Aqueous biphasic hydroformylkation catalysed by protein-rhodium complexes

The water soluble complex deriving from Rh(CO)2(acac) and Human Serum Albumin (HSA) resulted efficient in the hydroformylation of several olefin substrates. The chemoselectivity and regioselectivity were generally higher with respect to those obtained by using the classic catalytic systems like TPPTS-Rh(I) (TPPTS = triphenylphosphine – 3,3’,3’’ - trisulfonic acid trisodiumsalt). Styrene and 1-octene, for instance, were converted in almost quantitative yield into the corresponding oxo-aldehydes at 60°C and 70 atm (CO/H2 = 1) even at very low Rh(CO)2(acac)/HSA catalyst concentrations. The possibility of easily recovering the Rh(I) compound makes the system environmentally friend. Circular dichroism technique was useful in demonstrating the Rh(I) binding to the protein and to give information on the stability in solution of the catalytic system. Some other proteins have been used to replace HSA complexing agent for Rh (I). The results were less impressive with respect to those obtained using HSA and their complexes with Rh(I) were much less stable.