Silanone

The general structure of a silanone

A silanone in chemistry is the silicon analogue of an ketone. The general description for this class of organic compounds is R1R2Si=O with silicon connected to a terminal oxygen atom via a double bond and also with two organic residues (R).[1] Silanones are extremely reactive [1] and until 2013 have only been detected by argon matrix isolation [2][3] or in the gas phase [4] but not isolated. A synthesis of a stable silanone was reported in 2014. Silanones are of some interest to academic research.

Silanones are unstable and favor oligomerisation to a siloxane. The reason for this instability is the weak pi bond with a small HOMO–LUMO energy gap caused by an unfavorable overlap between the p-orbitals of silicon and oxygen. A second reason for the observed instability is the strongly polarized Sið+ - Oð− bond.[1]

A stable silanone was reported in 2014.[5] In this compound silicon is bonded to a SIDipp group (1,3-bis(2,6-iPr2-C6H3)imidazolidin-2-ylidene) and a (Cp*)Cr(CO)3 group. Its stability is owed to the direct coordination of silicon to chromium and to steric shielding. The reported Si=O bond length is 1.526 Angstrom and in line with expectation. It has been described as a cationic metallosilanone.[1]

History

The first to postulate a silanone were Kipping & Lloyd in 1901 [6] but their products were in fact siloxanes. Silanones are of some relevance to the double bond rule.

References

  1. 1 2 3 4 Sen, S. S. (2014), A Stable Silanone with a Three-Coordinate Silicon Atom: A Century-Long Wait is Over. Angew. Chem. Int. Ed., 53: 8820–8822. doi:10.1002/anie.201404793
  2. ↑ On the proposed thermal interconversion of matrix-isolated dimethylsilylene and 1-methylsilene: their reactions with oxygen atom donors Charles A. Arrington, Robert West, Josef Michl J. Am. Chem. Soc., 1983, 105 (19), pp 6176–6177 doi:10.1021/ja00357a048
  3. ↑ Infrared spectroscopic evidence for silicon-oxygen double bonds: silanone and the silanoic and silicic acid molecules Robert Withnall, Lester Andrews J. Am. Chem. Soc., 1985, 107 (8), pp 2567–2568 doi:10.1021/ja00294a070
  4. ↑ M. Bogey; B. Delcroix; A. Walters; J-C Guillemin (1996). "Experimentally Determined Structure of H2SiO by Rotational Spectroscopy and Isotopic Substitution". J. Mol. Spectrosc. 175 (2): 421–428. Bibcode:1996JMoSp.175..421B. doi:10.1006/jmsp.1996.0048.
  5. ↑ Filippou, A. C., Baars, B., Chernov, O., Lebedev, Y. N. and Schnakenburg, G. (2014), Silicon–Oxygen Double Bonds: A Stable Silanone with a Trigonal-Planar Coordinated Silicon Center. Angew. Chem. Int. Ed., 53: 565–570. doi:10.1002/anie.201308433
  6. ↑ XLVII.—Organic derivatives of silicon. Triphenylsilicol and alkyloxysilicon chlorides F. Stanley Kipping, Ph.D., D.Sc., F.R.S. and Lorenzo L. Lloyd J. Chem. Soc., Trans., 1901,79, 449-459 doi:10.1039/CT9017900449
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