Crystalline bismuth(III) dithiocarbamato-chlorido complexes [Bi{S₂CN(C₃H₇)₂}Cl₂] (I) and [Bi{S₂CN(iso-C₄H₉)₂}₂Cl] (II) were prepared and comparatively studied by (¹³C, ¹⁵N) CP-MAS NMR spectroscopy, IR spectroscopy, and X-ray diffraction (CIF files CCDC nos. 1971976 and 1971975, respectively). The dithiocarbamate ligands are typically coordinated in the S,S'-iso- (I) or aniso- (II) bidentate-terminal mode. In each of the compounds, neighboring molecules are connected through one or two μ₂-Cl– ligands into zigzag-like polymer chains, in which the central atom has sixfold coordination: [BiS₂Cl₄] (I) or [BiS₄Cl₂] (II). The binding unit in the polymer chains of I is a four-membered [Bi–(μ-Cl)₂–Bi] metallocycle in the butterfly conformation (the dihedral angle is 140.51(3)°). Therefore, stronger binding of heteroleptic molecules in polymer chains leads to a considerably shorter interatomic Bi–Bi distances in I (4.0904(4) Å) than in II (4.8772(4) Å). The thermal behavior of heteroleptic bismuth(III) complexes was studied by simultaneous thermal analysis with recording of TG and DSC curves. Although the major product of thermal transformations of I and II is Bi₂S₃, the microprobe method also identified the presence of reduced bismuth and BiCl₃.