SYNTHESIS, CRYSTAL-STRUCTURES AND ELECTROCHEMICAL PROPERTIES OF CU-IIAND NI-II COMPLEXES WITH HEXADENTATE LIGANDS CONTAINING THIOETHER-AMIDOPYRIDYL DONOR SET

Novel two acyclic hexadentate ligands, o-(pyridine-2-carboxamidophenyl )]-1,4-dithiobutane (H(2)bpctb) and -(pyridine-2-carboxamidophenyl)]-1 ,5-dithiopentane (H(2)bpctp), containing thioether functions were synt hesized and their copper(II) and nickel(II) complexes [(Cu(bpctb)], 1: [Cu(bpctp)], 2; [Ni(bpctb)], 3 and [Ni(bpctp)], 4) were prepared. The structures of 1-4 were determined by X-ray crystallography. The coord ination geometries of 3 and 4 are octahedral with two amido and two py ridyl nitrogen atoms and two thioether sulfur atoms of hexadentate lig and. However, the coordination geometry of 2 is a flattened tetrahedro n combining two amido nitrogen atoms and two pyridyl nitrogen atoms of hexadentate ligand without thioether coordination. X-ray crystallogra phy and ESR spectroscopic studies revealed that the coordination geome try of 1 is an uncommon equatorially elongated octahedron in solid sta te. However, this coordination geometry changes to an axially elongate d one in solution. The copper(II/I) redox processes for 1 and 2 are ar ound -1.2 V and the nickel(II/III) processes for 3 and 4 at around 0.3 V vs ferrocene/ferrocenium couple were observed in DMSO. (C) 1998 Els evier Science Ltd. All rights reserved.