| Research Abstract |
During the project term, the main goal of the investigation, synthesis of the cyclobutadiene dianions consisting of the heavier group 14 elements, was achieved. Thus, the potassium salts of the disiladigerma-, disilagermastanna- and tetrasilacyclobutadiene dianion derivatives were successfully synthesized and structurally characterized. The possible aromaticity of these 6π-electron species was verified by both experimental and computational methods to establish the essential non-aromaticity of the "heavy" cyclobutadiene dianions. The reactivity of these dianionic compounds was also studied in details to reveal their great synthetic potentials for the formation of the unique cyclic and polycyclic organometallic compounds, that are not available by any other synthetic routes. The tetrasila-and trisilagermacyclobutadiene dianions have been successfully utilized as the novel ligands for transition metals complexes of different types: sandwich, half-sandwich, piano-stool, etc. Thus, a variety of W, Mo, Zr, Hf, Co, Fe, Ru, Rh-complexes featuring tetrasilacyclobutadiene ligand have been prepared and characterized. As the related 6π-electron species, the "heavy" analogue of the aromatic cyclopentadienide ion Cp-, disilagermacyclopentadienide ion, was also synthesized and proved to be an aromatic compound. It was also used as a ligand for transition metal complexes: novel metallocenes with the "heavy" cyclopentadienyl ligand were synthesized as the analogues of the classical ferrocene and ruthenocene. The particular heavy" ligand-to-transition metal bonding situation was thoroughly studied from both experimental and theoretical points of view. The search for the practical application of the newly synthesized complexes, having either "heavy" cyclobutadiene or "heavy" cyclopentadienyl ligands, in the field of material science is now under way.
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