An isolable dialkylsilylene and its derivatives. A step toward comprehension of heavy unsaturated bonds

Synthesis and structural characteristics of an isolable dialkylsilylene and its application for the synthesis of unique silicon unsaturated compounds such as silanechalcogenones, silaketenimines, a tetrasila-1,3-diene and a trisilaallene are discussed. Because the silylene has no aromatic or alkenyl substituents, the derivatives are mostly free from the influence of the pi-conjugative substituents, and hence, are suitable for exploring the intrinsic or standard characteristics of the unsaturated bonds. Using perturbation molecular orbital (PMO) theory, the importance of pi-sigma* mixing is emphasized to figure out the key issues of heavy unsaturated bonds.