ИСТИНА

A comparative study of thermally activated reactions of Ru3(CO)12 with oxadienes and aminovinylketones is reported. In order to rule out possible effects of substituents on the chemical behavior of organic ligands, we chose very similar ligands, viz., 4-phenylbut-3-en-2-one (1) аnd 4-dimethylaminobut-3-en-2-one (2). Structural and spectroscopic features of the complexes are discussed along with their possible transformation pathways within the context of competition of different functional groups. The influence of the amine group on the coordination patterns of the oxadiene moiety is noted.Complexes bearing a five-membered oxaruthenacycle are major products of the reactions. The olefin group of the oxaruthenacycle afforded in the reaction with 1 takes part in π-coordination to a ruthenium atom. Meanwhile, the olefin group in 2 is deactivated due to the amine group’s donor effect. Therefore, the π-coordination is possible only if the nitrogen atom is excluded from the common π-conjugated system of the ligand. When coordination to ruthenium atom, 2 undergoes isomerization with the formation of an imine C=N bond. This facilitates the migration of the СН=СН bond and as a consequence the carbon atoms in the α- and β-positions of the organic ligand form σ-bonds to ruthenium atoms. Upon formation of an oxaruthenacycle, the ligand loses a hydrogen atom. In the reaction with 1, an excess amount of the ligand acts as a hydrogen acceptor and undergoes reduction to the respective saturated ketone. To the contrary, an excess amount of Ru3(CO)12 acts as a hydrogen acceptor in reaction with 2 giving rise to hydride cluster [НRu6(CO)18]‾. Despite general similarity of both reactions, the presence of a donor amine group results in new types of coordination of the organic ligand to metal atoms and further in the isomerization of the oxadiene system, migration of the СН=СН bond and extra С-Н activation.