Coordination chemistry of 5,5 ''-disubstituted 2,2 ': 6 ',2 ''-terpyridines

Two 2,2':6',2"-terpyridine ligands bearing substituents in the 5 and 5"-pos itions have been prepared and their iron(II) complexes studied to investiga te the influence of substituents in these positions. A synergistic interpla y between sigma- and pi-bonding effects, involving conjugation of the subst ituents with the central ring, means that, in contrast to 4'-substituted 2, 2':6',2"-terpyridines, the metal-ligand interactions cannot be simply corre lated with the electron-donor or -acceptor properties of the substituents. The crystal structure of the complex [Fe(3)(2)][PF6](2). 2MeCN (3 = 5,5"-bi s(propoxy)-2,2':6',2"-terpyridine) is reported. In addition, cobalt(II) and ruthenium(II) complexes of 5,5"-bis(propoxy)-2,2':6',2"-terpyridin were pr epared and characterised. (C) 1998 Elsevier Science Ltd. All rights reserve d.