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

Abstract

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.