SYNTHESIS AND PROPERTIES OF RUTHENIUM CLUSTER COMPLEXES

Abstract

Methods for the synthesis of ruthenium cluster complexes based on carbonyl and amine-containing organic bifunctional ligands have been developed. The structure of the obtained combinations of clusters were determined on the basis of IR spectroscopy data, thermogravimetry, and elemental analysis. Samples of ligands I and II were obtained by condensation of carboxylic acid chlorides of cyclopentane and cyclohexane with ethylene followed by replacement of the chlorine atom by amine groups. To obtain cluster complexes of ruthenium with the synthesized ligands the ruthenium trichloride salt (RuCl3) was dissolved in water, and the calculated amount of sodium borohydride was added in portions to the resulting solution under vigorous stirring in nitrogen atmosphere. Rapidly emerging black-dispersed nanoparticles of metallic ruthenium did not precipitate. When organic ligands I and II are added, the corresponding cluster compounds III and IV are formed, which gradually over 45 min. precipitated from an aqueous solution. The resulting dark-brown precipitates were washed with distilled water and dried in a nitrogen atmosphere at a temperature of 35-400C. The melting temperatures of the synthesized compounds were determined, the components for cluster III - 2060С and cluster IV - 2220С (with decomposition). The IR spectra of cluster compounds show intense absorption bands characterizing the presence of both the ketone carbonyl group and the amine fragment. The absorption bands of ketone groups in cluster compounds are shifted towards higher frequencies compared to the initial ligands. A similar picture is also observed when comparing the IR vibrations of CN bonds in the initial ligands and the corresponding cluster compounds. The results of elemental analysis confirm the structures of cluster compounds and are in complete agreement with the concept that cluster compounds are formed upon the reduction of ruthenium salts with metal hydrides in an aqueous solution. Apparently, in this case, the most stable ruthenium clusters with tetrahedral structure are formed.. Thermogravimetric analysis made it possible to establish the presence of a peak at a temperature of 3180C with a mass number of 744.8 , corresponding to a cluster combination of four ruthenium atoms. At each stage of decomposition, the experimental mass losses are in good agreement with the calculated values. Keywords: synthesis, ruthenium, cluster complexes, amine and caryonyl containing ligands, bifunctional ligands, cyclopentyl amino ketone, cyclohexyl amino ketone.