Complexation in a 5-acylpyrimidine-4-thione—aliphatic diamine—metal(II) chloride system (M = Ni or Co). The molecular structure of fac-tris(5-acetyl-2,4-dimethylpyrimidine-6-thiolato)cobalt(III)

The reactions of 5-acylpyrimidine-4-thiones with aliphatic diamines in the presence of NiII and CoII salts were studied. New NiII and CoIII complexes with ligands of the pyrimidinethione series were synthesized. The results of the reactions of 5-acetyl-6-methyl-2-phenylpyrimidine-4-thione and 5-acetyl-2,6-dimethylpyrimidine-4-thione with ethylenediamine or 1,3-diaminopropane in the presence of NiCl2· 6H2O or CoCl2·6H2O depend on (1) the nature of the substituent at position 2 of the pyrimidine ring, (2) the length of the polymethylene bridge between the nitrogen atoms in the diamine molecule, (3) the nature of complex-forming metal, and (4) the pyrimidinethione: diamine ratio. The resulting complexes were studied by electrochemical methods. The mechanism of electrooxidation and electro-reduction of 5-acylpyrimidine-2-thiones and related nickel and cobalt complexes was proposed. The structures of the complexes were investigated by NMR, UV-Vis spectroscopy, and IR spectroscopy and mass spectrometry. The molecular structure of fac-tris(5-acetyl-2,4-dimethylpyrimidine-6-thiolato)cobalt(III) was established by X-ray diffraction. According to semiempirical quantum-chemical calculations by the PM3(tm) method, both the highest occupied and lowest unoccupied molecular orbitals in the molecules of the compounds under study have a π symmetry and are localized predominantly on the ligand fragments.