Sterically hindered co-ordination sites in metal complexes. Part 1. The synthesis and properties of ‘capped’ four-co-ordinate metal Schiff-base complexes

Abstract

The synthesis of several sterically hindered N₂O₂ and N₄ ligands is described in which a quadridentate Schiff base is ‘capped’ by condensation of salicylaldehyde or pyrrole-2-carbaldehyde with a series of bis(8-aminonaphthyl) n-alkyl diethers. A number of representative complexes have been prepared and characterized with the metal ions Fe^II, Co^II, Ni^II, Cu^II, and Zn^II. The n.m.r. spectrum of the neutral monomeric nickel(II) derivative is consistent with the proposed trans planar ‘capped’ structure, a structure designed to provide for a study of the steric requirements of bonding to hindered metal-ion sites.