex cations in which the ZrIV atom is coordinated by three water molecules and three bidentate nitrate groups. The coordination polyhedron of the ZrIV atom is a tricapped trigonal prism formed by nine oxygen atoms. The island structures of 2 and 3 contain [Zr(NO3)5]− anions and Cs+ or NH4+ cations, respectively. In addition, complex 3 contains HNO3 molecules. Complex 4 differs from (NO2)[Zr(NO3)5] in that three-fourth of the nitronium cations in 4 are replaced by nitrosonium cations NO+, resulting in a decrease in the unit cell parameters. In the [Zr(NO3)5]− anion involved in complexes 2–4, the ZrIV atom is coordinated by five bidentate nitrate groups and has an unusually high coordination number of 10. The coordination polyhedron is a bicapped square antiprism.

Trifluoroacetate complexes of 3d elements: specific features of syntheses and structures

Data on the syntheses and structures of trifluoroacetates of 3d elements mainly based on our results are reviewed. Specific features of the coordination chemistry of mono-, oligo-, and polynuclear trifluoroacetate complexes are successively considered. Special attention is given to oxo- and fluorotrifluoroacetates containing the trinuclear triangular fragment as a structural unit. Structural features of trifluoroacetates compared to other carboxylates are discussed.

Mixed spinel-type Ni-Co-Mn oxides: synthesis, structure and catalytic properties

Abstract Mixed spinel-type oxides Co1.8Mn1.2O4, Ni0.33Co1.33Mn1.33O4 and Ni0.6Co1.2Mn1.2O4 prepared by thermal decomposition of nitrates have been studied in ethanol steam reforming reaction. Ni0.6Co1.2Mn1.2O4 demonstrated the highest activity among the oxides tested. Specificity of the cation distribution in the samples and their oxygen mobility have been studied by X-ray absorption spectroscopy and oxygen isotope heteroexchange, respectively. Doping of mixed cobalt-manganese spinel with Ni results in Mn redistribution between 3+ and 4+ oxidation states, thus increasing oxygen diffusion coefficient and the catalytic activity.

Synthesis and crystal structures of nitratocobaltates Na{sub 2}[Co(NO{sub 3}){sub 4}], K{sub 2}[Co(NO{sub 3}){sub 4}], and Ag[Co(NO{sub 3}){sub 3}] and potassium nitratonickelate K{sub 2}[Ni(NO{sub 3}){sub 4}]

The cobalt(II) and nickel(II) nitrate complexes with an island structure (Na2[Co(NO3)4] (I) and K2[Co(NO3)4] (II)] and a chain structure [Ag[Co(NO3)3] (III) and K2[Ni(NO3)4] (IV)] are synthesized and investigated using X-ray diffraction. In the anionic complex [Co(NO3)4]2− of the crystal structure of compound I, the Co coordination polyhedron is a twisted tetragonal prism formed by the O atoms of four asymmetric bidentate nitrate groups. In the anion [Co(NO3)4]2− of the crystal structure of compound II, one of the four NO3 groups is monodentate and the other NO3 groups are bidentate (the coordination number of the cobalt atom is equal to seven, and the cobalt coordination polyhedron is a monocapped trigonal prism). The crystal structures of compounds III and IV contain infinite chains of the compositions [Co(NO3)2(NO3)2/2]− and [Ni(NO3)3(NO3)2/2]2−, respectively. In the crystal structure of compound III, seven oxygen atoms of one monodentate and three bidentate nitrate groups form a dodecahedron with an unoccupied vertex of the A type around the Co atom. In the crystal structure of compound IV, the octahedral polyhedron of the Ni atom is formed by five nitrate groups, one of which is terminal bidentate. The data on the structure of Co(II) coordination polyhedra in the known nitratocobaltates are generalized.