Hydroformylation proton-active

Whatever metal is used, homogeneous processes suffer from high cost resulting from the consumption of the catalyst, whether recycled or not. This is why two-phase catalytic processes have been developed such as hydroformylation catalyzed by rhodium complexes, which are dissolved in water thanks to hydrophilic phosphines (cf. Section 3.1.1.1) [17]. Due to the sensitivity of most dimerization catalysts to proton-active or coordinating solvents, the use of non-aqueous ionic liquids (NAILs) as catalyst solvents has been proposed. These media are typically mixtures of quaternary ammonium or phosphonium salts, such as 1,3-dialkylimi-dazolium chloride, with aluminum trichloride (cf. Section 3.1.1.2.2). They prove to be superb solvents for cationic active species such as the cationic nickel complexes which are the active species of olefin dimerization [18, 19]. The dimers. 

Scheme 1.14 Generation of an active hydroformylation catalyst by protonation of [CoCCO) ]" with the cation of an ionic liquid.

The vinylidene cluster Fe3Rh(CO)ji(C = CH(Ph)), which was prepared by Mathieu and coworkers started from a trinuclear Fe cluster by reaction with [RhCl(CO)2]2 in the presence of TIBF and subsequent protonation, which exhibited the same activity in the hydroformylation of 1-pentene as Rh (CO)j 2 (Scheme 1.63) [16,17]. 

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