Redetermination of tantalum penta-bromide, (TaBr(5))(2).

Crystals of di-μ-bromido-bis-[tetra-bromidotantalum(V)], (TaBr(5))(2), were obtained by recrystallization at 773 K. A first crystal structure study of (TaBr(5))(2) was reported by Rolsten [J. Am. Chem. Soc. (1958) ▶, 80, 2952-2953], who analysed the powder diffraction pattern and came to the conclusion that it crystallizes isotypically with (NbBr(5))(2) in a primitive ortho-rhom-bic cell. These findings are not in agreement with our current results of a monoclinic C-centred structure. (TaBr(5))(2) is isotypic with α-(NbCl(5))(2). The crystal structure contains [TaBr(6)] octa-hedra sharing common edges forming [TaBr(5)](2) dimers. Two crystallographically independent dimers with symmetries m and 2/m and Ta⋯Ta distances of 4.1574 (11) and 4.1551 (15) Å, respectively, are present in the structure.