TOWARDS CATALYTIC SELECTIVE DIMERIZATION OF OLEFINS OR REACTION RELATED TO HYDROFORMYLATION - CO-2(CO)(8) VERSUS RHCL(PPH(3))(3)

Dicobaltoctacarbonyl, Co-2(CO)(8), in pyridine and under syngas pressu re, catalyses the direct and selective dimerisation of aromatic olefin s to the corresponding saturated hydrocarbons. Under similar condition s, chlorotris( triphenyl) phosphine rhodium, RhCl(PPh(3))(3), promotes the selective reductive coupling of intermediate aldehydes C-n+1 (res ulting of an initial hydroformylation of the starting olefins C-n) int o new saturated monoaldehydes C-2n+2. The outcome of these reactions i s markedly influenced by the reaction conditions and by the structure of the starting olefins. Pyridine is essential as a solvent. A tentati ve mechanistic proposal is discussed for both reactions.