An unprecedented in situ multiple bond cleavage of S–S, S–C(sp²) and C–N in the pyrimidinedisulfide (pym₂S₂) ligand is observed by the reaction of CuCl₂·2H₂O with this ligand under solvothermal and solvothermal-microwave conditions. In this process the formation of the compound [Cu^II(μ-Cl)(Cl)L]₂, where L represents the new ligand (L = 2-(pyrimidin-2-ylamino)-1,3-thiazole-4-carbaldehyde), is observed. This ligand has been further isolated and X-ray characterized. The similar reaction carried out under solvothermal-microwave conditions gives, in addition to the latter compound, the complex {9·[Cu(pym₂S₃)(μ-Cl)(Cl)]₂·[Cu(pym₂S₂)(μ-Cl)(Cl)]₂}. Coordination of a pyrimidinetrisulfide ligand (pym₂S₃) is reported for the first time. This work represents an illustrative example of the novel synthetic perspectives attainable via solvothermal-microwave procedures.