Complexes of Di-2-pyridyl ketone. I. Complexes of first-row transition elements in normal oxidation states

Abstract

All the complexes of di-2-pyridyl ketone (DPK) described appear to involve N,N-chelation of the ligand. In CU(DPK)₂SO₄,2H₂O the water molecules are added across the ketone groups yielding gem-dihydroxy functions. Several previously reported solvated DPK-cupric complexes which were assigned N,O-chelated structures probably have analogous N,N-chelated structures with solvent molecules (H₂O or alcohols) added across the ketone group. The compounds M(DPK)₂Cl₂ (M = Mn^II, Fe^II, Co^II, Ni^II) are tentatively assigned cis-octahedral structures, and a number of mono- and bis-DPK-cupric complexes appear to have the common tetragonal or square-planar geometries. The compounds of stoicheiometry Co(DPK)₂(OH)2Cl,½H₂O and CO(DPK)₂(OH)₂NO₃, prepared from the corresponding cobalt(11) salts, are cobalt(111) derivatives in which one or both of the DPK units is reduced and probably acts as a tridentate ligand.