Silylene is a chemical compound with the formula SiR<sub>2</sub> (R = H). It is the silicon analog of carbene. Silylenes decomposes rapidly when condensed.
Silylenes are formal derivatives of silylene with its hydrogens replaced by other substituents. Most examples feature amido (NR<sub>2</sub>) or organyl groups.
Silylenes have been proposed as reactive intermediates. They are carbene analogs.
Silylenes have been generated 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. It has long been assumed that the conversion of metallic Si to tetravalent silicon compounds proceeds via silylene intermediates:
Similar considerations apply to the direct process, the reaction of methyl chloride and bulk silicon.
Early observations of silylenes involved generation of dimethylsilylene by dechlorination of dimethyldichlorosilane:
The formation of dimethylsilylene was demonstrated by conducting the dechlorination in the presence of trimethylsilane: the trapped product being pentamethyldisilane:
A room-temperature isolable N-heterocyclic silylene is :
The ñ-amido centers stabilize silylenes by ÃÂ-donation. The dehalogenation of diorganosilicon dihalides is a widely exploited.
In one study diphenylsilylene is generated by flash photolysis of a trisilane:
In this reaction diphenylsilylene is extruded from the trisila ring. The silylene can be observed with UV spectroscopy at 520 nm and is short-lived with a chemical half-life of two microseconds. Added methanol acts as a chemical trap with a second order rate constant of which is close to diffusion control.