Khosro Mohammadi

Some new cobalt(III) complexes described as [Co(Chel)(PBu3)]ClO4 × H2O where (Chel) is the deprotonated form of a series of symmetric and unsymmetrical Schiff base ligands containing 3,4-diaminobenzophenone (3,4-DABP) and substituted salicylaldehyde moieties and [Co(Chel)(PMePh2)]ClO4 × H2O where (Chel) is [N’-(5-BrSalDABP)] were synthesized and characterized by 1H NMR, IR, UV–Vis spectroscopy, and elemental analysis. The formation constants and the thermodynamic parameters were determined spectrophotometrically for 1: 1 adduct formation of the new complexes as acceptor with some aliphatic amines such as benzylamine, n-butylamine, sec-butylamine and tertbutylamine as donors in DMSO solvent in constant ionic strength (I = 0.1 M NaClO4). The formation constants change according to the following trend due to the steric and the electronic factors of the cobalt(III) complexes: N’-5-OMe > N’-5-H > N’-5-Br > N’-5-Cl; N,N’-3-OMe > N,N’-4-Ome. The trend of the formation constants of cobalt(III) Schiff base complexes toward a given donor according to the axial ligand is as follow: PBu3 > PMePh2. Also, the following binding trend of the donors toward a given cobalt(III) Schiff base complex is obtained: benzylamine > n-butylamine > sec-butylamine > tert-butylamine.