A density functional study of ethylene rearrangements assisted by tungsten calix[4]arenes

Density functional calculations have been performed on all complexes involved in the rearrangements undergone by ethylene on the calix[4]arene tungsten fragment. [{p-But-calix[4](O)4}W(?2-C2H4)], which is the starting reactant of the rearrangement process, has been carefully investigated. In order to reduce the computational effort a simplified model of tungsten calix[4]arene has been considered. Preliminary calculations have shown that four vinylate groups reproduce adequately the geometrical, electronic, and bonding parameters of the calix[4]arene ligand so that we have employed the {(C2H3O)4}W fragment to investigate the ethylene rearrangements. Calculated geometrical and thermodynamical data obtained for ethylene rearrangements agree with the experimental X-ray data and the observed reaction trend.