Stereoselective synthesis of chiral pinene[5,6]bipyridine ligands and their coordination chemistry

The C-2-symmetric chiral pinene[5,6]bipyridine V (Chart 1) was synthesized according to a procedure published by our group recently (Kolp, B.; Abeln, D.; Stoeckli-Evans, H.; Zelewsky, A. v. Eur. J. Inorg. Chem. 2001, 1207). A series of stereoselectively alkylated derivatives (Va-Vo) (Table 1) was pr epared. The solid-state structures of the compounds Vc and Vk were determin ed by single-crystal X-ray diffraction, where both compounds show a transoi d conformation of the bipyridine unit and proved to be alkylated stereosele ctively from the sterically less hindered side of the pinene moiety. The X- ray structure of the cobalt complex 4 shows the metal ion to be tetrahedral ly coordinated by one chiral bipyridine V and two chloride ligands. If 2 eq uiv of ligand V was used, 2:1 complexes were obtained with Cu(I), Ag(I), an d Co(II) ions.