Synthesis and molecular structures of novel seven-co-ordinated oxo- and nitrido-rhenium(<scp>V</scp>) complexes of 2,2′ : 6′,2″ : 6″,2‴-quaterpyridine

Reaction of [ReO2(PPh3)2I] and [ReNCl2(PPh3)2] with 2,2′ : 6′,2″ : 6″,2‴-quaterpyridine (L) in methanol gave [ReO(L)(OMe)2]ClO4 and [ReN(L)(PPh3)Cl]ClO4 respectively. The structures determined by X-ray crystallography revealed seven-co-ordination around rhenium with ReO and ReN distances of 1.666(4) and 1.647(6)A respectively. Intense metal-to-ligand charge-transfer transitions in the visible region and reversible ReVI–ReV redox couples have been observed for both complexes in acetonitrile.