The reaction of cis-[PdCl2(CNXyl)2] (Xyl = 2,6-Me2C6H3) with various 1,3-thiazol- and 1,3,4-thiadiazol-2-amines in chloroform gives a mixture of two regioisomeric binuclear diaminocarbene complexes. For 1,3-thiazol-2-amines the isomeric ratio depends on the reaction conditions and kinetically (KRs) or thermodynamically (TRs) controlled regioisomers were obtained at room temperature and on heating, respectively. In CHCl3 solutions, the isomers are subject to reversible isomerization accompanied by the cleavage of Pd-N and C-N bonds in the carbene fragment XylNCN(R)Xyl. Results of DFT calculations followed by the topological analysis of the electron density distribution within the formalism of Baders theory (AIM method) reveal that in CHCl3 solution the relative stability of the regioisomers (Delta Gexp = 1.2 kcal/mol; Delta Gcalcd = 3.2 kcal/mol) is determined by the energy difference between two types of the intramolecular chalcogen bonds, viz. S center dot center dot center dot Cl in KRs (2.8-3.0 kcal/mol) and S center dot center dot center dot N in TRs (4.6-5.3 kcal/mol). In the case of the 1,3,4-thiadiazol-2-amines, the regioisomers are formed in approximately equal amounts and, accordingly, the energy difference between these species is only 0.1 kcal/mol in terms of Delta Gexp (Delta Gcalcd = 2.1 kcal/mol). The regioisomers were characterized by elemental analyses (C, H, N), HRESI+-MS and FTIR, D-1 (H-1, C-13{1H}) and D-2 (H-1,H-1-COSY, H-1,H-1-NOESY, H-1,C-13-HSQC, H-1,C-13-HMBC) NMR spectroscopies, and structures of six complexes (three KRs and three TRs) were elucidated by single-crystal X-ray diffraction.