New O‐centered titanium chalcohalide: synthesis and structure of Ti 4 O(Se 2 ) 4 Br 6

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

The first vanadium selenoiodide V₄O(Se₂)₄I₆·I₂ was synthesized at a moderate temperature of 220 °C from V, Se, I₂, and water. Its crystal structure (tetragonal space group P4₂/nbc, a = 11.838(1) Å, c = 18.689(1) Å) contains O-centered vanadium(IV) tetranuclear fragment [V₄(μ₄-O)(μ₂-Se₂)₄(μ₂-I)₂I₄], where the edges of the distorted tetrahedron V₄ are bridged by four diselenide (Se₂)^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 V₄O(Se₂)₄I₆·I₂ 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.