New complex compounds of palladium (II) with biologically active ligand 2 - ethyl - 6 methyl - 3 - hydroxy-pyridine - mexidol in acidic medium (pH = 5,3) of the following composition have been synthesized – (C8H12O⊕N)2 [PdCl4]. In this case, the ligand is protonated and as a single-charged cation occupies an external coordination sphere. The structure of the complex is proved by X-ray structure analysis. It is shown that the structure is constructed of an isolated complex anion [PdCl4]2- and cation C8H12O⊕N. The square planar coordination of the palladium atom is formed from three chlorine atoms and the formed tetraacidoanion ligand forms a hydrogen bond. The average length of Pd-Cl bond is 2, 3030 Α°, there are no deviations from 900 valence angles of Cl-Pd-Cl. The palladium atom is not shifted from the plane coordination polyhedron (square) and therefore trance angles of Cl-Pd-Cl are 1800. Two different lengths -2,289 Α° and 2,713 Α° of hydrogen bonds are related to the geometric location of the ligand functional group. The obtained 2 – ethyl – 6 – methyl – 3 -hydroxypyridinetrachloro - palladium - mexidazole was tested for radioprotective properties. Toxicity of the preparation is LD50 - 240 mg/kg of animal weight. Toxicological studies of mexidazole in mice, rats and dogs did not reveal cardiotoxic, immunotoxic, embryonic, nephrotoxic, hematoxic and other types of side effects. Mexidazole is removed from the body with urine 5-8 hours after intravenous injection. The carried out biological test showed that the compound, along with radioprotective properties, has some antitumor activity.

The interaction of dithiodiethylamine (cystamine) (L1) with platinum compounds in non-aqueous and aqueous media has been studied. It was shown that in aqueous solutions the disulfide bond L1 cleaves with the subsequent coordination of platinum of the resulting β-mercaptoethylamine (mercamine, LH). Depending on the reaction conditions, binuclear complexes of the composition [Рt2(LН)2С14] with bridging chlorine or sulfur atoms or [Рt2L2С12] with bridging chlorine atoms are formed. An X-ray structural analysis of the complex [Рt2(LН)2С14] (I) was carried out. Crystals of I are rhombic, at 20°С а = 17.283(1), b = 9.987(1), с = 8.0187(9) Å; R = 0.030. Molecule I is a binuclear complex in which platinum atoms are linked by a pair of bridging thiolate ligands (-SСН2-СН2-МН3+). The Рt2S2 metal cycle is bent along the sulfur-sulfur line, so that the dihedral angle between the coordination planes of platinum atoms is 138 °. The S-S distance, equal to 2.909 (1) Å, is noticeably shorter than the double van der Waals radius of the sulfur atom (3.60 Å). Carrying out the reaction in benzene makes it possible to obtain the complex (L1Н2)[РtХ4] (X = С1, Вг) with the retention of the sulfur-sulfur bond in the ligand. The structure of the complexes is confirmed by the data of IR spectroscopy.

The trinuclear complexes with simple and mixed ligands of platinum (II) with mercaptoethanol and mercaptoethylamine have been generated and their contents and structures investigated by numerous physicochemical methods. Mercaptoethanol (SHCH2CH2OH) is coordinated monodentally with just sulfur atom and forms pentacyclic metalchelate ring, where as mercaptoethylamine (HSCH2CH2NH2) is coordinated monodentally as well as bidentally and forms an identical ring (pentacyclic metalchelate). The sulfur atom of ligands plays a bridge role between the metals in the trinuclear platinum complexes. The hydroxyl group of mercaptoethanol does not participate in the coordination

New complex compounds of palladium (II) with biologically active ligand 2 - ethyl - 6 methyl - 3 - hydroxy-pyridine - mexidol in acidic medium (pH = 5,3) of the following composition have been synthesized – . In this case, the ligand is protonated and as a single-charged cation occupies an external coordination sphere. The structure of the complex is proved by X-ray structure analysis. It is shown that the structure is constructed of an isolated complex anion – and cation . The square planar coordination of the palladium atom is formed from three chlorine atoms and the formed tetraacidoanion ligand forms a hydrogen bond. The average length of Pd-Cl bond is 2, 3030 , there are no deviations from 900 valence angles of Cl-Pd-Cl. The palladium atom is not shifted from the plane coordination polyhedron (square) and therefore trance angles of Cl-Pd-Cl are 1800. Two different lengths -2,289 and 2,713 of hydrogen bonds are related to the geometric location of the ligand functional group. The obtained 2 – ethyl – 6 – methyl – 3 -hydroxypyridinetrachloro - palladium - mexidazole was tested for radioprotective properties. Toxicity of the preparation is LD50 - 240 mg/kg of animal weight. Toxicological studies of mexidazole in mice, rats and dogs did not reveal cardiotoxic, immunotoxic, embryonic, nephrotoxic, hematoxic and other types of side effects. Mexidazole is removed from the body with urine 5-8 hours after intravenous injection. The carried out biological test showed that the compound, along with radioprotective properties, has some antitumor activity.