Complexes of the types [MX2L2] and [MX2L][where M = ZnII, CdII, or HgII; X = Cl, Br, or I; L = thiomorpholin-3-one (tm) or thiazolidine-2-thione (ttz)] have been obtained as nonelectrolyte, white, diamagnetic compounds. The measurements seem to suggest for 1 : 2 derivatives a monomeric tetrahedral stereochemistry and for the 1 : 1 derivative a polymeric halide-bridged structure. The i.r. spectra suggest that the tm-derivatives are O-bonded in the case of zinc and cadmium complexes and S-bonded in the mercury ones while all ttz-derivatives are N-bonded.