Accelerated biphasic hydroformylation by vesicle formation of amphiphilic diphosphines

The synthesis, aggregation behavior, and catalytic activity of rhodium comp lexes of a series of Xantphos derivatives with surface-active pendant group s, -4-C6H4O(CH2)(n)C6H4(SO3Na)- (n = 0, 3, 6) is described. Electron micros copy experiments show that these ligands and their complexes form vesicles in water if the hydrophobic part of the ligand is large enough (n = 3, 6). The formed aggregates are stable at elevated temperatures (90 degrees C), a nd their presence lends to a significant enhancement of the solubility of o rganic substrates in aqueous solution. This enhanced solubility results dir ectly in a higher reaction rate in the rhodium-catalyzed hydroformylation o f 1-octene. Furthermore, recycling experiments show that the TOF and the hi gh selectivity toward the more valuable linear aldehyde remains approximate ly the same in four consecutive runs. This indicates that the aggregates st ay intact during the recycling and the active rhodium complex is retained i n the water-phase quantitatively.