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Three binary fcc-structured alloys (fcc–Ir0.50Pt0.50, fcc Rh0.66Pt0.33 and fcc–Rh0.50Pd0.50) were 14 prepared from [Ir(NH3)5Cl][PtCl6], [Ir(NH3)5Cl][PtBr6], [Rh(NH3)5Cl]2[PtCl6]Cl2 and 15 [Rh(NH3)5Cl][PdCl4]·H2O, respectively, as single-source precursors. All alloys were prepared by 16 thermal decomposition in gaseous hydrogen flow below 800 °C. Fcc–Ir0.50Pt0.50 and fcc–Rh0.50Pd0.50 17 correspond to miscibility gaps on binary metallic phase diagrams and can be considered as 18 metastable alloys. Detailed comparison of [Ir(NH3)5Cl][PtCl6] and [Ir(NH3)5Cl][PtBr6] crystal 19 structures suggests that two isoformular salts are not isostructural. In [Ir(NH3)5Cl][PtBr6], specific 20 Br…Br interactions are responsible for crystal structure arrangement. Room temperature 21 compressibility of fcc–Ir0.50Pt0.50, fcc–Rh0.66Pt0.33 and fcc–Rh0.50Pd0.50 has been investigated up to 50 GPa 22 in diamond anvil cells. All investigated fcc-structured binary alloys are stable under compression. 23 Atomic volumes and bulk moduli show good agreement with ideal solutions model. For fcc–24 Ir0.50Pt0.50, V0/Z = 14.597(6) Å3·atom-1, B0 = 321(6) GPa, B0' = 6(1); for fcc–Rh0.66Pt0.33, V0/Z = 14.211(3) 25 Å3·atom-1, B0 =259(1) GPa, B0' = 6.66(9); for fcc–Rh0.50Pd0.50, V0/Z = 14.18(2) Å3·atom-1, B0 =223(4) GPa, 26 B0' = 5.0(3).
The products of thermal decomposition in an argon atmosphere of [Ni(NH3)6]3[Fe(CN)6]2 as a precursor has been studied. Decomposition products were studied up to 800◦C. Above 600◦C, all coordination bonds in the residues are broken with a formation of Ni3Fe, Fe, and free carbon with a small admixture of nitrogen. Elementary carbon can be easily separated from metals by treatment with a water solution of hydrochloric acid. Only carbon is responsible for the specific surface of the composite products. The released carbon has a high degree of graphitization and begins to oxidize in air above 500°C and is completely oxidized above 700°C.
Rhodium(III) octahedral complexes with amine and chloride ligands are the most common starting compounds for preparing catalytically active rhodium(I) and rhodium(III) species. Despite intensive study during the last 100 years, synthesis and crystal structures of rhodium(III) complexes were described only briefly. Some [RhClx(NH3)6-x] compounds are still unknown. In this study, available information about synthetic protocols and the crystal structures of possible [RhClx(NH3)6−x] octahedral species are summarized and critically analyzed. Unknown crystal structuresof(NH4)2[Rh(NH3)Cl5],trans–[Rh(NH3)4Cl2]Cl·H2O,andcis–[Rh(NH3)4Cl2]Clarereported based on high quality single crystal X-ray diffraction data. The crystal structure of [Rh(NH3)5Cl]Cl2 was redetermined. All available crystal structures with octahedral complexes [RhClx(NH3)6-x] were analyzed in terms of their packings and pseudo-translational sublattices. Pseudo-translation lattices suggest face-centered cubic and hexagonal closed-packed sub-cells, where Rh atoms occupy nearly ideal lattices.
A hydrothermal synthesis of ZrW2-xMoxO8 (0 ≤ x ≤ 2) from the corresponding precursors is reported in this paper. High-temperature and high-pressure data are presented for the sample with x = 1.6. An increase in temperature initiates the phase transition from tetragonal precursor to orthorhombic-ZrW2-xMoxO8 (x = 1.6) with the subsequent formation of cubic and trigonal phases. The thermolysis parameter of the disordered cubic ZrW2-xMoxO8 (x = 1.6) phase is 803 K, and the coefficient of thermal expansion is α = -4.6∙10–6 K−1. Data on ZrW2-xMoxO8 (x = 1.6) structure as a function of pressure are obtained for the first time. Pressureinduced changes from cubic to orthorhombic ZrW2-xMoxO8 (x = 1.6) phase at 1.38 GPa are observed. The sample amorphization is irreversible during decompression.
