Vanadium O-Centered Selenoiodide Complex: Synthesis and Structure of V₄O(Se₂)₄I₆·I₂

Abstract

The first vanadium selenoiodide V 4 O(Se 2 ) 4 I 6 •I 2 was synthesized at a moderate temperature of 220 °C from V, Se, I 2 , and water. Its crystal structure (tetragonal space group P4 2 /nbc, a = 11.838(1) Å, c = 18.689(1) Åwhere the edges of the distorted tetrahedron V 4 are bridged by four diselenide (Se 2 ) 2− and two iodide ligands; four terminal iodides coordinate V atoms additionally. This type of complex is known for Ti, Nb, and Ta but is new for vanadium. Magnetic susceptibility measurements of V 4 O(Se 2 ) 4 I 6 •I 2 showed four unpaired electrons on vanadium atoms at room temperature and drop of the effective magnetic moment at cool down, presumably due to partial electron pairing. Probability of this transition to the diamagnetic state is in accord with the calculated electronic structure.

2d, or Not 2d: An Almost Perfect Mock of Symmetry

“…The experimental diffraction pattern of the product shown is a poor match with calculated patterns of both reagent phases and potential products (Figure 5; the crystal structures of M2, C and L are estimated in this work, one for M1 was taken from [33]). There are no observable peaks, which would correspond to reagents.…”

“…The representatives of this group are numerous minerals which structures are described in terms of different coordination of fragments {M 4 O} (M = Cu, Pb, Ln, Bi, Hg) bearing molecular (0D) or oligomeric structures as well as infinite coordination motifschains (1D), layers (2D), as well as framework structures (3D) [59]. On the other side, M2 and C, as well as a few of the related compounds [33,34], possess a more complex fragment, {M 4 O(Q 2 ) 4 } (Q 2 for dichalcogenide ligand), which can be considered as a structural building block. The similar building blocks are also observed in various oxochalcohalides of 3-6 period transition elements with molecular structure Ti 4 OS 8 Hal 6 (Hal = Cl [35], Br [36]), Ti 4 OSe 8 Br 6 [60], as well as with chain structure M 4 OTe 9 I 4 (M = Ti [37], Nb [38], Ta [39]).…”

“…Having obtained a small series of selenium-iodide vanadium complexes, we noticed that heating of similar ratios of starting species (most often metal vanadium, selenium, iodine and water as an oxygen source) at a temperature of 220 • C results in the formation of various molecular compounds containing an O-centered tetra-nuclear fragment V 4 OSe 8 I 6 [33,34]. In their crystal structures molecules V 4 OSe 8 I 6 form non-covalent contacts with iodine or 3,5-dimethylpyrazole molecules.…”

“…Our work on the search for vanadium chalcohalides for the first time revealed the conditions for the formation of an O-centered tetra-nuclear complex [V 4 O(µ-Se 2 ) 4 I 4 (µ-I) 2 ] 0d [33,34] (hereinafter nd superscript will denote the connectivity of the coordination fragments), which is arranged similarly to molecular titanium complexes [35,36]. There is a µ 4 -O connected V 4 -core in the shape of a distorted tetrahedron, which is additionally bridged by four diselenide (Se 2 ) 2− and two iodide ligands; four terminal iodides coordinate V atoms additionally.…”