Directed semi-hydrogenation of triple bonds in diene tricarbonyliron complexes

Catalytic hydrogenation of a triple bond in P-position to the diene tricarbonyliron moiety, using palladium on carbon as catalyst, surprisingly stopped at the olefinic stage and the corresponding olefins were obtained. This protective effect seemed independent of many factors: the stereochemistry (E,E or E,Z) of the organometallic unit, the configuration and the nature of the vicinal functionality as well as of the substitution of the triple bond, particularly its electrophilicity.