Département de chimie moléculaire

We report a mol. dynamics study of propene/water biphasic systems involved in the hydroformylation of propene catalyzed by water sol. rhodium complexes with TPPTS3- ligands (where TPPTS3- is the tris(m-sulfonatophenyl)phosphine ligand, neutralized by Na+ counterions). The neat biphasic system is found to display a quite thin and irregular interface, involving some propene partitioning to the bulk aq. phase. Interestingly, when propene is dild. (at low pressures), propene mols. tend to somewhat condense at the interface. The most important finding concerns the interfacial activity of key reaction partners (the free TPPTS3- ligands, the active catalyst [RhH(CO)(TPPTS)2]6-, and the reaction intermediate [RhH(CO)(TPPTS)2(propene)]6-). This is found first by following the outcome of the phase sepn. of randomly mixed water/propene solns. with these different solutes, and further supported by potential of mean force (PMF) calcns. on the migration of the [RhH(CO)(TPPTS)2(propene)]6- complex across the interface. Added butyraldehyde mols. (the product of the reaction) are shown to increase the surface activity the [RhH(CO)(TPPTS)2(propene)]6- complex, due to increased attractions of the complex with the org. phase. These results point to the importance of the aq. interface in the multiphasic catalyzed reaction, and suggest that a significant amt. of propene reacts "right at the interface", i.e., in a region of less than 1 nm width of the soln. [on SciFinder(R)]