Novel organic hybrid silver thiostannates [Hen] 4 [Ln(en) 4 ] 2 [Ag 6 Sn 6 S 20 ]·3en (Ln=Er, 1; Tm, 2; Yb, 3) were prepared by the reactions of Ln 2 O 3 , Ag, Sn and S in ethylenediamine (en) under solvothermal conditions. Six SnS 4 tetrahedra and six AgS 3 triangles are connected into the heterometallic sulfide cluster [Ag 6 Sn 6 S 20 ] 10− via edge-sharing. In the [Ag 6 Sn 6 S 20 ] 10− cluster, a hexanuclear Ag 6 S 6 core is enclosed by two Sn 3 S 10 fragments. The Ag 6 S 6 core is the first As–S cluster stabilized by inorganic SnS 4 ligands. In 1–3, all Ln 3+ ions are in 8-fold coordination environments that involved four bidentate en ligands, forming bicapped trigonal prisms. Compounds 1–3 show well-defined absorption edges with band gaps in the range of 2.18–2.47eV.