Abstract
Synthesis, structure, and reactions of novel acyclic and cyclic disilenes are discussed in detail. Due to the distinctive electronic and steric effects of trialkylsilyl substituents, tetrakis (trialkylsilyl) disilenes show interesting structural features around Si=Si bonds, electronic spectra, and reactions. Photochemical and thermal interconversion among Si4R6 isomers including a cyclotetrasilene, a silylcyclotrisilene, and a bicyclo [1.1.0] tetrasilane occurs without apparent participation of the corresponding tetrasila-1, 3-diene. In contrast to parent spiropentadiene, which is the simplest spiro-conjugation system but has been missing as an isolable molecule in carbon chemistry, a synthesized spiropentasiladiene is thermally very stable and shows remarkable spiroconjugation between the two ring π systems. In contrast to carbon allenes, the skeleton of a trisilaallene, the first stable silicon compound with formally sp-hybridized silicon atom, is significantly bent and remarkably fluxional. Tetrasilyldisilenes are useful reagents for the synthesis of novel types of organosilicon compounds such as η2-disilene transition metal complexes and a 1, 3-disilabicyclo [1.1.0] butane.
