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 1H‐ and 13C‐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.