Silylene

generic silylene
	Simplest silylene has R=Hydrogen
Names
	IUPAC name Silylene
	Systematic IUPAC name Silylidene
	Other names Hydrogen silicide(−II); Silicene
Identifiers
CAS Number	13825-90-6;
3D model (JSmol)	Interactive image;
ChemSpider	4885758 ;
PubChem CID	6327230;
CompTox Dashboard (EPA)	DTXSID70884652 ;
	InChI InChI=1S/H2Si/h1H2 Key: XMIJDTGORVPYLW-UHFFFAOYSA-N ;
	SMILES [SiH2];
Properties
Chemical formula	H2Si
Molar mass	30.101 g·mol−1
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

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.^[2] Most examples feature amido (NR₂) or organyl groups.^[3]^[4]

Silylenes have been proposed as reactive intermediates. They are carbene analogs.^[5]

Synthesis and properties

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:^[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:^[7]

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

Related reactions

Decamethylsilicocene is an example of a silylene.^[3]

In one study diphenylsilylene is generated by flash photolysis of a trisilane:^[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.

References

^ IUPAC 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.
^ Mizuhata, Yoshiyuki; Sasamori, Takahiro; Tokitoh, Norihiro (2009). "Stable Heavier Carbene Analogues". Chemical Reviews. 109 (8): 3479–3511. doi:10.1021/cr900093s. PMID 19630390.
^ ^a ^b Nagendran, 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. PMID 11041835.
^ 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. ISBN 0471967572.
^ 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. PMID 16866506.
^ Moiseev, Andrey G.; Leigh, William J. (2006). "Diphenylsilylene". Journal of the American Chemical Society. 128 (45): 14442–14443. doi:10.1021/ja0653223. PMID 17090011.

[1] IUPAC 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.

[2] Mizuhata, Yoshiyuki; Sasamori, Takahiro; Tokitoh, Norihiro (2009). "Stable Heavier Carbene Analogues". Chemical Reviews. 109 (8): 3479–3511. doi:10.1021/cr900093s. PMID 19630390.

[HR-3] Nagendran, Selvarajan; Roesky, Herbert W. (2008). "The Chemistry of Aluminum(I), Silicon(II), and Germanium(II)". Organometallics. 27 (4): 457–492. doi:10.1021/om7007869.

[denk1-4] Haaf, Michael; Schmedake, Thomas A.; West, Robert (2000). "Stable Silylenes". Accounts of Chemical Research. 33 (10): 704–714. doi:10.1021/ar950192g. PMID 11041835.

[5] 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. ISBN 0471967572.

[6] Skell, P. S.; Goldstein, E. J. (1964). "Dimethylsilene: CH₃SiCH₃". Journal of the American Chemical Society. 86 (7): 1442–1443. doi:10.1021/ja01061a040.

[7] 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.

[8] 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. PMID 16866506.

[9] Moiseev, Andrey G.; Leigh, William J. (2006). "Diphenylsilylene". Journal of the American Chemical Society. 128 (45): 14442–14443. doi:10.1021/ja0653223. PMID 17090011.

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Silylene

Synthesis and properties

Related reactions

See also

References

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