A neutral Pt-II complex, dichloro(1,4,7-trithiacyclodecane-S-1,S-7-platinum, [PtCl2(C7H14S3)], and a hydrated salt of a cationic Pt-II complex, bis(1,4,7-trithiacyclodecane-S-1,S-4)platinum dichloride heptahydrate, [Pt(C7H14S3)(2)]Cl(2 .)7H(2)O, have been studied. The ten-membered heterocyclic ligand, 1,4,7-trithiacyclodecane (10S3), forms a six-membered chelate ring in the neutral complex, where the average Pt-S and Pt-Cl bond lengths are 2.255 (5) and 2.334 (4) Angstrom, respectively, and the average weak axial Pt ... S interaction distance is 3.137 (5) Angstrom. The same ligand in the cationic complex forms two five-membered chelate rings in which the average length of the four equatorial Pt-S bonds is 2.296 (2) Angstrom and the lengths of the two weak axial Pt ... S bonds are 3.159 (2) Angstrom.