Exo ‐ und endo ‐Tricarbonyleisenkomplexe von bicyclischen 2,3‐Dimethylidenverbindungen

Exo ‐ and endo ‐Tricarbonyliron Complexes of Bicyclic 2,3‐Dimethylidene Compounds. The preparation of exo ‐ and endo ‐tricarbonyliron complexes ( exo ‐ and endo ‐ 5 , ‐6 , ‐8 , and 9 ) of 2,3‐dimethylidene‐5‐bicyclo[2.2.1]heptene( 1 ), ‐bicyclo[2.2.1]‐heptane ( 2 ), ‐5‐bicyclo[2.2.2]octene ( 3 ) and ‐bicyclo[2.2.2]octane ( 4 ) is described. The complexes are obtained by thermal reaction of the bicyclic butadienes with di‐ironenneacarbonyl in hexane solution. exo ‐ and endo ‐ 5 are also formed photochemically from ironpentacarbonyl and 1 in pentane solution at −35°. The structural assignment of exo ‐ and endo ‐5 and ‐6 is based on their mass‐spectra and on coordination shifts in 1 H‐ and 13 C‐NMR.‐spectra exo ‐ and endo ‐6 are correlated with exo ‐ and endo ‐5 , respectively, by hydrogenation. Hydrogenation of the uncomplexed double bond in exo ‐ and endo ‐5 occurs in both complexes from the exo side as shown by deuteration experiments. The free ligand 1 reacts in the same stereospecific manner.