The model catalytic hydrogenation process involving bimetallic Pt3Cr clusters is investigated using combined quantum-chemical methods DFT(PBE0)/def2tzvp with the NEB functional for geometry optimisations along the reaction pathway. Minimum energy pathway (MEP) curves have been constructed and the most important points - energy minima and transition states (TS) - have been carefully analysed. Geometries of intermediate structures at these points are determined and the activation barriers of individual reaction stages are evaluated. It is found that Pt3Cr clusters barrierlessly adsorb H2 and formamide molecules through any metal centre. The study shows how hydrogen migration occurs from one metal centre to another and to the substrate to be hydrogenated. A bimetallic catalyst composed of Pt3Cr model clusters exhibits lower activation energies in the test hydrogenation reaction compared to the catalysts based on Pt3V and Pt4.

A detailed study on the stages of catalytic reactions involving platinum and platinum-vanadium clusters has been carried out. Minimum energy pathways (MEP) of reactions have been constructed via the DFT/PBE0/def2tzvp method using NEB functional and optimized structures, and points of minima and transition states have been calculated. A two-step process for the conversion of formamide to methylamine under the action of H2 has been considered as a test reaction. The energy barriers of this reaction, not previously described in the literature, have been evaluated. It has been shown that the main changes in the structural characteristics of the reagents, as well as the migration of single H atoms from one metal center of clusters to another or to an organic substrate, are initiated at the molecular level by shifts corresponding to the vectors of normal vibrations of systems in transition states.

The activation of H2 molecules by Pt4 and Pt3V clusters was studied by the nudged elastic band (NEB) DFT/PBE0/def2tzvp quantum chemical method with construction of minimum energy paths (MEPs). In the case of Pt4 and Pt3V clusters, barrier-free dissociative adsorption of H2 molecules occurs at the platinum centers, while molecular adsorption of hydrogen occurs on the vanadium atom in Pt3V with a slight weakening of the H−H bond, but without its breaking. The specific features of coordination of H2 molecules are explained at the level of the MO method. Migration of the H atom from one cluster metal center to another in the model clusters (as probably in the case of hydrogen spillover) occurs at low activation barriers in the direction of the displacement vector corresponding to the normal vibrations of the system in the transition state. A significant role of Pt−H−Pt and V−H−Pt bridging groups in hydrogen migration has been revealed: they facilitate the transition of H atoms from one metal center of the cluster to another.

The sorption of Rh(III) chlorocomplexes from hydrochloric acid solutions by silica chemically modified with -aminopropyltriethoxysilane groups was studied. Under static conditions, dependences of the sorption of the indicated ion on time, acid concentration, and temperature were obtained, and sorption isotherms were plotted. It was found that the time required for establishing constant sorption values for Rh(III) ions from a 1 mol/l HCl solution is 35–40 min. The maximum capacity of the sorbent with respect to rhodium(III) ions, which the authors managed to achieve, is 0.42 mmol/g. Under the same conditions, to achieve constant values of sorption of Pt(IV), Ir(III), and Ir(IV) ions, 10 min of phase contact is sufficient, while the sorption of ions of these metals does not exceed 0.06 mmol/g. Using a combination of spectral methods (IR and electron spectroscopy), it has been shown that in the process of establishing the sorption equilibrium, the Rh(III) hexachloride complex undergoes hydrolytic transformations, and an aquated ion of the [RhCl5(H2O)]2– composition passes into the sorbent phase, and with an increase in temperature — trans-[RhCl4(H2O)2]–. In this case, during the sorption of [PtCl6]2– and [IrCl6]2– ions, their complex state does not change, and they pass into the sorbent phase in the form of hexachloroplatinate (IV) ion and hexachloroiridate (IV) ion, respectively. Ir(III) ions behave similarly to Rh(III), aquatation processes occur, and the [IrCl4(H2O)2]– anion is sorbed. Since the chlorocomplexes of Ir(III) are adsorbed by the sorbent under study better than Ir(IV), in order to separate rhodium from iridium, one should not allow the reduction of Ir(IV) to a lower oxidation state. Experiments were carried out on the desorption of sorbed ions of platinum metals with a 10% ammonium chloride solution and a 3 mol/l HCl solution. It was found that the separation of the Rh(III)/Ir(IV) pair occurs at the elution stage.The work was carried out under agreement with the Ministry of Education and Science of the Russian Federation No. 075-15-2021-689 dated 09/01/2021, unique identification number 2296.61321X0010, with the participation of N. M. Bodnar, Candidate of Chemical Sciences, senior researcher (RTU MIREA), and G. V. Erlich, Doctor of Chemical Sciences, professor of the Faculty of Chemistry of Moscow State University named after M. V. Lomonosov.

