New O‐centered titanium chalcohalide: synthesis and structure of Ti₄O(Se₂)₄Br₆

Abstract

Dedicated to Prof. Hansgeorg Schnöckel on the occasion of his 80th birthdayNew O-centered tetranuclear titanium complex Ti 4 O(Se 2 ) 4 Br 6 has been prepared from TiSe 1.73 , Se, SeO 2 and Br 2 at moderate temperature by ampule synthesis. Its X-ray crystal structure (monoclinic space group P2 1 /c, a = 9.4850( 2), b = 11.4667(2), c = 19.1413(5)Å, β = 92.0080(10)°, Z = 4, V = 2080.56(8)Å 3 ) includes molecular complex Ti 4 O(Se 2 ) 4 Br 6 based on fragment {Ti 4 (μ 4 -O)} coordinated by diselenide (Se 2 ) 2À and bromide bridging ligands. Ti 4 O(Se 2 ) 4 Br 6 is a new member of family of O-centered tetranuclear complexes with the fragment {M 4 (μ 4 -O)(Q 2 ) 4 } (M = Ti, Nb, Ta; Q=S, Se, Te); here we discuss its synthetic features, crystal and electronic structure. Experimental SectionMaterials and methods: Titanium powder (À 60 + 100 mesh, 99.5 % (metals basis)) was purchased from Alfa Aesar, selenium granules (99.997 %) and SeO 2 (99 %) was purchased from "LenPromKhim" Company (Russia), and liquid bromine (99 %) was obtained from Scientific and production association "Iodobrom" (Russia). Glass tubes from Simax Company were used for preparation of ampoules. X-ray powder diffraction (XRPD) patterns for solids were collected with a Philips PW 1830/1710 automated diffractometer (Cu Kα radiation, graphite monochromator, silicon plate as an external standard). Raman spectra were recorded with a labRAM HR Evolution spectrometer (Horiba Scientific) in the region 10-350 cm À 1 from a single crystal picked up from product Ti 4 OSe 8 Br 6 . Energy-dispersive spectroscopy (EDS) was performed with a Hitachi TM3000 device.Synthesis of the starting materials: TiSe 2 was obtained from the elements. Titanium powder (4.67 g, 97.6 mmol) and selenium granules (16.4 g, 208 mmol) in evacuated and sealed quartz ampule heated up to 750°C during 15 hours, and kept at this temperature for 15 h. Then ampule was opened and excess of selenium was removed by heating in dynamic vacuum at 350°C.

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

“…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]). Despite the general {M 4 O} compounds, or the only known layer {M 4 Q(Q 2 ) 4 } [57], no evidence of structures with a higher connectivity is known for the compounds with the {M 4 O(Q 2 ) 4 } building blocks.…”