Cluster formation in Cs₂Sn₆Br₃F₁₁

The crystal structure of Cs₂Sn₆Br₃F₁₁ has been determined using single-crystal X-ray diffraction and refined by full-matrix least-squares analysis to R = 0.0736, R'= 0.0743. The complex crystallises in the monoclinic space group C2/m with a = 22.856(7), b = 4.370(3), c = 10.229(4), Å, ß = 103.94(3)° and Z = 2. All atoms lie in planes perpendicular to the b axis with an interplanar separation of b/2, which is stabilised by interactions between Sn, Br and F. There are three distinct tin sites in the structure with tin forming strong bonds to fluorine atoms only. The tin(II) sites are novel in that they contain only one short and one long Sn-F bond with the additional bonding pattern being made up from Sn-F and cluster interactions involving Br atoms. ¹¹⁹Sn Mössbauer data are presented and compared with those of other tin(II) halides.