Synthesis and structure of planar-chiral cyclopentadienyl–cobalt(I) complexes: three different chiralities in one molecule

Abstract

Diastereoisomerically pure planar-chiral cyclopentadienyl–cobalt complexes, 4 and 5, were prepared by the reaction of a trisubstituted cyclopentadiene bearing a (–)-menthyl group with [CoCl(PPh₃)₃] and acetylenes, and removal of the menthyl group from 4a and 5a afforded the optically pure enantiomers, (+)- and (–)-6, respectively; an X-ray structural analysis of 4a has revealed that there exist three different chiralities (planar, carbon-centred and helical) in one molecule.