Copper(II) complexes of o-hydroxyarylcarbonyl compounds

Abstract

A series of copper(11) complexes has been prepared of the type CuL₂Bn, where L is an o-hydroxy-aryl-, or naphthyl-, aldehyde, ketone, or ester, B is water or 4-methylpyridine, and n = 0, 1, or 2. All these complexes have a strong infrared band in the region 1600-1660 cm^-l, showing that the oxygen atoms in the chelate ring are non-equivalent ; their magnetic moments fall in the range usual for copper(11) compounds. Equilibrium constants determined for the addition of one molecule of 4-methylpyridine to the anhydrous compounds in chloroform solutions fall in the range 0.5 < k < 40 and are comparable to the constant for the addition of 4-methylpyridine to bis(acetylacetonato)copper(11) (b 2.7). Increased stability of the adducts can be associated with the inductive effects of ligand substituents. Ligand field spectra in the solid state and in solution closely resemble those of corresponding bis(acetylaoetonato)copper(11) complexes and provide evidence for square-planar structures of the anhydrous complexes and square-pyramidal structures of the 1 : 1 adducts with 4-methylpyridine or water. No evidence is available for the structures of 1 : 2 adduots which may be formed in solutions in 4-methylpyridine; these solutions are unstable, but the nature of the slow reactions which occur in these solutions is not known.