A new thiostannate, (C12H25NH3)(4)[Sn2S6]. 2H(2)O, was synthesized from SnCl4, Na2S, and dodecylamine (DDA) in the ethanol-water two-solvent system at room temperature. First a suspension was obtained. With increasing crystallization time, single crystals up to several millimeters in size were found at the bottom of the vessel. The compound was characterized by single-crystal X-ray diffraction, solid state Sn-119 CPMAS NMR and C-13 CPMAS NMR, IR absorption spectroscopy, and thermal analysis. The crystal data are a = 7.533(2) Angstrom, b = 10.162(2)Angstrom, c = 21.688(4) Angstrom, alpha= 101.22(3)degrees, beta = 90.76(3)degrees, gamma 101.82(3)degrees, triclinic, space group = P (1) over bar, and Z = 1. The structure consists of one [Sn2S6](4-) anion, four n-dodecylammonium cations, and two water molecules per unit cell. The [Sn2S6](4-) dimers are formed by two edge-sharing [SnS4] tetrahedra. The hydrocarbon chains of the cations are straight with the chain direction running parallel to [001]. The chains are in van der Waals contact to each other with the nitrogen atoms pointing in opposite directions for neighboring chains. The positions of all hydrogen atoms were determined; in particular three positions were found which may suggest that the nitrogen atoms are protonated to form cationic groups. The nonorganic constituents of the-structure, i.e., anions, water molecules, and ammonium groups, interact to form an infinite layer-like unit parallel to (001).