Characterization of the O-centered vanadium selenoiodides V4OSe8I6·X (X = I2, 3,5-dimethylpyrazole)

O-centered tetranuclear vanadium selenoiodide complex [V4OSe8I6] forms at the reaction of the elements with the addition of water, and may utilize inorganic (I2) or organic (3,5-dimethylpyrazole) molecules for packing in crystalline state. X-ray structural analysis, XPS and IR spectroscopy revealed structural and spectral identity of the complex in these two compounds. TG analysis showed that the V4OSe8I6·I2 compound is more resistant to thermolysis than V4OSe8I6·dmp due to the difference in system of intermolecular contacts. [Display omitted] •O-centered tetranuclear complex V4OSe8I6 is formed at reaction of V, Se, I2, H2O and 3,5-dimethylpyrazole.•Compounds V4OSe8I6·I2 and V4OSe8I6·dmp were examined by XPS and IR spectroscopy.•Two compounds containing complex V4OSe8I6 were revealed to have different thermal behavior. O-centered vanadium(IV) selenoiodide V4OSe8I6·3,5-dimethylpyrazole was synthesized in a sealed glass ampoule at moderate temperature 220 °C from the mixture of V, Se, I2, small quantity of water and 3,5-dimethylpyrazole. The X-ray single crystal structure of the compound was solved. The crystal structure includes O-centered tetranuclear complex [V4(μ4-O)(μ-Se2)4(μ-I)2I4] in which vanadium atoms are bridged by diselenide (Se2)2– and iodide I– groups; four terminal iodides coordinate vanadium atoms additionally. Molecules of 3,5-dimethylpyrazole form non-covalent contacts with iodine and selenium atoms of the V4OSe8I6 complexes. Once compounds V4OSe8I6·3,5-dimethylpyrazole and V4OSe8I6·I2 contain similar electroneutral coordination molecular fragment V4OSe8I6, we present here a discussion of spectroscopic properties as well as thermal behavior. Comparing XPS data, both compounds contain vanadium complexes with major V 2p binding energies very similar to each other, and almost equal binding energies in XPS Se 3d and I 3d showing their forms of (Se2–)2 and I–, respectively. Thermolysis character of these compounds revealed higher stability of V4OSe8I6·I2 than V4OSe8I6·3,5-dimethylpyrazole, that indicates a greater stability of the system of non-covalent contacts involving iodine molecules than 3,5-dimethylpyrazole.