Département de chimie moléculaire

Using mol. dynamics (MD) simulations, we investigate the interfacial distribution of partners involved in the phase transfer rhodium catalyzed hydroformylation of olefins promoted by $\beta$-cyclodextrins ($\beta$-CDs). The $\beta$-CDs, the reactant (alkene), product (aldehyde), several rhodium complexes (the catalyst, its precursor, and its alkene adduct) are simulated at the water-"oil" interface, where oil is represented by chloroform or hexane. It is shown that unsubstituted $\beta$-CD and its 6-methylated and 2,6-dimethylated analogs adsorb at the interface, whereas the liposol. permethylated CD does not. The precursor of the catalyst [RhH(CO)(TPPTS)3]9- (with triphenylphosphine trisulfonated TPPTS3- ligands) sits in water, but the less charged [RhH(CO)(TPPTS)2]6- catalyst and the [RhH(CO)(TPPTS)2(alkene)]6- reaction intermediate are clearly surface active. The TPPTS3- anions also conc. at the interface, where they adopt an amphiphilic conformation, forming an elec. double layer with their Na+ counterions. Thus, the most important key partners involved in the hydroformylation reaction conc. at the interface, thereby facilitating the reaction, a process which may be further facilitated upon complexation by CDs. These results point to the importance of adsorption at the liq.-liq. interface in the two-phase hydroformylation reaction of olefins promoted by $\beta$-CDs and provide microscopic pictures of this peculiar region of the soln. [on SciFinder(R)]