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Abstract
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Some new Schiff bases derived from 3,4-diaminopyridine (3,4-DAP) and their new unsymmetrical Co(III)
five coordinate complexes described as [Co(Chel)(L)]ClO4H2O where (Chel) is the deprotonated form of a
series of unsymmetric ligands containing 3,4-diaminopyridine (3,4-DAP) and substituted salicylaldehyde
moieties and a new Co(III) six coordinate Co(III) complex, were synthesized and characterized by 1H NMR,
IR, UV–Vis, and elemental analysis. For the new synthesized five coordinate complexes, the formation
constants of the interaction of the Co(III) Schiff bases with various donors were measured spectrophotometrically.
The trend of the formation constants of the five coordinate Co(III) Schiff base complexes
toward a given phosphine is as follow: 5-H > 5-Br and the formation constants trend of these donors
are as follow: PBu3 > PPh2Me. Furthermore the adduct formation of the five coordinate [Co(3,4-Salpyr)(
PBu3)] ClO4H2O, with aromatic amines shows the following binding trend: Im > 2-MeIm > 2-
EtIm > BzIm. The trend of the formation constants of Co(III) Schiff base complexes toward a given donor
according to the phosphine axial ligand is as follow: PBu3 > PPh2Me.
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