COPPER(II), NICKEL(II) AND COBALT(II) COMPLEXES WITH N,N′-BIS(2-N,N-DIMETHYLAMINOETHYL)PYRIDINE-2,6-DICARBOXAMIDE 1-OXIDE. BINUCLEATING BEHAVIOUR BY A DEPROTONATED PYRIDINE N-OXIDE LIGAND

Abstract

New copper(II), nickel(II), and cobalt(II) complexes are described with the potentially binu-cleating pyridine N-oxide ligand N,N′-bis(2-N,N-dimethylaminoethyl)pyridine-2,6-dicarboxamide 1-oxide (medpco). Electronic spectra and X-ray powder diffraction measurements indicate that metal complexes of the type M(medpco)Hal₂(H₂O) _x (Hal = Cl, Br) are five-coordinate. Monomeric structures are proposed with ONN-bonded ligand and coordinated halide. This is analogous to the coordination to one of the coppers in the previously reported X-ray structure of Cu₂(medpco)Cl₄. Complexes of the type M′₂(medpco-2H)Hal₂(H₂O) _z (M′ = Ni, Co), involving deprotonated ligand, are reported. These appear to have N-oxide-bridged structures, involving binucleating ligand, analogous to the previously reported X-ray structure of Cu₂(medpco-2H)Cl₂. Variable temperature magnetic data for the complexes are discussed.

Key Words:

• Pyridine N-oxide complexes
• N-oxide bridging
• binucleating ligand
• nickel(II)
• cobalt(II)