Basic research in aqueous organometallic hydroformylation ligands and catalysts

4 Basic research in aqueous organometallic hydroformylation ligands and catalysts 

In the preceeding two sections aqueous hydroformylation was mostly discussed in the context of industrial processes. It is, of course, impossible to categorize investigations as purely industrial and purely academic since the driving force behind the studies of a practically so important chemical transformation such as hydroformylation, ultimately arises from industrial needs. Nevertheless, several research projects have been closely associated with the developmental work in industry, while others explore the feasibility of new ideas without such connections. 

The reaction of [RhCl(COD)2] and four equivalents of P(CH2OH)3 in THF gave c s-[RhH2 P(CH2OH)3 4], which actively catalyzed the biphasic hydroformylation of 1-pentene [74], In a water/benzene mixture, at 100 °C and 40 bar syngas this substrate was quantitatively converted to hexanal (43 % yield) and 2-methylpentanal (57 %) in 20 h. At the [substrate]/[catalyst] ratio of 90 this is equivalent to a minimum TOF of 4.5 If1. The catalyst was recycled in the aqueous phase three times with no changes in its activity or selectivity. 

In the quest for suitable solvent systems the [Rh(CO)2(SULPHOS)] complex (SULPHOS = 31) was found to catalyze the hydroformylation of 1-hexene in water-methanol/isooctane (1/1/1, v/v/v) yielding heptanal and 2-methylhexanol in a ratio of 2.2 (80 °C, 30 bar syngas) [83], An important point here is in that the biphasic micture becomes homogeneous above 60 °C, but phase separation occurs again upon cooling to room temperature. This kind of solvent behaviour may lead to fast reactions at higher 

---