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Silylene is a chemical compound with the formula SiR2. It is the silicon analog of carbene. Silylene rapidly when condensed.

Silylenes are formal derivatives of silylene with its hydrogens replaced by other substituents.cite-ref-2[2] Most examples feature amido (NR2) or organyl groups.cite-ref-hr-3-0[3]cite-ref-denk1-4-0[4]

Silylenes have been proposed as reactive intermediates. They are carbene analogs.cite-ref-5[5]

• Synthesis and properties

• Related reactions

• See also

• References

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:

Si + Cl2 → SiCl2

SiCl2 + Cl2 → SiCl4

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:cite-ref-6[6]

SiCl2(CH3)2 + 2 K → Si(CH3)2 + 2 KCl

The formation of dimethylsilylene was demonstrated by conducting the dechlorination in the presence of trimethylsilane: the trapped product being pentamethyldisilane:

Si(CH3)2 + HSi(CH3)3 → (CH3)2Si(H)−Si(CH3)3

A room-temperature isolable N-heterocyclic silylene is N,N′-di-tert-butyl-1,3-diaza-2-silacyclopent-4-en-2-ylidene:cite-ref-7[7]

The α-amido centers stabilize silylenes by π-donation. The dehalogenation of diorganosilicon dihalides is a widely exploited.cite-ref-8[8]

In one study diphenylsilylene is generated by flash photolysis of a trisilane:cite-ref-9[9]

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 1.3×1010 mol−1 s−1 which is close to diffusion control.

• Carbene analogs

• N-heterocyclic silylene

• Silenes, R2Si=SiR2

• Silylium ions, protonated silylenes

cite-note-11. citerefiupac-chemical-nomenclature-and-structure-representation-division2013IUPAC Chemical Nomenclature and Structure Representation Division (2013). "P-71.2.2.1". In Favre, Henri A.; Powell, Warren H. (eds.). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. IUPAC–RSC. ISBN 978-0-85404-182-4.

cite-note-22. ↑ citerefmizuhatasasamoritokitoh2009Mizuhata, Yoshiyuki; Sasamori, Takahiro; Tokitoh, Norihiro (2009). "Stable Heavier Carbene Analogues". Chemical Reviews. 109 (8): 3479–3511. doi:10.1021/cr900093s. PMID 19630390.

cite-note-hr-33. ↑ citerefnagendranroesky2008Nagendran, Selvarajan; Roesky, Herbert W. (2008). "The Chemistry of Aluminum(I), Silicon(II), and Germanium(II)". Organometallics. 27 (4): 457–492. doi:10.1021/om7007869.

cite-note-denk1-44. ↑ citerefhaafschmedakewest2000Haaf, Michael; Schmedake, Thomas A.; West, Robert (2000). "Stable Silylenes". Accounts of Chemical Research. 33 (10): 704–714. doi:10.1021/ar950192g. PMID 11041835.

cite-note-55. ↑ citerefgasparwest1998Gaspar, Peter; West, R. (1998). "Silylenes". The Chemistry of Organic Silicon Compounds. The Chemistry of Functional Groups. Vol. 2. pp. 2463–2568. doi:10.1002/0470857250.ch43. ISBN 0471967572.

cite-note-66. ↑ citerefskellgoldstein1964Skell, P. S.; Goldstein, E. J. (1964). "Dimethylsilene: CH3SiCH3". Journal of the American Chemical Society. 86 (7): 1442–1443. doi:10.1021/ja01061a040.

cite-note-77. ↑ citerefdenklennonhayashiwest1994Denk, Michael; Lennon, Robert; Hayashi, Randy; West, Robert; Belyakov, Alexander V.; Verne, Hans P.; Haaland, Arne; Wagner, Matthias; Metzler, Nils (1994). "Synthesis and Structure of a Stable Silylene". Journal of the American Chemical Society. 116 (6): 2691–2692. doi:10.1021/ja00085a088.

cite-note-88. ↑ citerefdriessyaobrymvan-w-llen2006Driess, Matthias; Yao, Shenglai; Brym, Markus; Van Wüllen, Christoph; Lentz, Dieter (2006). "A New Type of N-Heterocyclic Silylene with Ambivalent Reactivity". Journal of the American Chemical Society. 128 (30): 9628–9629. doi:10.1021/ja062928i. PMID 16866506.

cite-note-99. ↑ citerefmoiseevleigh2006Moiseev, Andrey G.; Leigh, William J. (2006). "Diphenylsilylene". Journal of the American Chemical Society. 128 (45): 14442–14443. doi:10.1021/ja0653223. PMID 17090011.