Alkoxy and Phenoxy Bridged Dimeric Copper(II) Complexes with Salicylaldimine Ligands

The tridentate SchifF base N-3-hydroxy-n-propylsalicylaldimine can be coordinated with copper(II) to form three kinds of dimeric oxy-bridged antiferromagnetic complexes (metal: ligand ratio—1: 1), as well as the normal monomeric complex. In one of the dimeric complexes pairs of copper atoms are bridged by pairs of the deprotonated alcoholic oxygens of the ligands. The others have an extra ligand X (X=–Cl, –ONO2) per copper atom, the metals are bridged by phenolic oxygens, the alcoholic hydroxyls are not deprotonated, but are either coordinated (if X=Cl) to five-coordinated copper atoms in discrete dimer molecules, or participate in intermolecular hydrogen bonding linking individual dimeric molecules in which the copper atoms are four-coordinated. In the presence of pyridine, ammonia, or mild inorganic base, a rearrangement reaction can be induced, resulting in conversion of the phenolic-bridged (five-coordinated copper) dimer into the related alcoholic-bridged (fourcoordinated copper) dimer. This behaviour is not followed by N-hydroxyethylsalicylaldimine which appears to form only one kind of copper complex [Cu(Lig)X] (X=–C1, –ONO2); in which the metal atoms are essentially planar and do not take part in strong antiferromagnetic interactions.