Reactions of N′‐(4‐oxothiazolidin‐2‐ylidene)picolinohydrazonamide (HAm4DHotaz, 1) and N′‐(3‐methyl‐4‐oxothiazolidin‐2‐ylidene)picolinohydrazonamide (Am4Motaz, 2) with K2[PdCl4] or K2[PtCl4] afforded good yields of the complexes [Pd(Am4DHotaz)Cl]·2H2O (3), [Pd(Am4DHotaz)Cl]·1/2DMF (3a), [Pt(Am4DHotaz)Cl]·3H2O (4), [Pd(Am4Motaz)Cl2]·0.5H2O (5), [Pt(Am4Motaz)Cl2]·5H2O (6), and [Pt(Am4Motaz)2]Cl2 (6a). The crystal structures of the ligands 1 and 2, and of two of the complexes, 3a and 6a, have been studied by X‐ray diffractometry. All of the new compounds were characterized by elemental analysis, mass spectrometry, IR, and 1H and 13C NMR spectroscopy and, when pertinent and allowed by the solubility of the compounds, by 195Pt NMR spectroscopy. In the square planar complexes of HAm4DHotaz, the ligand is bound to the metal atoms in an N,N,N‐terdentate deprotonated coordination mode, whereas in the dicationic complexes of Am4Motaz, the metal atom is four‐coordinated in a planar fashion by N,N atoms from two symmetry related ligands. Interesting intermolecular interactions were observed in the solid state in the ligands and complexes and these were based on hydrogen‐bonding. In particular, complex 3a formed a pseudo‐dimer, although the Pd–Pd distance between the two molecules is 3.360(1) Å, i.e. greater than the sum of van der Waal' radii.

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The reaction of 2‐cyanopyridine with N‐phenylthiosemicarbazide afforded 2‐[amino(pyridin‐2‐yl)methylidene]‐N‐phenylhydrazine‐1‐carbothioamide (Ham4ph) and crystals of 4‐phenyl‐5‐(pyridin‐2‐yl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione (pyph3NS, 1, C13H10N4S). Crystals of methyl 2‐{[4‐phenyl‐5‐(pyridin‐2‐yl)‐4H‐1,2,4‐triazol‐3‐yl]sulfanyl}acetate (phpy2NS, 2, C16H14N4O2S), derived from 1, were obtained by the reaction of Ham4ph with chloroacetic acid, followed by the acid‐catalyzed esterification of the carboxylic acid with methyl alcohol. Crystals of bis(methanol‐κO)bis(methyl 2‐{[4‐phenyl‐5‐(pyridin‐2‐yl)‐4H‐1,2,4‐triazol‐3‐yl‐κ2N1,N5]sulfanyl}acetato)zinc(II)/cadmium(II) hexabromidocadmate(II), [Zn0.76Cd0.24(C16H14N4O2S)2(CH3OH)2][Cd2Br6] or [Zn0.76Cd0.24(phpy2NS)2(MeOH)2][Cd2Br6], 3, and dichlorido(methyl 2‐{[4‐phenyl‐5‐(pyridin‐2‐yl)‐4H‐1,2,4‐triazol‐3‐yl‐κ2N1,N5]sulfanyl}acetato)mercury(II), [HgCl2(C16H14N4O2S)] or [Hg(phpy2NS)Cl2], 4, were synthesized using ligand 2 and CdBr2 or HgCl2, respectively. The molecular and supramolecular structures of the compounds were studied by X‐ray diffractometry. The asymmetric unit of 3 is formed from CdBr3 and M(phpy2NS)(MeOH) units, where the metal centre M has a 76% occupancy of ZnII and 24% of CdII. The M2+ centre of the cation, located on a crystallographic inversion centre, is hexacoordinated and appears as a slightly distorted octahedral [MN4O2]2+ cation. The Cd centre of the anion is coordinated by two terminal bromide ligands and two bridging bromide ligands that generate [Cd2Br6]2− cadmium–bromide clusters. These clusters display crystallographic inversion symmetry forming two edge‐shared tetrahedra and serve as agents that direct the structure in the formation of supramolecular assemblies. In mononuclear complex 4, the coordination geometry around the Hg2+ ion is distorted tetrahedral and comprises two chloride ligands and two N‐atom donors from the phpy2NS ligand, viz. one pyridine N atom and the other from triazole. In the crystal packing, all four compounds exhibit weak intermolecular interactions, which facilitate the formation of three‐dimensional architectures. Along with the noncovalent interactions, the structural diversity in the complexes can be attributed to the metal centre and to the coordination geometry, as well as to its ionic or neutral character.

Reaction of 2-cyanopyridine with N-phenylthiosemicarbazide afforded the 4-phenyl-5-(pyridin-2-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione. Methyl 2-((4-phenyl-5-(pyridin-2-yl)-4H-1,2,4-triazol-3-yl)thio)acetate (phpy2NS, 1), derived from this 1,2,4-triazole-3-thione, was obtained by reaction with chloroacetic acid followed by an acid-catalyzed esterification of the carboxylic acid with methyl alcohol. Synthesis of a Hg(II) complex, [Hg(phpy2NS)Cl2] (2), has been performed using the ligand (1) and HgCl2. The molecular and supramolecular structures of the ligand and the complex were studied by X-ray diffractometry.

In the present research, 5,5-dimethyl-4-phenyl-4,5-dihydro-3H-1,2,4-triazole-3-thione (1) was prepared by condensation from N-phenylhydrazinecarbothioamide, while 4-phenyl-5-(pyrazin-2-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (2) and 2-((5-(pyridin-2-yl) -4H-1,2,4-triazol-3-yl)thio)acetic acid (3) was prepared by oxidative cyclization from 2-(amino(pyrazin-2-yl)methylene)-N-phenylhydrazine-1-carbothioamide and 2-(amino(pyridine-2-yl)methylene)hydrazine-1-carbothioamide, respectively. The three compounds have been well characterized and their molecular structures studied by single-crystal X-ray diffraction. The supramolecular assembly of each crystal has also been analyzed and discussed.