Structural evolution from tin sulfide (selenide) layered structures to novel 3- and 4-connected tin oxy-sulfides

Addition of triethylenetetramine (TETN) and tetramethylammonium (TMA⁺) to SnS₂ and SnSe₂ slurries followed by heating at 150°C under autogenous hydrothermal conditions results in novel thio and thio-oxide phases. These materials crystallize in time sequence as the added amines decompose. Initially 2-D frameworks with composition (Sn₃X₇)^2-, X = S or Se are produced. In the case of the sulfides these are shown to transform to 2-D and 3-D oxy-sulfides frameworks which incorporate the decomposed template. The structures of two materials in this sequence have been determined from single crystal X-ray diffraction. The first, Sn₃Se₇ · C₆N₄H₁₆CO, designated TETN-SnSe-1, crystallizes after 1 day of digestion in space group Pbca, with a = 23.553(6), b = 14.004(6), and c = 13.967(4) Å. The structure contains SnSe₅ coordination polyhedra which form Sn₃Se⁴⁺₄ semicubes; six such semicubes are linked via Se₂ bridges to form apertures in the Sn₃Se^2-₇ sheet in (010). Similar structures occur in the TETN-SnS and TMA-SnS systems. The second material, with a framework designated SnOS-SB3, is formed after 5 days of digestion in either the TMA-SnS or TETN-SnS systems and crystallizes in C2/c, with a = 35.62(1), b = 18.468(4), c = 21.858(6) Å, and β = 115.36(1)°. The structure consists of tetrahedral clusters of composition [Sn₁₀S₂₀O₄]^8-, which are linked via single S bridges at three corners to form a 2-D framework of composition [Sn₂₀S₃₇O₈]^10-. This is one member of a theoretical structural family with composition [Sn₁₀S_20-n/2O₄]^(8-n)-, where 0 ≤ n ≤ 4 and represents the number of connections between clusters.