Complexation during the sorption of palladium(II) ions from chloride media by chemically modified silicas has been studied. Due to the use of mesoporous silicas with an average pore diameter of >10 nm for their synthesis, these sorbents do not change their volume in aqueous and organic media and have high mass transfer characteristics. The dependences of the sorption of Pd(II) ions from chloride solutions under static conditions as a function of time, HCl concentration, and Cl – ion have been obtained; sorption isotherms are constructed. Based on the experimental data, a conclusion has been made about the coordination mechanism of sorption, which has been proved by a combination of spectral methods (IR, UV-VIS, and X-ray photoelectron spectroscopy). The structure of sulfur-containing sorbents and their complexes with palladium has been modeled using the DFT M06 quantum-chemical method in the def2tzvp basis in the gas phase and taking into account the H 2 O solvent. The performed calculations make it possible to substantiate the nature of the dependence of sorption on the acid concentration and to confirm the formation of palladium(II) complexes with bidentate coordination of ligands in the silica phase modified with thiosalicylic and mercaptoacetic acids.

Сочетание современных методов элементного анализа с сорбционным концентрированием обеспечивает надежное определение металлов платиновой группы в объектах со сложным матричным составом.К настоящему времени для этих целей синтезировано большое количество сорбентов на основе различных полимеров, неорганических оксидов, углеродных и других материалов.Сорбенты должны отвечать требованиям высокой селективности, эффективности извлечения платиновых металлов и на стадии сорбции, и на стадии элюирования, устойчивости в кислых средах, а также многократности использования, предпочтительно в динамических условиях.Общепризнанно [1], что наилучшую селективность и эффективность извлечения ионов металлов из сложных по составу растворов обеспечивает так называемая технология молекулярного распознавания (ТМР), использующая сорбенты на основе кремнезема с химически привитыми органическими лигандами макроциклического и/или линейного строения [2].В настоящей работе мы описываем способ сорбционной пробоподготовки анализируемых технологических растворов, содержащих платину, палладий и родий, на основе ТМР.Разработанные нами сорбенты на основе кремнезема с химически привитыми замещенными алкиларилсульфидами [3] обеспечивают извлечение ионов палладия(II) из растворов 0.1 -4 М HCl, содержащих до 90 г/л хлорид-иона и 10 4 -10 5 -кратные избытки макрокомпонентов, и последующее количественное элюирование палладия аммиачным буферным раствором (pH 10).Сорбент на основе кремнезема с химически привитым полиэтиленимином [4] может быть использован для селективного выделения ионов платины(IV) и родия(III) из растворов 0.1 -6 М HCl и их разделения на стадии элюирования 5%-м раствором тиомочевины в 0.01 M HCl и 20%-м раствором хлорида аммония, соответственно.Разработан способ пробоподготовки сложных растворов с использованием хроматографических колонок диаметром 8 мм, наполненных синтезированными сорбентами, имеющими оптимальные фазово-структурные характеристики с точки зрения гидролитической стабильности, ненабухаемости и скорости сорбции.Высокая селективность выделения целевых компонентов подтверждена опытами на реальных растворах переработки медно-никелевых шламов.Показано, что стабильность работы предлагаемых сорбентов сохраняется в течение не менее 10 циклов сорбции-десорбции.

