Tin(II) Lone Pair Stereoactivity: Influence on Structures and Properties and Mössbauer Spectroscopic Properties

The chemistry of divalent tin fluoride and chloride is rich. Stannous fluoride SnF2 itself exists under three crystallographic forms. In order to distinguish between the different phases of PbSnF4, the tetragonal phase initially prepared and characterized was named α-PbSnF4. No similar phase transitions of SrSnF4 or BaSnF4 were observed. The complexity of the X-ray powder diffraction of these phases shows a sufficiently low symmetry and large unit cell able to accommodate ordered structures and are, therefore, assumed to be ordered, although absolute proof of this will be provided only when their crystal structures are solved. The stereoactivity of the lone pair in all disordered phases was evaluated by Mössbauer spectroscopy. The stereoactivity of the lone pair, or absence of, can have serious implications on the chemical and physical properties of the materials. Some of these were described above and used to help determine their crystal structure.