Spectator cations and catalysis with sulfonated phosphines. The role of cations in determining reaction selectivity in the aqueous phase hydroformylation of olefins

Abstract

The hydroformylation of 1-hexene was carried out under two phase conditions with the water soluble catalyst, HRh(CO) (TPPTS) 3. The addition of different salts as a means to increase the solution ionic strength has a strong influence on reaction activity and selectivity. With monovalent cations the reaction activity decreases as ionic strength increases, while the selectivity, as measured by n b ratios, increases as the solution ionic strength increases. The size and the charge on the cation also influence the selectivity. For example the cations Li +, Na +, Cs + have a positive influence on reaction selectivity compared to catalysts without additional salt. In contrast Al 3+ has a negative influence on the reaction selectivity. It is proposed that cations play a role in determining the coordination geometry of catalytic intermediates which contributes to the diverse influence on reaction selectivity.