Carbon dioxide induced phase switching for homogeneous-catalyst recycling.

SwitchPhos: Rhodium complexes formed from PPh(3) ligands functionalized with weakly basic amidine groups are highly active catalysts for the hydroformylation of alkenes. On bubbling with CO(2) in the presence of water, the yellow rhodium complexes move into the water phase, whereas bubbling with N(2) at 60 degrees C causes them to switch back into the organic phase. The catalysts can be used for reactions in water or an organic phase.