Synthesis and Characterization of a Rare Transition-Metal Oxothiostannate and Investigation of Its Photocatalytic Properties.

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.