The new transition-metal oxothiostannate [Ni­(cyclen)­(H2O)2]4[Sn10S20O4]·∼13H2O (1) was prepared under hydrothermal conditions using Na4SnS4·14H2O as the precursor in the presence of [Ni­(cyclen)­(H2O)2]­(ClO4)2·H2O. Compound 1 comprises the [Sn10S20O4]8– anion constructed by the T3-type supertetrahedron [Sn10S20] and the [Sn10O4] anti-T2 cluster. Channels host the H2O molecules, and the sample can be reversibly dehydrated and rehydrated without significantly affecting the crystallinity of the material. 119Sn NMR spectroscopy of an aqueous solution of Na4SnS4·14H2O evidences that between 25 and 120 °C only [SnS4]4– and [Sn2S6]4– anions are present. In further experiments, hints were found that the formation of tin oxosulfide ions depends on the Ni2+-centered complexes. Compound 1 exhibits promising photocatalytic properties for the visible-light-driven hydrogen evolution reaction, with 18.7 mmol·g–1 H2 being evolved after 3 h.

The new compounds [Ni(L1)][Ni(L1)Sn2S6]n·2H2O (I) and [Ni(L2)]2[Sn2S6]·4H2O (II) containing the macrocyclic ligands L1 (L1 = 1,8‐dimethyl‐1,3,6,8,10,13‐hexaazacyclotetradecane) and L2 (L2 = 1,8‐diethyl‐1,3,6,8,10,13‐hexaazacyclotetradecane) were prepared at room temperature by overlaying an aqueous solution of Na4SnS4·14H2O with the [Ni(L1)](ClO4)2 complex dissolved in CH3CN (I) or by overlaying a solution of the [Ni(L2)](ClO4)2 complex dissolved in DMSO with an aqueous solution of Na4SnS4·14H2O (II). The slow interdiffusion of the two solvents guarantees supersaturation in the interface region of the solvents so that crystallization of the compounds occurs. In the structure of I one Ni2+ cation has bonds to S2– anions of the thiostannate anion thus generating chains along [100]. This cation is in an octahedral environment of four N atoms of L1 and two S atoms of the [Sn2S6]4– anion. The second [Ni(L1)]2+ complex exhibits a square‐planar coordination geometry. These [Ni(L1)]2+ complexes and water molecules are located between the chains. In the structure of II isolated [Sn2S6]4– anions and [Ni(L2)]2+ cations are observed. The Ni2+ cations are fourfold coordinated by N atoms of the L2 ligand and feature also a square planar environment.

We present the convenient synthesis and characterization of the new ternary thiostannate Na 4 SnS 4 (space group I4 1 =acd) by directed removal of crystal water molecules from Na 4 SnS 4 •14 H 2 O. The compound represents a new kinetically stable polymorph of Na 4 SnS 4 , which is transformed into the known, thermodynamically stable form (space group P � 42 1 c) at elevated temperatures. Thermal co-decomposition of mixtures with Na 3 SbS 4 •9 H 2 O generates solid solution products Na 4À x Sn 1À x Sb x S 4 (x = 0.01, 0.10) isostructural to the new polymorph (x = 0). Incorporation of Sb 5 + affects the bonding and local structural situation noticeably evidenced by X-ray diffraction, 119 Sn and 23 Na NMR, and 119 Sn Mössbauer spectroscopy. Electrochemical impedance spectroscopy demonstrates an enormous improvement of the ionic conductivity with increasing Sb content for the solid solution (σ 25°C = 2 × 10 À 3 , 2 × 10 À 2 , and 0.1 mS cm À 1 for x = 0, 0.01, and 0.10), being several orders of magnitude higher than for the known Na 4 SnS 4 polymorph.

The new transition metal oxo‐thiostannate {[Ni(cyclen)]6[Sn6S12O2(OH)6]}·2(ClO4)·19H2O (1) was prepared under hydrothermal conditions using Na4SnS4·14H2O and [Ni(cyclen)](ClO4)2 as reactants. In the crystal structure the rare [Sn6S12O2(OH)6]10– anion is observed, which is composed of SnS2O(OH)3 and SnS4O2 octahedra, and SnS4 tetrahedra sharing edges and corners. The anion is expanded by six Ni2+ centered complexes via Ni–S and Ni–OH bonds. The photocatalytic properties for the visible light driven hydrogen evolution reaction shows that 26.6 mmol·g–1 H2 were evolved after 3 h.

A highly unusual solid-state epitaxy-induced phase transformation of Na 4 SnS 4 • 14H 2 O (I) into Na 4 Sn 2 S 6 • 5H 2 O (II) occurs at room temperature. Ab initio molecular dynamics (AIMD) simulations indicate an internal acid-base reaction to form [SnS 3 SH] 3À which condensates to [Sn 2 S 6 ] 4À . The reaction involves a complex sequence of OÀ H bond cleavage, S 2À protonation, SnÀ S bond formation and diffusion of various species while preserving the crystal morphology. In situ Raman and IR spectroscopy evidence the formation of [Sn 2 S 6 ] 4À . DFT calculations allowed assignment of all bands appearing during the transformation. X-ray diffraction and in situ 1 H NMR demonstrate a transformation within several days and yield a reaction turnover of � 0.38 %/h. AIMD and experimental ionic conductivity data closely follow a Vogel-Fulcher-Tammann type T dependence with D(Na) = 6 × 10 À 14 m 2 s À 1 at T = 300 K with values increasing by three orders of magnitude from À 20 to + 25 °C.