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 Ni^II and Co^II salts were studied. New Ni^II and Co^III 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. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2666–2678, December, 2005.