Affiliation:
1. Institut für Anorganische Chemie , Universität Stuttgart , Pfaffenwaldring 55 , D-70569 Stuttgart , Germany , Fax: +49-711-6856-4241
2. Institut für Anorganische Chemie , Universität Stuttgart , Pfaffenwaldring 55 , D-70569 Stuttgart , Germany
Abstract
Abstract
The anion-mixed niobium tetrahalides Nb(Br0.62(4)Cl0.38(4))2Cl2 and NbI2Cl2 were obtained by heating NbBr5 with NbCl5 and NbI5 with NbCl5, respectively, in equimolar ratios with niobium metal in evacuated, torch-sealed silica ampoules at 720 K for 3 days. The orthorhombic title compounds form as very brittle black needles and were characterized by single-crystal X-ray diffraction [space group: Immm, Z=4; a=704.27(6), b=824.13(7), c=929.64(8) pm for Nb(Br0.62(4)Cl0.38(4))2Cl2 and a=753.76(6), b=829.38(7) and c=983.41(8) pm for NbI2Cl2]. Surprisingly enough, these mixed-anionic halides are not isostructural with either NbCl4, NbBr4 or NbI4, but crystallize isotypically with TaI2Cl2, thus being examples for differential site occupancy stabilized materials. Structural features of other niobium(IV) halides are compiled and compared to those of Nb(Br0.62(4)Cl0.38(4))2Cl2 and NbI2Cl2. Except for NbF4, they all exhibit chains of trans-edge connected [NbX
6]2− octahedra, which allow Peierls distortions to form Nb–Nb single bonds. The packing of these chains differ, however, depending on the actual halide or mixed-halide combination.
Reference15 articles.
1. F. P. Gortsema, R. Didchenko, Inorg. Chem.1965, 4, 182.
2. H. Schäfer, H. G. von Schnering, K. J. Niehues, H. G. Nieder-Vahrenholz, J. Less-Common Met.1965, 9, 95.
3. M. Strecker, Dissertation, University of Hannover, Hannover 1994; see also: ICDD 45–1208.
4. R. Hoppe, W. Dähne, Naturwissenschaften1962, 49, 254.
5. D. R. Taylor, J. C. Calabrese, E. M. Larsen, Inorg. Chem.1977, 16, 721.