  silylenes are chemical compounds containing a divalent silicon atom without any electrical charge. both dicoordinate and tricoordinate silylenes are reported in the literature. they are considered to be heavier analogues of carbene. in earlier times, they were called silene, but this is a mistake, as that term means compounds of Ï-bonded silicon: si=c. the generic term analogous to carbene is "silicene." silylenes have been proposed as reactive intermediates and are so unstable that they usually cannot be isolated. while carbenes are observed in either the triplet or singlet state depending on the nature of the substituents, silylenes typically have a singlet ground state because the energy gap between the 3s and 3p orbitals of the silicon atom is very large and so the singlet-triplet gaps are enormous. ==history== the first experimental chemical observation of silylene as an intermediate was demonstrated by p.s. skell and e.j. goldstein in 1964. the first stable silylene was synthesized and isolated as a diamino silylene, n,nâ-di-tert-butyl-1,3-diaza-2-silacyclopent-4-en-2-ylidene, in 1994 by m. denk et al.denk, m., green, j.c., metzler, n., wagner, m. (1994), electronic structure of a stable silylene: photoelectron spectra and calculations. journal of the chemical society, dalton transactions, 2405â2410. ==synthesis and properties== silylenes are generally synthesized by thermolysis or photolysis of polysilanes, by silicon atom reactions (insertion, addition or abstraction), by pyrolysis of silanes, or by reduction of 1,1-dihalosilane. simple silylenes are very reactive species and easily dimerize to give disilenes, so their lifetime is very short. bulky substituents are used to prevent this dimerization and stabilize silylenes effectively
Inorganic_silicon_compounds Reactive_intermediates