Research on the Synthesis, Structure, and Reactivity of Aromatic Compound Consisting of Heavier Main Group Elements

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Aromatic hydorocarbons such as benzene and naphthalene, are fundamental group of organic compounds, and also plays important roles in organic chemistry. In contrast, the chemistry of stable metallaaromatic compounds such as sila- and germa- aromatic systems, in which skeletal atom(s) are partially replaced by heavier Group 14 elements, is new, and have been recently developed. In this project, we investigated the chemistry of stable aromatic compounds consisting of heavier group 14 elements ; the development of synthetic methods, analysis of structure, property, and reactivity of them.We succeeded in synthesize and characterize cyclotrisilenylium ion by the oxidative desilylation reaction of cyclotrisilene bearing extremely bulky triorganosilyl groups. Cyclotrisileniylium ion has near regular triangle three membered ring indicating its aromatic character in analogy with cyclopropenylium ion with 2π aromatic system. On the other hand, dipotassium salt of tetrasilacyclobutadiene dianion as heavier analogue of cyclobutadiene dianion with 6π aromatic system synthesized by the reductive debromination and additional two-electron reduction of 1,2,3,4-tetrabromocyclotetrasilane, has large bent four membered ring coordinated by two potassium cations up and below, and we concluded that heavier cyclobutadiene dianion is non-aromatic by the reason why planer three-coordinate geometry is not preferred in negatively charged organosilicon compounds. Additionally, we also succeeded in the synthesis of disilagermacyclopentadienide ion as 6π electron aromatic compound.