SPECTATOR CATIONS AND CATALYSIS WITH SULFONATED PHOSPHINES - THE ROLEOF CATIONS IN DETERMINING REACTION SELECTIVITY IN THE AQUEOUS-PHASE HYDROFORMYLATION OF OLEFINS

The hydroformylation of l-hexene was carried out under two phase condi tions with the water soluble catalyst, HRh(CO) (TPPTS)(3). The additio n of different salts as a means to increase the solution ionic strengt h has a strong influence on reaction activity and selectivity. With mo novalent cations the reaction activity decreases as ionic strength inc reases, 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+, N a+, Cs+ have a positive influence on reaction selectivity compared to catalysts without additional salt. In contrast Al3+ has a negative inf luence on the reaction selectivity. It is proposed that cations play a role in determining the coordination geometry of catalytic intermedia tes which contributes to the diverse influence on reaction selectivity .