Unexpected Coordination Behaviour of 3,5‐Di(2‐pyridyl)‐1,2,4‐oxadiazole

The coordination behaviour of 3,5‐di(2‐pyridyl)‐1,2,4‐oxadiazole ( L′ ) has been studied and compared with that of the 2,5‐di(2‐pyridyl)‐1,3,4‐chalcadiazoles L O , L S and L Se [ L O = 2,5‐di(2‐pyridyl)‐1,3,4‐oxadiazole, L S = 2,5‐di(2‐pyridyl)‐1,3,4‐thiadiazole, L Se = 2,5‐di(2‐pyridyl)‐1,3,4‐selenadiazole]. Ligand L′ and the new complexes [Cu II ( L′ ) 3 ](ClO 4 ) 2 · 1.5MeOH · H 2 O ( 1· 1.5MeOH · H 2 O), 1· MeCN, [Co II ( L′ ) 2 (MeOH) 2 ](ClO 4 ) 2 ( 2 ), [Co II ( L O ) 2 (MeOH) 2 ](ClO 4 ) 2 ( 3 ), [Cu II ( L′ ) 2 Cl 2 ] ( 4 ), [Cu II ( L′ ) 2 Br 2 ] ( 5 ) and [Cu II ( L Se ) 2 Cl 2 ] · MeOH ( 6· MeOH) have been structurally characterised by single‐crystal X‐ray diffraction analyses. With the help of DFT calculations and the analyses of metal–ligand bond lengths of similar complexes of L′ , L O , L S and L Se the binding capacities have been determined as L′  << L O  < L S  < L Se .