In organic chemistry, triflate ( systematic name: trifluoromethanesulfonate), is a functional group with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

and

structure A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

. The triflate group is often represented by , as opposed to −Tf, which is the triflyl group, . For example, ''n''-butyl triflate can be written as . The corresponding triflate anion, , is an extremely stable polyatomic ion; this comes from the fact that triflic acid () is a

superacid In chemistry, a superacid (according to the classical 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.e. it is more acidic than pure

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...

, already one of the strongest

acid In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...

s known.

Applications

A triflate group is an excellent leaving group used in certain organic reactions such as nucleophilic substitution,

Suzuki coupling The Suzuki reaction is an organic reaction, classified as a cross-coupling reaction, where the coupling partners are a boronic acid and an organohalide and the catalyst is a palladium(0) complex. It was first published in 1979 by Akira Suzuki, a ...

s and Heck reactions. Since alkyl triflates are extremely reactive in S_N2 reactions, they must be stored in conditions free of

nucleophile In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...

s (such as water). The anion owes its stability to resonance stabilization which causes the negative charge to be spread symmetrically over the three oxygen atoms. An additional stabilization is achieved by the trifluoromethyl group, which acts as a strong

electron-withdrawing group In chemistry, an electron-withdrawing group (EWG) is a substituent that has some of the following kinetic and thermodynamic implications: *with regards to electron transfer, electron-withdrawing groups enhance the oxidizing power tendency of the ...

using the sulfur atom as a bridge. Triflates have also been applied as ligands for group 11 and 13 metals along with

lanthanide The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and yttr ...

s. Lithium triflates are used in some lithium ion batteries as a component of the

electrolyte An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dis ...

. A mild triflating reagent is phenyl triflimide or ''N'',''N''-bis(trifluoromethanesulfonyl)aniline, where the by-product is F₃SO₂N−Phsup>−.

Triflate salts

Triflate salts are thermally very stable with melting points up to 350 °C for sodium,

boron Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...

and silver salts especially in water-free form. They can be obtained directly from triflic acid and the metal hydroxide or metal carbonate in water. Alternatively, they can be obtained from reacting metal chlorides with neat triflic acid or

silver triflate Silver trifluoromethanesulfonate, or silver triflate is the triflate (CF3SO3−) salt of Ag+. It is a white or colorless solid that is soluble in water and some organic solvents including, benzene. It is a reagent used in the synthesis of organ ...

, or from reacting

barium triflate Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. The ...

with metal sulfates in water: :MCl_\mathit + \mathit HOTf -> M(OTf)_\mathit + \mathit HCl :MCl_\mathit + \mathit AgOTf -> M(OTf)_\mathit + \mathit AgCl (v) :M(SO4)_\mathit + \mathit Ba(OTf)2 -> M(OTf)_ + \mathit BaSO4 v Metal triflates are used as

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...

catalysts in organic chemistry. Especially useful are the

lanthanide triflates Lanthanide triflates are triflate salts of the lanthanides. These salts have been investigated for application in organic synthesis as Lewis acid catalysts. These catalysts function similarly to aluminium chloride or ferric chloride, but are stable ...

of the type (where Ln is a lanthanoid). A related popular catalyst scandium triflate is used in such reactions as aldol reactions and

Diels–Alder reaction In organic chemistry, the Diels–Alder reaction is a chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene derivative. It is the prototypical example of a peric ...

s. An example is the Mukaiyama aldol addition reaction between

benzaldehyde Benzaldehyde (C6H5CHO) is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. It is a colorless liquid with a characteristic almond-like odor. ...

and the silyl enol ether of

cyclohexanone Cyclohexanone is the organic compound with the formula (CH2)5CO. The molecule consists of six-carbon cyclic molecule with a ketone functional group. This colorless oily liquid has an odor reminiscent of acetone. Over time, samples of cyclohexan ...

with an 81% chemical yield. The corresponding reaction with the yttrium salt fails: Triflate is a commonly used weakly coordinating anion.

References

{{reflist Sulfonic acids Leaving groups Anions Trifluoromethyl compounds

Applications

Triflate salts

See also

References