Silylation
Silylation is the introduction of a (usually) substituted silyl group (R3Si) to a molecule.
Silylation of organic compounds
Alcohols, carboxylic acids, amines, thiols, phosphates can be derivatized by silylation. The process involves the replacement of a proton with an trialkylsilyl group, typically trimethylsilyl (-SiMe3). A general technique is to deprotonate the substrate with a suitable strong base (e.g. butyl lithium), and allow it to react with a silyl chloride (e.g. trimethylsilyl chloride). A base is usually used to remove the hydrogen chloride formed:
- RXH + Base → [ HBase+][RX−]
- [HBase+][RX−] + R'3SiCl → RX-SiR'3 + [HBase+][Cl−]
Silyl derivatives are generally less polar and more volatile and more thermally stable than their precursor organic compound. The introduction of a silyl group(s) gives derivatives of enhanced volatility, making the derivatives suitable for analysis by gas chromatography and electron-impact mass spectrometry (EI-MS). For EI-MS, the silyl derivatives give more favorable diagnostic fragmentation patterns of use in structure investigations, or characteristic ions of use in trace analyses employing selected ion monitoring and related techniques.[1]
Similarly, silylation is used to introduce silyl ethers as protecting groups for organic synthesis.
Desilylation
Desilylation is the reverse of silylation: the silyl group is exchanged for a proton. Various fluoride salts (e.g. sodium, potassium, tetra-n-butylammonium fluorides) are popular for this purpose.
Silylation of metals
Coordination complexes with silyl ligands are well known. An early example is CpFe(CO)2Si(CH3)3. Metal silyl complexes are important intermediates in hydrosilation, a process used to make organosilicon compounds.[2]
See also
References
- ^ http://www.sigmaaldrich.com/analytical-chromatography/analytical-reagents/derivatization-reagents/silylation.html
- ^ Moris S. Eisen "Transition-metal silyl complexes" in The Chemistry of Organic Silicon Compounds. Volume 2 Edited by Zvi Rappoport and Yitzhak Apeloig, 1998 John Wiley & Sons. ISBN: 0-