Copper and palladium complexes with substituted pyrimidine-2-thiones and 2-thiouracils: syntheses, spectral characterization, and X-ray crystallographic study

Copper(I) and palladium(II) complexes containing 5-acetyl-6-methyl-1,2,3,4-tetrahydropyrimidine-2-thione (L1), ethyl 4,6-dimethyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate (L2), cis-5-acetyl-6-ethyl-5,6-dihydro-2-thiouracil (L3), and 5,6-dihydro-2-thiouracil (L4) have been synthesized. All complexes were characterized by elemental analysis, IR, 1H, and 13C NMR spectroscopy. To assign bands in the IR spectra of L1 and L2 and complexes with Cu(I) and Pd(II), deuterium substitution of movable protons at N-atoms was used. The crystal structures of two compounds, [Cu(L2)2Cl] and [Pd(L4)2Cl2], were determined by X-ray single-crystal and powder diffraction, respectively. In [Cu(L2)2Cl], copper has a rare coordination number of three and triangular surrounding of two neutral L2 molecules, coordinated through sulfurs, and chloride. In [Pd(L4)2Cl2], palladium has a standard square-planar geometry, formed by two uracil molecules and two chlorides. A new method for the synthesis of 5,6-dihydro-2-thiouracil, starting from β-aminopropionic acid, was suggested.