Thermal Dissociation of Disilenes into Silylenes

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Abstract
Extremely hindered and stable disilenes (Tbt(Mes)Si=Si(Mes)Tbt {Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Mes = 2,4,6-trimethylphenyl. (Z)-1: cis-isomer, (E)-1: trans-isomer}) underwent dissociation under very mild conditions (ca. 70 °C) into a divalent silicon species (Tbt(Mes)Si: (2)), which was trapped by methanol, triethylsilane, 2,3-dimethyl-1,3-butadiene, elemental sulfur, and elemental selenium to afford the corresponding adducts in good yields. Silylene 2 reacted with some carbon–carbon multiple-bond compounds to afford the corresponding [1 + 2] cycloadducts, among which the adduct with 3,3,6,6-tetramethylthiacyclohept-4-yne was established by an X-ray diffraction analysis. Silylene 2 also reacted with naphthalene and benzene to give the corresponding adducts, 15 and 17, respectively, the molecular structures of which were confirmed by X-ray crystallographic analyses. The formation of 15 and 17 represents the first example of [1 + 2] cycloaddition of silylenes to aromatic compounds. The thermolysis of 15 and 17 regenerated silylene 2, which was trapped with triethylsilane. A kinetic study of the thermal dissociation of 1 gave the activation parameters, which were compared with those for E Z isomerization of previously reported disilenes.

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