This works deals with isolation of chloro complexes of platinum metals, in particular [IrCl6]3– and [IrCl6]2–, from hydrochloric acid solutions with different content of chloride ions by sorption method. Sorbents used were modified silicas obtained by the chemical grafting of short-chain polyethyleneimines (PEI) to their surface followed by crosslinking and quaternization to form a thin layer of supported ionic liquids. A PEI with low molecular weight (MW 600, ~12 units) and preferably linear molecules was selected. Mobility of polyethyleneimine chains determines the possibility of its multipoint grafting to silica surface. Procedures for the synthesis of sorbents and their structural characteristics have been reported. Dependences of Ir(III) and Ir(IV) sorption on HCl, H+, and Cl– concentration have been revealed. Sorption equilibrium is reached over 2–5 min, which is typical for materials based on mesoporous silica and indicates anion-exchange mechanism of binding. A hot NH4Cl solution has been used for the quantitative desorption of Ir(IV) ions. The sorbents were tested for separation of Ir(IV) from Pt(IV) and Rh(III). Obtained results may be recommended for the recovery of platinum metal ions from chloride solutions of complex composition.

The reaction of [Pt(NH3)4]Cl2 with NH4VO3 in alkaline solution in an autoclave at 190°C was studied. The solid autoclave thermolysis product was characterized by the methods of X-ray phase analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, dynamic light scattering, and elemental analysis. The product is represented by two phases: Pt and a Pt3V solid solution in the form of two types of particles of different morphology with a size less than 1 µm. The reaction stoichiometry {9[Pt(NH3)4]Cl2, 18NH4VO3, 18KOH} corresponds to the found amount of free ammonia (14NH3) formed under the selected conditions.

The solid-phase reaction of [Pt(NH3)4]Cl2 and (NH4)6Mo7O24 under argon in the temperature range from 50 to 500°C was studied by thermal analysis and mass spectrometry. According to the X-ray powder diffraction, X-ray photoelectron spectroscopy, and elemental analysis data, the product consists of ordered Pt3Mo phase with an insignificant amount of molybdenum(VI) oxide. The described reaction is accompanied by reduction of the metals, which is promoted by Pt2+ ions in the presence of ammonia.

A study was made of the thermal interaction in the system [Pt(NH3)4]Cl2–(NH4)10[H2W12O42] (Pt : W = 1 : 2) in an argon atmosphere, which begins at a temperature above 200°C, occurs through a number of successive steps, and ends at 450°C. The intermediate products formed in the solid and gas phases were investigated by thermogravimetric analysis, differential thermal analysis, mass spectrometry, X-ray powder diffraction analysis, X-ray photoelectron spectroscopy, and elemental analysis. The end solid products obtained at 542 and 550°C were platinum-based solid solutions Pt1 – xWx with the unit cell parameters a = 3.9261(6) and 3.9262(3) Å, respectively, and also the tungsten oxide phases: hexagonal h-WO3 and monoclinic m-WO3. A reaction was proposed to describe the interaction of the components in the considered system. The obtained results can form the basis of methods for producing catalysts based on platinum and tungsten for various chemical processes.

This article provides information on one of the most interesting elements in the D.I. Mendeleev Periodic Table - ruthenium, discovered 175 years ago by the outstanding Russian chemist Karl Karlovich Klaus. Its most important physical properties, a variety of oxidation states, and a tendency to form countless compounds have been noted, mocking it unique and indispensable in all areas of science, technology, and in society. We have taken into consideration the structure of ruthenium consumption today as well as a few prospects for its future use.

A possibility of obtaining bimetallic Pt-W particles in an autoclave at 190°C in an alkaline solution was shown. Structure of the obtained particles was studied by dynamic light scattering and X-ray phase analysis. A possible route for the reduction of platinum and tungsten in the selected conditions to the metallic state with ammonia in statu nascendi was proposed.

Sequential thermal transformations of a 3[Pd(NH3)4]Cl2–2(NH4)2Cr2O7 mixture (Pd : Cr molar ratio, 3 : 4) are studied via thermal analysis and mass spectrometry in an argon atmosphere and the temperature range of 50 to 550°C. XRD and elemental analysis show that the solid product obtained after thermolysis of the mixture under the selected conditions is a Pd1 − xCrx palladium-based solid solution that is isostructural to Pd (cell parameter a = 3.8921(5) Å) and the Cr2O3 oxide phase. A model of the solid-phase transformations in the mixture in an argon atmosphere is proposed that includes the formation of palladium and chromium metallic phases.