Disilene

Disilene
Identifiers
CAS Number	15435-77-5 ;
ChemSpider	123409 ;
PubChem CID	139934;
CompTox Dashboard (EPA)	DTXSID50165597 ;
Properties
Chemical formula	Si; 2H; 4
Molar mass	60.2028 g mol−1
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Disilene /daɪsaɪliːn/ (systematically named disilicon tetrahydride) is an inorganic compound with the chemical formula Si
₂H
₄. The name disilene, referring to the structure of a particular prototropic tautomer of the molecule. It is the simplest silene.

Properties and bonding

Disilene is a molecule with one Si=Si bond, and four equivalent Si-H bonds.

Unlike ethylene, disilene is kinetically unstable with respect to tautomerisation. Disilene has two other tautomers, that are very close in energy: (μ²-H)disilene, and disilanylidene.^[1]

Organodisilenes

Disilenes bearing sterically bulky substituents are isolable and have been well characterized although they remain mainly of academic interest. The first stabilised disilene was tetramesityldisilene, (C₆Me₃H₂)₄Si₂. The Si=Si distance in this molecule is 2.15 Å, about 10% shorter than a typical Si–Si single bond. The Si₂C₄ core is roughly planar.^[2] Such species are typically prepared by reduction of organosilicon halides: 2 R₂SiCl₂ + 4 Na → R₂Si=SiR₂ + 4 NaCl An alternative synthesis involves photolysis of trisilacyclopropanes. When the R group is not bulky, cyclic or polymeric polysilanes are the products.

In one study ^[3] a disilene is prepared by an intramolecular coupling of a 1,1-dibromosilane with potassium graphite. The silicon double bond in the resulting compound has a bond length of 227 picometer (second largest ever found) with trans-bent angles 33° and 31° (by X-ray diffraction).

Tricyclic Disilenes with Highly Strained Si-Si Double Bonds

In addition to this the substituents around the Si-Si bond are twisted by 43°. The disilene isomerizes to a tetracyclic compound by heating at 110°C in xylene thereby releasing its strain energy^{[clarification needed]}.

References

^ McCarthy, M. C.; Yu, Z.; Sari, L.; Schaefer, H. F.; Thaddeus, P. (15 February 2006). "Monobridged Si₂H₄". The Journal of Chemical Physics. 124 (7). USA: American Institute of Physics. doi:10.1063/1.2168150.
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
^ Fused Tricyclic Disilenes with Highly Strained Si-Si Double Bonds: Addition of a Si-Si Single Bond to a Si-Si Double Bond Ryoji Tanaka, Takeaki Iwamoto, and Mitsuo Kira Angewandte Chemie International Edition Volume 45, Issue 38 , Pages 6371 - 6373 2006 doi:10.1002/anie.200602214

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[1] McCarthy, M. C.; Yu, Z.; Sari, L.; Schaefer, H. F.; Thaddeus, P. (15 February 2006). "Monobridged Si₂H₄". The Journal of Chemical Physics. 124 (7). USA: American Institute of Physics. doi:10.1063/1.2168150.

[2] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

[3] Fused Tricyclic Disilenes with Highly Strained Si-Si Double Bonds: Addition of a Si-Si Single Bond to a Si-Si Double Bond Ryoji Tanaka, Takeaki Iwamoto, and Mitsuo Kira Angewandte Chemie International Edition Volume 45, Issue 38 , Pages 6371 - 6373 2006 doi:10.1002/anie.200602214

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