April 12, 2021
Need to add a trifluoromethyl group? I’m your reagent.
What molecule am I?

Trifluoromethyltrimethylsilane (TMSCF3) is a fluorinated derivative of tetramethylsilane (TMS), the Molecule of the Week for March 29, 2021. Like TMS, TMSCF3 is a volatile liquid; but the fluorinated compound is considerably more reactive and hazardous.

TMSCF3 is not synthesized from TMS; rather, it is formed by coupling molecules containing trifluoromethyl and trimethylsilyl groups. The initial synthesis, by Ingo Ruppert*, Klaus Schlich, and Wolfgang Volbach at the University of Bonn (Germany) in 1984, involved the reaction of trifluoromethyl bromide (CF3Br) and trimethylsilyl chloride (TMSCl) in the presence of an amine–phosphorus catalyst.

Similar methods followed over the next several years, culminating in one reported by G. K. Surya Prakash*, Ramesh Krishnamurti, and George A. Olah*1 at the University of Southern California (Los Angeles) in 1989 that does not require ozone-depleting reagents such as CF3Br. Instead, the researchers treated fluoroform (CHF3) with TMSCl and the base potassium hexamethyldisilazide to obtain TMSCF3 in 80% isolated yield.

Ruppert and Prakash prepared TMSCF3 because they had bigger things in mind. Specifically, they sought to introduce a reagent that could easily add the trifluoromethyl group to a wide range of organic substrates. Now known as the Ruppert–Prakash reagent, TMSCF3 has been used to add CF3 or the difluoromethylene group to aldehydes, ketones, olefins, alkynes, heterocyclic systems, and more.

In 2014, Mang Wang, Qun Liu, and colleagues at Northeast Normal University (Changchun, China) published an excellent review of TMSCF3 chemistry. So much work is being done with TMSCF3 that, even after the conclusion of the review, the authors felt compelled to add an additional section that reported findings that appeared after the original manuscript was submitted for publication.

1. Olah received the Nobel Prize in Chemistry in 1994 for his work on superacids and carbocations.

Trifluoromethyltrimethylsilane hazard information

Hazard class* Hazard statement
Flammable liquids, category 2 H225—Highly flammable liquid and vapor Chemical Safety Warning
Substances and mixtures which, in contact with water, emit flammable gases, category 2 H261—In contact with water, releases flammable gas Chemical Safety Warning
Acute toxicity, oral, category 4 H302—Harmful if swallowed Chemical Safety Warning
Skin corrosion/irritation, category 2 H315—Causes skin irritation Chemical Safety Warning
Serious eye damage/eye irritation, category 2A H319—Causes serious eye irritation Chemical Safety Warning
Specific target organ toxicity, single exposure, respiratory tract irritation, category 3 H335—May cause respiratory irritation Chemical Safety Warning

*Globally Harmonized System of Classification and Labeling of Chemicals.  
Explanation of pictograms.

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fast facts

CAS Reg. No. 81290-20-2
Silane, trimethyl-(trifluoromethyl)-
Empirical formula C4H9F3Si
Molar mass 142.20 g/mol
Appearance Colorless liquid
Boiling point 54–55 ºC
Water solubility Slight decomposition
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