Structural influences of fluorine ligand in niobium cluster chemistry: crystal structures of KNb6Cl10F5 and CsNb6Cl8F7

We have synthesized by solid state chemistry and structurally characterized by single crystal X-ray diffraction two new cluster compounds, KNb6Cl10F5 and CsNb6Cl8F7. KNb6Cl10F5 is a Ta6Cl15 derived structure, whereas CsNb6Cl8F7 exhibits a primitive framework derived from Nb6F15. In both structures, fluorine and chlorine are randomly distributed on the ligand positions, but in CsNb6Cl8F7 fluorine fully occupies the apical positions. The comparison between the geometrical parameters of the title compounds and those observed in previously isolated Nb6 chlorofluorides, halides and fluorides, allows specification of the influence of fluorine in niobium cluster chemistry.