119Sn Solid-State NMR of Tin Sulfides. Evidence of Polytypism in SnS2

The 119Sn magic angle spinning NMR spectra of the three tin sulfides SnS, SnS2 and Sn2S3 are discussed with respect to results from x-ray structure analysis. The distortion from an octahedral environment of tin in SnS and Sn(II) in Sn2S3 is reflected in the large chemical shift anisotropy. The denser coordination sphere of Sn(IV) in SnS2 in comparison with Sn2S3 is reflected in the upfield shift observed for SnS2. With the same argument, the shift of Sn(II) in the sulfides under study is generally much lower than that of Sn(IV). The 119Sn high-resolution solid-state NMR signal of SnS2 displays a fine structure which is assigned to different polytypic regions in the crystallites.