Reactions of [Cu(PPh 3 ) 3 Cl] with heterocyclic thiones (L) (L = pyridine-2-thione (py2SH), 1,3-thiazolidine-2-thione (tzdtH), benz-1,3-imidazoline-2-thione (bzimtH 2 ), benz-1,3-thiazoline-2-thione (bztztH), 4,5-diphenyl-imidazol-2-thione (dpimtH), 3-methylbenz-1,3-thiazoline-2-thione (mbztztH), 6-ethoxybenz-1,3-thiazoline-2-thione (etbztztH), 4-hydroxy-5-methyl-pyrimidine-2-thione (hympmtH), 4,6-dimethyl-pyrimidine-2-thione (dmpmtH), 4-mercapto-1H-pyrazolo[3,4d] pyrimidine (pyrpmtH) and quinoline-2-thione (quintH) yield mononuclear complexes of the general formula [Cu(PPh 3 ) 2 (L)Cl]. The complexes were characterized by various physicochemical methods. The crystal structure of [Cu(PPh 3 ) 2 (tzdtH)Cl] was determined by single-crystal X-ray diffraction methods. The yellow crystals are monoclinic, space group P2 1 /c with a = 14.31(2), b = 10.099(10), c = 24.52(2) 9, β = 93.53(7)° and Z = 4. The copper atom has a pseudo-tetrahedral geometry with bond lengths Cu-S = 2.418(5), Cu-Cl = 2.344(3), Cu-P(1) = 2.287(3) and Cu-P(2) = 2.298(2) 9. The structure was solved by direct methods with a final R value of 0.0562.