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Three indolyl- and pyrrolylsilylamines 1–3 were prepared from lithiated heterocyclics and fluorosilylamines. Further reaction with di- tert -butyldifluorosilane led to the fluorosilylpyrrolylsilylamines 4 and 5 . The fluorosilylpyrrolylsilylamine 6 was prepared by reaction of bis(fluorodiisopropylsilyl)amine and lithium pyrrolide. Lithiiation with n-butyllithium of 4–6 solved in THF gave the iminosilane-LiF adducts 7–9 ; in contrast, lithiation of 5 in n-hexane led to the lithium fluorosilylamid 10 . Heating of the iminosilane-LiF adduct 7 gave the bicyclic system 11 , an intramolecularly stabilized iminosilane. Addition of chlorotrimethylsilane to 9 led to fluorine-chlorine exchange and elimination of lithium chloride. The product is the intermolecular stabilization of the intermediate iminosilane as a four-membered ring 12 . The X-ray structures of 1, 11 and 12 have been determined.

Four-membered heterocycles (2, 3, 4, 5, 7) are formed in [2 + 2]-cycloadditions of the SiN double bond of di-tert-butyl(di-tertbutylphenylsilyl)iminosilane (1) with compounds including PN (2), CC (3), C0 (4, 5), and CN (7) double bonds. For example: di-tert-butyl(di-tert-butylphenylsilyl)iminosilane (1) reacts with bis(trimethylsilyl)amino-(trimethylsilyl)iminophosphane under formation of the 1,3-diaza-2-phospha-4-silacyclobutane (2). The 1-aza-2-silacyclobutane (3) is obtained in the reaction of the iminosilane (1) with ethylvinylether. Treatment of 1 with 2-methylpropenal leads to the formation of the 1-aza-3-oxa-4-silacyclobutane (4). The 1-aza-3-silacyclobutane (5) is formed in the reaction of the iminosilane 1 and tert-butylisocyanate. A 1,3-silylgroup migration from the nitrogen to the oxygen occurs in the reaction of 1 with trimethylsilylisocyanate. The aminonitril (6) is obtained. The 1,3-diaza-4silacyclobutanone (7) is the product of the reaction of 1 and phenylisocyanate. The crystal structures of 2, 3 and 7 are reported.