A new versatile and fast room temperature synthesis route was developed in which Na4SnS4·14H2O and selected Ni(II)amine complexes (amine = ethylenediamine (en), 1,2-diaminocyclohexane (1,2-dach), 1,2-diaminopropane (1,2-dap), 2-(aminomethyl)pyridine (2amp)) were reacted in aqueous tren (tren = tris(2-aminoethyl)amine) solutions affording crystallization of six new compounds. During the reaction heteroleptic Ni2+ centered complexes are formed in situ by replacement of two bidentate ligands by the tetradentate tren molecule. The compounds poorer in water of the pseudopolymorphs of [Ni(tren)(en)]2[Sn2S6]·xH2O (x = 2 (1) and 6 (2)) and [Ni(tren)(1,2-dach)]2[Sn2S6]·xH2O (x = 3 (3) and 4 (4)) are formed after a very short reaction time of 1 day. Remarkably, keeping the reaction slurries at room temperature for 7 days the thermodynamically stable water richer compounds were obtained. The remaining compounds, [Ni(tren)(1,2-dap)]2[Sn2S6]·4H2O (5) and [Ni(tren)(2amp)]2[Sn2S6]·10H2O (6), crystallized between 1 and 7...