Syntheses, Properties, and Reactivities of Unsaturated Ring Compounds Consisting of Silicon and Germanium

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We have studied the reactivity of unsaturated small ring compound consisting of heavier Group 14 Elements such as silicon and germanium. The following results have been obtained in this project(1)The Reaction of Cyclotrisilene : Synthesis and Structure of Cyclotetrasilenylium IonThe reaction of ^tBu_2MeSi-substituted cyclotrisilene with [Et_3Si(C_6H_6)]^+・TPFPB^-in benzene gave cyclotetrasilenylium・TPFPB^-(TPFPB-=(C_6F_5)_4B^-) as air-and moisture-sensitive yellow crystals. X-ray crystallography revealed that the cyclotetrasilenylium ion is not only a free cation without the Interaction with counter anion and solvent molecules, but a 2π-electron homoaromatic compound consisting of silicon(2)Reactivities of Cyclotetrasilenylium Ion : Synthesis and Structure of Cyclotetrasilenyl Radical and Cyclotetrasilenylide IonThe reaction of the Cyclotetrasilenylium ion^-with bulky trialkylsilylsodium afforded cyclotetrasilenyl radical as a stable crystalline compound through the one electron reduct … More ion. The crystallographic analysis reveals that the cyclotetrasilenyl radical is a free silyl radical, having an allyl type delocalized structure, without any intermolecular interaction. Two electron reduction of the Cyclotetrasilenylium ion was also achieved by Li, Na, and KC_8 in diethyl ether to give cyclotetrasilenide ion. Stepwise chemical oxidation of cyclotetraslienid successfully regenerates the cyclotetrasilenyl radical and the Cyclotetrasilenylium Ion, indicating that cyclotetrasilenyl cation, radical, and anion show chemically reversible two electron redox system on the allyl type silicon π-electron system(3)The Reaction of Disilagermirene with Divalent Species of Germanium and TinDisilagermirene derivatives with Si=Si or Si=Ge double bond react with dichlorogermylene-1,4 dioxane complex to give disiladigermetene, which have an endocyclic Ge=Ge double bond. The same type ring expansion took place in the reaction of disilagermirenes with dichlorostannylene-1,4 dioxane complex to afford unsaturated four membered ring compound bearing Ge=Sn double bond Less