M. G. Gantman

The Evolution of Reactive Ligands in the Catalysis of Radical Processes by Copper Complexes

Abstract Two radical reactions (addition of CCl4 to the double bond of oct-1-ene and oxidation of dodecane-1-thiol with air oxygen) catalyzed by copper complexes have been investigated. Various nitrogen-containing compounds (aliphatic and aromatic amines, aminoalcohols, aminoacids) were used as the ligands. In both cases, products of ligand transformation have been observed, products of the transformations have been identified by GLC-MS. In case of the CCl4 addition, the reaction can be initiated by the either copper complex or the ligand. In case of the thiol coupling, the reaction proceeds as a conjugated oxidation of both the thiol and the ligand. A correlation between the donor ability of the ligand and its reactivity has been found. GRAPHICAL ABSTRACT

Immobilized copper- and molybdenum-containing ionic liquids in oxidation of sulfides

The synthesis and comparative analysis of catalytic properties of Cu- and Mo-containing ethylpropylimidazolium derivatives immobilized on silica-series mineral supports have been performed. The oxidation of diethyl sulfide and methyl phenyl sulfide with oxygen and hydrogen peroxide in a hydrocarbon medium has been studied as a model process. The catalyst based on ethylpropylimidazolium polymolybdates is the most active and stable in the oxidation of methyl phenyl sulfide.

Reactions of polyhalomethanes with olefins catalyzed by copper complexes with aromatic amino alcohols

Copper complexes with amino alcohols structurally similar to ephedrin (1-phenyl-3-(N-methylamino)propan-1-ol and 1-phenyl-2-(N-methylamino)ethanol) are catalytically very active in the free-radical addition of CCl4 and CBr4 to linear alk-1-enes. These amino alcohols themselves are initiators of radical addition reactions, and, in the reaction with CBr4, they are more active than the metal complexes. In the presence of the amino alcohols, as distinct from classical radical initiators, the reaction is highly selective and affords an addition product. An analysis of kinetic equations and the data obtained for the reaction involving CHCl3 suggest that the amino alcohols and the corresponding metal complexes are involved in different ways in the addition of CCl4 and CBr4 to linear alk-1-enes.

Reactive ligands in radical processes catalyzed by copper complexes

The effect of the reactivity of donor ligands on the catalytic properties of copper complexes in the oxidative dimerization of mercaptans is considered. Catalytic compositions containing metal complexes in an excess of organic reagent ligands, which can show pronounced reductive properties (aromatic amines) or, on the contrary, oxidative properties (dimethyl sulfoxide) toward substrates, exhibit the greatest activity. In the course of the oxidation of mercaptans catalyzed by copper complexes, redox reactions accompanied by not only a change in the oxidation state of the metal but also the direct interaction of a substrate with an organic donor occur. In the presence of aromatic amines, the coupled oxidation of thiols and amines occurs, whereas dimethyl sulfoxide participates in the reaction as an oxidizing agent.

Non-innocent ligands in copper complexes catalyzed oxidation of thiols

ABSTRACT Copper(II) chloride complexes with nitrogen-containing ligands (amines, amides, heterocycles) were studied as catalysts of selective oxidation of thiols to disulfides. This process has an important biochemical analogue – the formation of disulfide bridge in proteins [Wang C, Wesener SR, Zhang H, Cheng Y-Q. An FAD-dependent pyridine nucleotide-disulfide oxidoreductase is involved in disulfide bond formation in FK228 anticancer depsipeptide. Chem and Biol. 2009;16:585–593]; which affects their activity [Zhang L, Chou CP, Moo-Young M. Disulfide bond formation and its impact on the biological activity and stability of recombinant therapeutic proteins produced by Escherichia coli expression system. Biotech Adv. 2011;29:923–929]. Also, thiol oxidation is an important process of oil sweetening. The search for effective and stable catalysts for this reaction is still topical [Ganguly SK, Das G, Kumar S, Sain B, Garg MO. Mechanistic kinetics of catalytic oxidation of 1-butanethiol in light oil sweetening. Catal Tod. 2012;198:246–251]. This article describes a mechanistic study of thiol oxidation and non-innocent ligands transformations during this reaction. The studied ligands are capable of oxidizing thiols, the reaction being followed by reoxidation of the reduced forms of the ligands with air oxygen. The oxidative activity of the ligand correlates with catalyst activity for thiol oxidation. GRAPHICAL ABSTRACT