SYNTHESIS OF BICYCLIC PENTAALKYLCYCLOPENTADIENES AND THEIR METAL-COMPLEXES - CRYSTAL-STRUCTURE OF BIS-(1,2,3-TRIMETHYLBICYCLO[4.3.0]NONADIENYL) IRON

A new synthetic route to the bicylic pentaalkylcyclopentadienes 1,2,3-trimethylbicyclo[4.3.0]-nonadiene (NDH) and 1,2,3-trimethylbicyclo[10.3.0] pentadecadiene (PDDH) is reported. These ligands react directly and in good yields with Fe(CO)5, Mo(CO)6, Cr(CO)6 and RhCl3.xH2O to form dimeric peralkylcyclopentadienyl complexes, but can also, after deprotonation with (n)BuLi and further treatment with TiCl3 or FeCl2, be converted to the complexes (ND)2TiCl2, (PDD)2TiCl2 and (ND)2Fe. (ND)2Fe was characterized by a crystal-structure analysis. The complex surprisingly exhibits an ecliptical conformation of the five-membered rings, in which the relative orientation of the anellated six-membered rings deviates by 72-degrees from the ideally eclipsed conformation.