A 14-membered macrocyclic Schiff base derived from 3-salicylideneacetylacetone and o-phenylenediamine acts as a tctradentate and strongly conjugated ligand to form a cationic solid complex with CuC12. U.v.-vis. and e.s.r. spectral data reveal a strong ligand to metal 7z-interaction in the square planar complex. C.v. data reveal that the title ligand is able to stabilize the copper(III) oxidation state more cffectivcly than comparable saturated or partially unsaturated macrocyclic ligands and confers a weaker tendency for reduction of copper(II) to copper(I) and copper(0). While the inclusion of a PPh 3 ligand suppresses the Cu ~ -, Cu j -, Cu u oxidation, imidazole and pyridinc strongly enhance the Cu ~I ~ Cu ~II oxidation ofthc complex.

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Several bis/tris-salicylaldehyde, salicylaldimine and salicyalethylenediimine chelates of cobalt(III), ehromium(III), cobalt(IX), nickel(II) and copper(II) readily react with various brominating agents and undergo a-bromo/cyano/ succinimido substitution, with or without accompanying bromine substitution of the aryl ring. The selectivity of these reactions on the metal-coordinated salicylaldehyde derivatives allows the preparation in 50-80% yield of hitherto unreported specific a-bromo products. The substituted organic compounds could be isolated by demetallation of the chelate products.