Metal complexes of salicylhydroxamic acid and O-acetylsalicylhydroxamic acid

The salicylhydroxamic acid (H(2)Sha) complexes, Ni(HSha)(2) . 2H(2)O, Cu(HSha)(2) . 2H(2)O, Zn(HSha)(2) . 1.5H(2)O and Fe(Sha)(3) . 2H(2)O, in which the ligand is coordinated to the metal through the hydroxamate group have been synthesised. Acetylation of salicylhydroxamic acid with acetyl chloride in pyridine gave O-acetylsalicylhydroxamic acid (H(2)Sha-OAc) in which the hydroxamate oxygen is acetylated and from which the complexes Ni(HSha-OAc)(2) . H2O and Zn(Sha-OAc) were prepared. In the zinc complex the ligand is coordinated to the metal through the phenolate oxygen and the deprotonated nitrogen of the acetylhydroxamic group, the latter being an extremely rare type of coordination in the case of this metal ion. Attempted preparation of iron(III) and copper(II) complexes resulted in deacetylation of the ligand and the formation of salicylhydroxamate complexes. (C) 1997 Elsevier Science S.A.