SYNTHESIS AND CHARACTERIZATION OF VANADYL(IV) COMPLEXES OF SCHIFF-BASES DERIVED FROM ANTHRANILIC ACID AND SALICYLALDEHYDE (OR ITS DERIVATIVES) OR ACETYLACETONE - SINGLE-CRYSTAL X-RAY STRUCTURES OF THE OXIDIZEDPRODUCTS

Anhydrous, dimeric vanadyl(IV) complexes of Schiff bases derived from [1+1] condensation of salicylaldehyde (or its derivatives) and anthran ilic acid, have been synthesized from CH3CN and were characterized by elemental analysis, FTIR, EPR, absorption, TGA, cyclic voltammetry and room temperature magnetic susceptibility measurements. These complexe s were found to be oxidized by air in polar solvents like MeOH and DMF to V-V products. The E(1/2) values were found to be around 660 mV ind icating that the carboxylate group favours vanadyl(IV) binding when co mpared to the alkoxo-bound vanadium complexes. Oxidative instability o f these complexes are dependent on the substituent on the salicylaldeh yde ring and follow an order, 5,6-benzo > H greater than or equal to 3 -OMe in MeOH and DMF. Attempted recrystallization of the dimeric vanad yl(IV) complex from pyridine led to products of oxidation, polymerizat ion and loss of Schiff base ligand. Single crystal X-ray diffraction s howed the oxidation product to be a decavanadate with the pyridinium c ounter cation, [C5NH6](6) V10O28 . 2H(2)O. When the dinuclear vanadyl( IV) complex was recrystallized from MeOH, it gave a product of mononuc lear carboxylate bound octahedral VO3+ moiety along with the presence of both MeOH and OMe units in the coordination sphere with a formula, VO(L)(OMe)(MeOH), where L = 1+1 Schiff base derived from 5,6-benzosali cylaldehyde and anthranilic acid, as studied through single crystal X- ray diffraction. Copyright (C) 1996 Elsevier Science Ltd