Chiral Induction in Self-Assembled Helicates: CHIRAGEN Type Ligands with Ferrocene Bridging Units

The aim of this work was the preparation of enantiomerically pure bis(pinene−bipyridine) ligands containing the
ferrocenyl moiety. Several such ligands (1−3) were synthesized and completely characterized. These molecules
can be diastereoselectively deprotonated at the acidic methylene group of the pinene moiety using a strong and
sterically hindered base such as LDA. Subsequent reaction of the formed anion with alkyl halides yield the family
of C2-symmetric enantiopure compounds (1a−c). Copper(I), silver(I), or zinc(II) complexes with several ligands
(C1−C8) were prepared and structurally characterized in the solid state and in solution. Self-assembled helical
species are formed in several cases. It became evident that the chiral groups present in the ligand do not completely
determined the helical configuration of the assemblages. Diastereoselectivity is thus not complete with this type of
ligands, contrary to other, similar ligands studied before.