Fluorous catalysis

In the 15 years since its invention, fluorous (biphasic) catalysis has become a well-established area and provides a complementary approach to other variants of biphasic catalysis. Fluorous solvents are nontoxic and environmentally benign. Owing to their low surface tension, they do not form emulsions and due to their high density separate readily from other components in solvent mixtures. All these characteristics could make fluorous biphase catalysis superior to the analogous aqueous systems. Conversely, the same features that make fluorous solvents immiscible with many organic liquids make them bad solvents of organometallic catalysts, too, and chemical modifications of the catalysts (ligands) are required to attain sufficient solubility. Moreover, to retain the catalyst in the fluorous phase... 

In comparison with traditional biphasic catalysis using water, fluorous phases, or polar organic solvents, transition metal catalysis in ionic liquids represents a new and advanced way to combine the specific advantages of homogeneous and heterogeneous catalysis. In many applications, the use of a defined transition metal complex immobilized on a ionic liquid support has already shown its unique potential. Many more successful examples - mainly in fine chemical synthesis - can be expected in the future as our loiowledge of ionic liquids and their interactions with transition metal complexes increases. 

The use of thermomorphic systems has recently been studied as a way of achieving catalyst separation in homogeneous catalysis. For example, a biphasic hydroformylation catalyst system was developed to take advantage of the unusual solvent characteristics of perfluorocarbons combined with typical organic solvents (4). Fluorous/organic mixtures such as perfiuoromethylcyclohexane... 

Biphasic catalysis in an organic/fluorous solvent system by Pd/dendrimer nanocomposites. 

Various other biphasic solutions to the separation problem are considered in other chapters of this book, but an especially attractive alternative was introduced by Horvath and co-workers in 1994.[1] He coined the term catalysis in the fluorous biphase and the process uses the temperature dependent miscibility of fluorinated solvents (organic solvents in which most or all of the hydrogen atoms have been replaced by fluorine atoms) with normal organic solvents, to provide a possible answer to the biphasic hydroformylation of long-chain alkenes. At temperatures close to the operating temperature of many catalytic reactions (60-120°C), the fluorous and organic solvents mix, but at temperatures near ambient they phase separate cleanly. Since that time, many other reactions have been demonstrated under fluorous biphasic conditions and these form the basis of this chapter. The subject has been comprehensively reviewed, [2-6] so this chapter gives an overview and finishes with some process considerations. 

In comparison to traditional biphasic catalysis using water, fluorous phases or polar organic solvents, transition metal catalysis in ionic liquids represents a new and advanced way of combining the specific advantages of homogeneous and heterogeneous catalysis. 

Fluorous Catalysts and Fluorous Phase Catalyst Separation for Hydrogenation Catalysis... 

The first fluorous phosphine ligands for application in fluorous phase catalysis were fluorous trialkylphosphines 1 [7-9]. 

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