Cerium(III) Trifluoromethanesulfonate
   HOME

TheInfoList



OR:

Lanthanide triflates are triflate salts of the
lanthanide The lanthanide () or lanthanoid () series of chemical elements comprises at least the 14 metallic chemical elements with atomic numbers 57–70, from lanthanum through ytterbium. In the periodic table, they fill the 4f orbitals. Lutetium (el ...
s. These salts have been investigated for application in
organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...
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 ...
catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...
s. These catalysts function similarly to
aluminium chloride Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms a hexahydrate with the formula , containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are col ...
or
ferric chloride Iron(III) chloride describes the inorganic compounds with the formula (H2O)x. Also called ferric chloride, these compounds are some of the most important and commonplace compounds of iron. They are available both in anhydrous and in hydrated f ...
, but they are water-tolerant (stable in water). Commonly written as Ln(OTf)3·(H2O)9 the nine waters are bound to the lanthanide, and the triflates are counteranions, so more accurately lanthanide triflate nonahydrate is written as n(H2O)9OTf)3.


Synthesis

Lanthanide triflates are synthesized from lanthanide oxide and aqueous triflic acid: ::Ln2O3 + 6HOTf + 18H2O → 2 n(H2O)9OTf)3 + 3H2O Anhydrous lanthanide triflates can be produced by dehydrating their hydrated counterparts by heating between 180 and 200 °C under reduced pressure: : n(H2O)9OTf)3 → Ln(OTf)3 + 9H2O


Example reactions


Friedel-Crafts reactions

Lanthanide triflates are proposed for Friedel-Crafts acylations and alkylations, which are often carried out with AlCl3 as the catalyst in an organic solvent. The nature of the Friedel-Craft reaction, especially the acylation, forces the AlCl3 to irreversibly complex with any oxygen-containing group in the product, with the only way of decomplexing it being to destroy the AlCl3 part with water altogether. An estimated 0.9 kg of AlCl3 is wasted per kilogram of typical product- it is hydrolysed into Al2O3 and the extremely corrosive HCl. In contrast, lanthanide triflates' complexes with the product are easily separated by water, and the lanthanide triflate hydrate thus formed can be simply heated to boil the water away (This does not work for aluminium chloride due to loss of HCl; same goes for the lanthanide chlorides, hence the necessity of the triflate counterion). This avoids the need to use organic solvents- one can just use water as the solvent. Ln(OTf)3 catalysts are used for
esterification In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...
s.


Other C-C bond-forming reactions

La(OTf)3 catalysts have been used for Diels-Alder, aldol, and
allyl In organic chemistry, an allyl group is a substituent with the structural formula . It consists of a methylene bridge () attached to a vinyl group (). The name is derived from the scientific name for garlic, . In 1844, Theodor Wertheim isolated a ...
ation reactions.Engberts, J., Feringa, B., Keller, E. & Otto, S. 1996, “Lewis-acid Catalysis of Carbon Carbon Bond Forming Reactions in Water”, Recuil des Travaux Chimiques des Pays-Bas 115(11-12), 457-464 Some reactions require a mixed solvent, such as aqueous
formaldehyde Formaldehyde ( , ) (systematic name methanal) is an organic compound with the chemical formula and structure , more precisely . The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde. It is stored as ...
, although Kobayashi et al. have developed alternative surfactant-water systems.
Michael addition In organic chemistry, the Michael reaction or Michael 1,4 addition is a reaction between a Michael donor (an enolate or other nucleophile) and a Michael acceptor (usually an α,β-unsaturated carbonyl) to produce a Michael adduct by creating a c ...
s are another very important industrial method for creating new carbon-carbon bonds, often with particular functional groups attached. Addition reactions are inherently atom efficient, so are preferred synthesis pathways. La(OTf)3 catalysts not only enable these reactions to be carried out in water, but can also achieve
asymmetric catalysis Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of Chirality (chemistry), chirality are formed ...
, yielding a desired
enantio-specific In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities which are mirror images of each other and non-superpos ...
or diastereo-specific product.


C-N bond-forming reactions

Lanthanide triflates can be used to synthesize pyridine by catalysing either the condensation of aldehydes and amines, or the aza Diels-Alder reaction catalytic synthesis. Again, water can be used as a solvent, and high yields can be achieved under mild conditions.
Nitro compounds In organic chemistry, nitro compounds are organic compounds that contain one or more nitro functional groups (). The nitro group is one of the most common explosophores (functional group that makes a compound explosive) used globally. The nitr ...
are common in pharmaceuticals,
explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An ex ...
s,
dye Juan de Guillebon, better known by his stage name DyE, is a French musician. He is known for the music video of the single "Fantasy Fantasy is a genre of speculative fiction that involves supernatural or Magic (supernatural), magical ele ...
s, and
plastics Plastics are a wide range of synthetic or semisynthetic materials composed primarily of polymers. Their defining characteristic, plasticity, allows them to be molded, extruded, or pressed into a diverse range of solid forms. This adaptab ...
. As for carbon compounds, catalysed Michael additions and
aldol reaction The aldol reaction (aldol addition) is a Chemical reaction, reaction in organic chemistry that combines two Carbonyl group, carbonyl compounds (e.g. aldehydes or ketones) to form a new β-hydroxy carbonyl compound. Its simplest form might invol ...
s can be used. For aromatic nitro compounds, synthesis is via a
substitution reaction A substitution reaction (also known as single displacement reaction or single substitution reaction) is a chemical reaction during which one functional group in a chemical compound is replaced by another functional group. Substitution reactions ar ...
. The standard synthesis is carried out in a solution of
nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...
, mixed with excess
sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
to create
nitronium The nitronium ion, , is a cation. It is an onium ion because its nitrogen atom has +1 charge, similar to ammonium ion . It is created by the removal of an electron from the paramagnetic nitrogen dioxide molecule A molecule is a grou ...
ions. These are then substituted on to the aromatic species. Often, the para-isomer is the desired product, but standard systems have poor selectivity. As for acylation, the reaction is normally quenched with water, and creates copious acidic waste. Using a La(OTf)3 catalyst in place of sulfuric acid reduces this waste considerably. Clark et al. report 90% conversion using just 1 mol% of ytterbium triflate in weak nitric acid, generating only a small volume of acidic waste.


Green catalysts

Lanthanide triflates are stable in water, so avoid the need for organic solvents, and can be recovered for reuse. on their catalytic effect in water, the range of researched applications for La(OTf)3 catalysts has exploded. Waller, F.J.; Barrett. A.G.M.; Braddock, D.C.; Ramprasad, D. "Lanthanide (III) Triflates as Recyclable Catalysts for Atom Economic Aromatic Nitration." Chem. Commun. 1997, 613-614.


See also

* Scandium(III) trifluoromethanesulfonate


References

{{reflist Triflates Acid catalysts Lanthanide compounds