Trifluoroacetate ions, catalysis

Many types of palladacyclic complexes have been used as precursors to catalysts for a variety of coupling processes146,147. Mixtures of dimeric palladacycles containing bridging halide, acetate or trifluoroacetate ions and a phosphine or carbene ligand have been studied as catalysts for the animation of aryl halides. The isolated phosphine adducts can also be applied in catalysis. 

According to their miscibility with water, ionic liquids are also frequently classified as hydrophilic or hydrophobic. The hydrophilic ionic liquids are typically salts composed of halide, acetate, nitrate, trifluoroacetate, and, in some cases, tetrafluoroborate anions, in particular their salts with [AMIM] having short alkyl chains, as these ionic liquids are totally miscible with water. The ionic liquids composed of PF and (CF3S02)2N with [AMIM] are immiscible with water in bulk, and are therefore referred to as hydrophobic ionic liquids. The ionic liquids consisting of BF4 and CFsSOi" ions with [AMIM] can be totally miscible or immiscible depending on the substituents on the cation, and they are therefore sometimes called tunable ionic liquids (22). A recent review covers relevant properties of some ionic liquids for catalysis (42,43). 

Cleavage with an ensuing Heck reaction was developed by using the T1 triazene linker [51] (Scheme 6.1.20). On cleavage with trifluoroacetic acid a diazonium ion is first formed this can couple to an added alkene under the action of palladium catalysis. The coupling proceeds well with simple terminal alkenes, styrenes, and di- and even trisubstituted alkenes. The advantage of this process is clearly the possibility of using volatile alkenes (and alkynes) without contamination by any salt or other less volatile by-product, particularly with the use of palladium on charcoal as the catalyst. 

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