First titanium square fragment {Ti4(μ4-Se)(μ2-Se2)4} in its selenoiodide: Synthesis and structure of Ti4Se9I6

The first titanium selenoiodide Ti4Se9I6 was synthesized as black crystals by heating of Ti, Se, and I2 at 250 °C in 5:9:5 M ratio. The crystal structure of the compound was solved by X-ray single-crystal diffractometry (sp. gr. P-1, a = 7.9652(10), b = 10.3390(15), c = 15.692(2) A; α = 79.116(7)°, β = 75.861(7)°, γ = 71.437(7)°; Z = 2) with final R1 = 0.0397. The structure includes square {Ti4(μ4-Se)(μ2-Se2)4} fragment coordinated by four terminal and four bridging μ2-I atoms. Ti4+ has d0 configuration, and stability of the structure fragments is provided by metal to ligand bonding which was confirmed by DFT calculations.