Phosphane-Based Cyclodextrins as Mass Transfer Agents and Ligands for Aqueous Organometallic Catalysis

Abstract

The replacement of hazardous solvents and the utilization of catalytic processes are two key points of the green chemistry movement, so aqueous organometallic catalytic processes are of great interest in this context. Nevertheless, these processes require not only the use of water-soluble ligands such as phosphanes to solubilise the transition metals in water, but also the use of mass transfer agents to increase the solubility of organic substrates in water. In this context, phosphanes based on a cyclodextrin skeleton are an interesting alternative since these compounds can simultaneously act as mass transfer agents and as coordinating species towards transition metals. For twenty years, various cyclodextrin-functionalized phosphanes have been described in the literature. Nevertheless, while their coordinating properties towards transition metals and their catalytic properties were fully detailed, their mass transfer agent properties were much less discussed. As these mass transfer agent properties are directly linked to the availability of the cyclodextrin cavity, the aim of this review is to demonstrate that the nature of the reaction solvent and the nature of the linker between cyclodextrin and phosphorous moieties can deeply influence the recognition properties. In addition, the impact on the catalytic activity will be also discussed.

Recoverable and recyclable water-soluble sulphonated salicylaldimine Rh(i) complexes for 1-octene hydroformylation in aqueous biphasic media

“…[4][5][6][7][8][9][10][11][12] This technique has been used widely including applications in various olefin transformation reactions. [13][14][15][16][17][18][19][20][21][22][23][24] Fig. 1 shows an illustration of the aqueous biphasic hydroformylation of 1-octene.…”

Rhodium-Catalyzed Aqueous Biphasic Olefin Hydroformylation Promoted by Amphiphilic Cyclodextrins

“…3 Aldehyde selectivity-(moles of aldehydes)/(moles of converted olefins) × 100. 4 Experiment conducted using aqueous phase of Experiment 10 (first recycling). 5 Experiment conducted using the aqueous phase of Experiment 16 (second recycling).…”

“…These include analytical chemistry, agriculture, pharmaceuticals, foods, toilet products, and catalysis [3]. In the field of aqueous biphasic organometallic catalysis, CDs have mainly been employed as platforms for the production of water-soluble ligands using transition metals [4][5][6][7][8][9][10][11][12][13]. They have also been used as mass-transfer agents in order to increase the solubility of hydrophobic substrates in water [14,15].…”

Cavity-shaped ligands for asymmetric metal catalysis

“…Catalysts with bulky aromatic ligands such as mesitylene bound to the metal tend to perform better in terms of enantioselectivity than less sterically crowded benzene analogs albeit with reduced activity (Scheme 17). Numerous examples of phosphorus containing CDs have been used as transition metal ligands for asymmetric catalytic reactions, usually associated with P(III) ligands [43,44], such as the hydrogenation and hydroformylation of prochiral alkenes, but also more recently the more challenging asymmetric gold(I)-catalyzed cycloisomerization reactions. Unlike the previous systems, these catalysts do not rely on the supramolecular properties of the CD host for effective enantiodiscrimination but on the ability of the phosphorus donor atom to direct the metal center in such a way that it can interact sterically with the chiral cavity.…”