Silylene is a chemical compound with the formula SiH2. It is the silicon analog of methylene, the simplest carbene. Silylene is a stable molecule as a gas but rapidly reacts in a bimolecular manner[clarification needed] when condensed. Unlike carbenes, which can exist in the singletortriplet state, silylene (and all of its derivatives) are singlets.
Silylenes are formal derivatives of silylene with its hydrogens replaced by other substituents.[2] Most examples feature amido (NR2) or alkyl/aryl groups.[3][4]
Silylenes have been proposed as reactive intermediates. They are carbene analogs.[5]
Silylenes are generally synthesized by thermolysisorphotolysisofpolysilanes, by silicon atom reactions (insertion, addition or abstraction), by pyrolysisofsilanes, 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:
Early observations of silylenes involved generation of dimethylsilylene by dechlorination of dimethyldichlorosilane:[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 silyleneisN,N′-di-tert-butyl-1,3-diaza-2-silacyclopent-4-en-2-ylidene, first described in 1994 by Michael K. Denk et al.[7]
Synthesis of an isolable silylene.
The α-amido centers stabilize silylenes by π-donation. The dehalogenation of diorganosilicon dihalides is a widely exploited.[8]
^ abNagendran, Selvarajan; Roesky, Herbert W. (2008). "The Chemistry of Aluminum(I), Silicon(II), and Germanium(II)". Organometallics. 27 (4): 457–492. doi:10.1021/om7007869.
^Haaf, Michael; Schmedake, Thomas A.; West, Robert (2000). "Stable Silylenes". Accounts of Chemical Research. 33 (10): 704–714. doi:10.1021/ar950192g. PMID11041835.
^Gaspar, 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. ISBN0471967572.
^Skell, P. S.; Goldstein, E. J. (1964). "Dimethylsilene: CH3SiCH3". Journal of the American Chemical Society. 86 (7): 1442–1443. doi:10.1021/ja01061a040.
^Denk, 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.
^Driess, 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. PMID16866506.
^Moiseev, Andrey G.; Leigh, William J. (2006). "Diphenylsilylene". Journal of the American Chemical Society. 128 (45): 14442–14443. doi:10.1021/ja0653223. PMID17090011.
