Bistriflimide, also known variously as bis(trifluoromethane)sulfonimide, bis(trifluoromethanesulfonyl)imide, bis(trifluoromethanesulfonyl)imidate (and variations thereof), informally and somewhat inaccurately as triflimide or triflimidate'','' or by the abbreviations TFSI or NTf₂, is a

non-coordinating anion Anions that interact weakly with cations are termed non-coordinating anions, although a more accurate term is weakly coordinating anion. Non-coordinating anions are useful in studying the reactivity of electrophilic cations. They are commonly foun ...

with the chemical formula Cfluorine">F₃sulfur">Soxygen">O₂)₂nitrogen">N">carbon.html" ;"title="carbon">Cfluorine">F₃sulfur">Soxygen">O₂)₂nitrogen">Nsup>−. Its salts are typically referred to as being metal triflimidates.

Applications

The anion is widely used in ionic liquids (such as trioctylmethylammonium bis(trifluoromethylsulfonyl)imide), since it is less toxic and more stable than more "traditional" counterions such as tetrafluoroborate. This anion is also of importance in lithium-ion and lithium metal batteries ( LiTFSI) because of its high dissociation and conductivity. It has the added advantage of suppressing crystallinity in poly(ethylene oxide), which increases the conductivity of that polymer below its melting point at 50 °C.

Bistriflimidic acid

The conjugate acid of bistriflimide, which is frequently referred to by the trivial name bistriflimidic acid (CAS: 82113-65-3), is a commercially available

superacid In chemistry, a superacid (according to the original definition) is an acid with an acidity greater than that of 100% pure sulfuric acid (), which has a Hammett acidity function (''H''0) of −12. According to the modern definition, a superacid i ...

. It is a crystalline compound, but is hygroscopic to the point of being

deliquescent Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water mol ...

. Owing to its very high acidity and good compatibility with organic solvents it has been employed as a catalyst in a wide range of chemical reactions. Its p''K''_a value in water cannot be accurately determined but in

acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not class ...

it has been estimated as −0.10 and in

1,2-dichloroethane The chemical compound 1,2-dichloroethane, commonly known as ethylene dichloride (EDC), is a chlorinated hydrocarbon. It is a colourless liquid with a chloroform-like odour. The most common use of 1,2-dichloroethane is in the production of vinyl ...

−12.3 (relative to the p''K''_a value of 2,4,6-trinitrophenol (

picric acid Picric acid is an organic compound with the formula (O2N)3C6H2OH. Its IUPAC name is 2,4,6-trinitrophenol (TNP). The name "picric" comes from (''pikros''), meaning "bitter", due to its bitter taste. It is one of the most acidic phenols. Like ot ...

), anchored to zero to crudely approximate the aqueous p''K''_a scale), making it more acidic than triflic acid (p''K''_a^MeCN = 0.70, p''K''_a^DCE(relative to

) = −11.4).

Naming

Developing an IUPAC name for bistriflimide that indicates the structure and reactivity is challenging, and changes to current names have been proposed. The main difficulty arises from the ambiguous use of the word ''

amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a chemical compound, compound with the general formula , where R, R', and R″ represent any group, typically organyl functional group, groups or hydrogen at ...

'' to mean an acylated (including sulfonylated) amine ''or'' the anionic form of an amine. Likewise, ''imide'' can refer to a bisacylated amine ''or'' a twice deprotonated amine. Thus, depending on the system used, there is ambiguity as to whether amide or imide is being used to refer to the parent acid or the anion. (The anion has been referred to as an ''amidate'' or ''imidate'' in an attempt to distinguish it from the acid.) The complications in naming these compounds was highlighted in an article by the IUPAC. Since then, the IUPAC has recommended (2013) that derivatives of anionic nitrogen can be named as

azanide Azanide is the IUPAC-sanctioned name for the anion . The term is obscure; derivatives of are almost invariably referred to as amides, despite the fact that amide also refers to the Organic chemistry, organic functional group –. The anion is t ...

s, so bis(trifluoromethanesulfonyl)azanide would be an acceptable and unambiguous name for the bistriflimide anion. The parent acid, whose trivial name is triflimidic acid, would then be called bis(trifluoromethanesulfonyl)azane. The name 1,1,1-trifluoro-''N''-((trifluoromethyl)sulfonyl)methanesulfonamide is also an unambiguous IUPAC-acceptable name, though the symmetry of the molecule is not apparent from this construction.

References

{{Reflist Non-coordinating anions Sulfonamides Superacids Trifluoromethyl compounds

Applications

Bistriflimidic acid

Naming

See also

References