Binuclear complexes of copper(II) and zinc(II) halides with bidentate and quadridentate Schiff base complexes

Abstract

Binuclear complexes of the types CuB,CuCl₂, CuB,ZnCl₂, ZnB,ZnCl₂, and CuL₂,CuCl₂ have been obtained where BH₂ is a quadridentate Schiff base derived from salicylaldehyde and a polyrnethylenediamine and LH is an N-alkylsalicylaldimine. The stereochemistry of the copper atoms in the binuclear complexes is inferred from comparisons of their reflectance spectra with the spectra of the simple copper complexes CuB and CuL₂. The structures of the zinc complexes are discussed by reference to near ultraviolet spectra of the ligands and infrared spectra in the 1500-1560 cm^-1 region. The evidence suggests that in the complexes of the type MB,M'Cl₂ either but not both metal atoms may approach a tetrahedral environment. The chemistry of the complexes ZnB,ZnCl₂ is complicated by the possibility of either or both zinc atoms becoming 5 coordinate by addition of solvent molecules; in some of these complexes the zinc chloride appears to be attached to a solvent molecule in a 5-coordinate Schiff base unit, rather than by bridging through phenolic oxygen atoms. The oomplexes CuL₂,CuCl₂ apparently have a symmetrical binuclear structure based on a trans arrangement of the Schiff base units rather than an unsymmetrical structure resembling that of the complexes CuB,CuCl₂. Complexes of the types CuL₂,ZnCl₂ and ZnL₂,ZnCl₂ could not be obtained.