Halides of Titanium in Lower Oxidation States
Résumé
New investigations on the di- and trihalides of titanium, TiX2 and TiX3 (X = Cl, Br, I), with their 3d2 and 3d1 electronic configurations, confirm the early observations and conclusions of Klemm. At sufficiently low temperatures, Ti─Ti single bonds are formed in the one-dimensional trihalides, i.e., Ti─Ti dimers are observed. Equally, in the two-dimensional dihalides, {Ti3} triangles occur with three single bonds. Phase transitions were detected from single-crystal or powder X-ray diffraction data, from magnetic measurements and thermal analysis. Except for the binary halides a number of ternary halides ATiX3 (extended chains of face-sharing octahedra), K4Ti3Br12 (triples of face-sharing octahedra), Na2Ti3Cl8 (triangular trimers), A3Ti2X9 (dimers of face-sharing octahedra), and A3TiX6 (isolated octahedra) as well as the mixed-valent halides CsTi2I7 (tetrahedra and octahedra) and Na5Ti3Cl12 (chains of octahedra) have been observed. Except for the triangles in titanium(II) halides, cluster compounds are rare but include K4[{OTi4}I12}] and {CTi6}Cl14.
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