ADDUCTS OF PLATINUM(IV) NITRATE COMPLEXES WITH 15-CROWN-5 ETHER
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ADDUCTS OF PLATINUM(IV) NITRATE COMPLEXES WITH 15-CROWN-5 ETHER* P. A. Topchiyan1,2**, D. B. Vasilchenko1, I. A. Baidina1, and I. V. Korolkov1
The possibility of isolating platinum(IV) nitrate complexes to the solid phase from a nitric acid solution of platinum in the form of adducts with dibenzo-18-crown-6, 15-crown-5, and 12-crown-4 ether is studied. It is found that when nitric acid solutions containing 15-crown-5 ether (15-C-5) are evaporated, a polycrystalline product consisting of mainly a mixture of phases with the compositions (H3O⊂15-C-5)2[Pt(NO3)6] (1), (H3O⊂15-C-5)2(15-C-5)[Pt(NO3)6]⋅2H2O (2), and (15-C-5)[Pt4(μ3-OH)2(μ2-OH)4(NO3)10]⋅3H2O (3) is formed. The structure of the mentioned compounds is established by single crystal X-ray diffraction. In the case of dibenzo-18-crown-6 ether, the interaction with a nitric acid solution of platinum results in the formation of a poorly soluble tetranitro derivative of macrocyclic ether. Evaporation of nitric acid solutions of platinum containing 12-crown-4 ether does not allow the preparation of a solid crystalline phase. DOI: 10.1134/S0022476620090097 Keywords: platinum, nitrate complexes, crown ethers, single crystal X-ray diffraction analysis.
INTRODUCTION Platinum and palladium nitrates have established themselves as efficient precursors to obtain heterogeneous catalysts containing mentioned precious metals in a highly dispersed state, up to isolated atoms fixed on an oxide support [1, 2]. These systems are widely used in catalytic neutralization processes of toxic components of exhaust gases such as NOx and CO [3, 4]. A high lability of NO3− ligands in nitrate complexes of platinum and palladium ensures not only ready binding with the carrier surface but also a further transformation of the precursor into an active catalyst component under sufficiently mild conditions of thermal treatment [5]. Unlike palladium nitrate (cis-[Pd(H2O)2(NO3)2]) [6], the so-called solution of platinum(IV) nitrate obtained by dissolving platinum(IV) hydroxide ([Pt(H2O)2(OH)4]) in concentrated nitric acid is a complex mixture of mononuclear aqueous nitrate ([Pt(H2O)6–n(NO3)n]4–n) and polynuclear aqueous hydroxyl nitrate (e.g., [Pt2(μ2-OH)2(NO3)8]2– or [Pt4(μ3-OH)2(μ2-OH)4(NO3)10]) complexes of platinum(IV) [7, 8]. A direct application of the platinum(IV) nitrate solution as a precursor for obtaining heterogeneous catalysts is unreasonable, firstly, due to a large excess of concentrated nitric acid, and secondly, instability of this solution: when diluted with water, rapid hydrolysis is observed with the formation of hydrated platinum dioxide [9]. Moreover, a solution of platinum nitrate contains
1
Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia; **[email protected]. 2Novosibirsk State University, Novosibirsk, Russia. Original article submitted April 9, 2020; revised April 13, 2020; accepted April 14, 2020. *
Supplementary materials for this article are available for authorized users at doi 10.1134/S0022476620090097.
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