In this paper we report high-pressure synchrotron x-ray powder diffraction data for the cubic ZrWMoO8. For the first time, extensive structural study of ZrWMoO8 solid solution as a function of pressure was performed. This study shows that disordered cubic-ZrWMoO8 (space group Pa) transforms to ordered cubic-ZrWMoO8 (space group P) at low pressure. A further high-pressure influence leads followed by amorphization of the sample at 2.2 GPa. All transformations are irreversible. Our work will have high impact in the design of new composite materials with well-defined thermal expansion, especially for applications under extreme conditions and high mechanic stress.
Thermal decomposition of (NH4)2[OsxPt1-xCl6] as single-source precursors for Os-Pt binary alloys has been investigated under ambient and high pressure up to 40 GPa. Thermal decomposition of mixed-metal (NH4)2[OsxPt1-xCl6] precursor in hydrogen atmosphere (reductive environment) under ambient pressure results in formation of β-trans[Pt(NH3)2Cl2] and α-trans-[Pt(NH3)2Cl2] crystalline intermediates as well as single and twophase Os—Pt binary alloys. For the first time, direct thermal decomposition of coordination compound under pressure has been investigated. A formation of pure metallic alloys from single-source precursors under pressure has been shown. Miscibility between fcc- and hcpstructured alloys has been probed up to 50 GPa by in situ high-pressure X-ray diffraction. Miscibility gap between fcc- and hcp-structured alloys does not change its positions with pressure up to at least 50 GPa.
Nitrogen-rich noble metal nitrides possess unique mechanical and catalytic properties, therefore their synthesis and characterization is of interest for fundamental solid state chemistry and materials science. In this study we have synthesized a singlesource precursor [Rh(NH3)6]3(N3)5Cl4 (Rh:N ratio 1:11). Its controlled decomposition in a laser-heated diamond anvil cell at 39 GPa resulted in a formation of rhodium pernitride, RhN2. According to the results of single-crystal X-ray diffraction RhN2 has arsenopyrite structure type crystal structure previously unknown for this compound (P21/c (no. 14).
Preparation of new bimetallic compounds, including double complex salts (DCSs), containing both a platinumgroup metal and a transition metal of the fourth period is of great interest since these compounds can act as precursors of bimetallic materials. One example of using such compounds is the preparation of ultrafine particles of solid solutions of metals or intermetallic compounds on various supports to fabricate highly efficient catalysts with a low content of noble
metals.
Compounds containing coordinated oxalate anions are important objects of synthetic chemistry and interesting precursors. For example, a lot of attention is given to salts with [M(C2O4)2]2– anions, where M = Co, Ni, Cu, Pt, Pd. On the one hand, the uniqueness of oxalate coordinated anions is due to the fact that they are easily obtained and are stable both in aqueous solutions and in the solid phase; on the other hand, they are thermally decomposed at relatively low temperatures, which makes them promising precursors for the fabrication of metallic and oxide materials.
Thermal decomposition of [Co(NH₃)₆][Fe(C₂O₄)₃]∙3H₂O in argon atmosphere, at a low heating rate (3°/min), and in large amounts of the initial complex (~0.1 mole), has been studied. It was possible to distinguish four decomposition steps upon heating: In the temperature range of 50⁻100 °C-the loss of crystal water; 100⁻190 °C-stability region of dehydrated complex; 230⁻270 °C-the range of stability of intermediate phase with the formula CoFe(NH₃)₂(C₂O₄)₂; 270⁻350 °C-thermal decomposition of the intermediate with the formation of metallic products and further air oxidation with the formation of Co1.5Fe1.5O₄. Catalytic properties of thermolysis products were tested in the decomposition reaction of H₂O₂ (inactive), oxidation of acetone (average activity), and decomposition of ammonium perchlorate (highly active).