Photochemical Hydroformylation of Olefins with Cobalt Catalysts. 2. Ionic Cobalt Carbonyls

Article abstract of DOI:10.1021/ja00415a030

In the presence of CO/H2 or CO, H2, and P(n-Bu)3 a methanol solution of cobalt acetate is photochemically reduced to low-valent cobalt carbonyls, which are active catalysts for the hydroformylation of olefins.The hydroformylation of cyclohexene with Co2(CO)8 in methanol is enhanced by UV irradiation, probably via activation of the tetracarbonyl cobaltate ion (2) which is formed during the reaction.Similarly in the presence of excess phosphine the complex (<1><2>), which at 80 deg C and 80 bar synthesis gas pressure is completely inactive toward hydroformylation, is photochemically converted to HCo(CO)3P(n-Bu)3 (4). 4 is a very selective catalyst for the formation of n-aldehydes from α-olefins.Linear oxo products (99percent and 90percent) are obtained from propene and octene-1, respectively.In situ IR and UV spectroscopy shows that 4 is mainly produced by photolysis of the cation 1, and to a lesser extend via photolysis of 2.