Synthesis and coordination chemistry of 4 `,4 ``-disubstituted 2,2 `: 6 `,2 ``: 6 ``,2 ```-quaterpyridines and crystal and molecular structures of nickel(II) and cobalt(II) complexes

A range of symmetrical 4′,4″-disubstituted 2,2′:6′,2″:6″,2‴-quaterpyridines has been prepared and their coordination behaviour with metal ions having a preference for tetrahedral and octahedral geometries has been studied. The new ligands reacted with copper(I) and silver(I) salts to form dinuclear double-helical complexes; reaction with nickel(II) or cobalt(II) salts gave mononuclear species. The crystal structures of three mononuclear complexes are reported and demonstrate that the ligand binds in a tetradentate mode to the equatorial plane of the octahedral metal centre.