Rhodium-Catalyzed Aqueous Biphasic Olefin Hydroformylation Promoted by Amphiphilic Cyclodextrins

Hydroformylation is an industrial process that allows for the production of aldehydes from alkenes using transition metals. The reaction can be carried out in water, and the catalyst may be recycled at the end of the reaction. The industrial application of rhodium-catalyzed aqueous hydroformylation has been demonstrated for smaller olefins (propene and butene). Unfortunately, larger olefins are weakly soluble in water, which results in very low catalytic activity. In an attempt to counteract this, we investigated the use of amphiphilic oleic succinyl-cyclodextrins (OS-CDs) synthesized from oleic acid derivatives and maleic anhydride. OS-CDs were found to increase the catalytic activity of rhodium during the hydroformylation of water-insoluble olefins, such as 1-decene and 1-hexadecene, by promoting mass transfer. Recyclability of the catalytic system was also evaluated in the presence of these cyclodextrins.

A dinuclear phosphite rhodium(I) complex obtained by syngas treatment of a Rh/hydroxy phosphonite olefin hydroformylation precatalyst

A hydroxy phosphonite was found to be unstable during the catalyst preformation routine applied towards a rhodium olefin hydroformylation catalyst. C—P bond cleavage occurred when the phosphonite was reacted with [(acac)Rh(1,5-COD)] (acac is acetyl acetate and 1,5-COD is cycloocta-1,5-diene) at 80 °C and 20 bar of CO/H2. As a result, a nearly planar six-membered ring structure consisting of two rhodium(I) cations and two bridging phosphorous acid diester anions was formed, namely bis[μ-(4,8-di-tert-butyl-2,10-dimethoxydibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]-1:2κ2 P:O;1:2κ2 O:P-bis{[6-([1,1′-biphenyl]-2-yloxy)-4,8-di-tert-butyl-2,10-dimethoxydibenzo[d,f][1,3,2]dioxaphosphepine-κP]carbonylrhodium(I)} toluene tetrasolvate, [Rh2(C22H28O5P)2(C34H37O5P)2(CO)2]·4C7H8. Further coordination of phosphite and of carbonyl groups resulted in 16-electron rhodium centres.