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This work describes the synthesis of eight new Pd(II) and Pt(II) complexes with the general formula [M(TSC)Cl], where TSC represents the 4N-monosubstituted thiosemicarbazone derived from 2-acetylpyridine N-oxide with the substituents CH3 (H4MLO), C2H5 (H4ELO), phenyl (H4PLO) and (CH3)2 (H4DMLO). These complexes have been characterized by elemental analysis, molar conductivity, IR spectroscopy, 1H, 13C, 195Pt and ESI-MS. The complexes exhibit a square planar geometry around the metallic center coordinated by a thiosemicarbazone molecule acting as a donor ONS-type pincer ligand and by a chloride, as confirmed by the molecular structures of the complexes, [Pd(4ELO)Cl] (3) and [Pd(4PLO)Cl] (5), determined by single-crystal X-ray diffraction. The 195Pt NMR spectra of the complexes of formulae [Pt(4PLO)Cl] (6) and [Pt(4DMLO)Cl] (8) in DMSO show a single signal at −2420.4 ppm, confirming the absence of solvolysis products. Complexes 3 and 5 have been tested as catalysts in the Suzuki–Miyaura cross-coupling reactions of aryl bromides with phenylboronic acid, with yields of between 50 and 90% [ABSTRACT FROM AUTHOR]

Four lead(II) complexes featuring pyrazoylisonicotinoylhydrazone ligand paired with various anionic co-ligands (azido, thiocyanato, nitrito, and nitrato) were synthesized and thoroughly examined using structural, analytical, and spectroscopic techniques. These ligands, in their mono-deprotonated state, bind to the lead(II) ion in a tridentate manner through two nitrogen atoms and one oxygen atom. Single-crystal X-ray crystallography revealed the capacity of these molecular complexes to form larger aggregates influenced by the nature of the anion attached to the metal center. In every complex, the lead atom adopts a hemidirectional coordination environment, making it geometrically suited for tetrel bond formation. The crystal structures demonstrate that lead atoms engage in notably short interactions with nitrogen atoms, distances that are shorter than the sum of their van der Waals radii yet exceed the sum of their covalent radii. These tetrel bonds play a pivotal role in weaving the monomeric into self-assembled dimers or extended supramolecular 1D polymers. The formation and characteristics of these intriguing supramolecular structures observed in the solid state of each complex were further explored and validated through density functional theory (DFT) calculations and several computational tools like MEP, NCIPlot, QTAIM, and ELF methods. [ABSTRACT FROM AUTHOR]

Three new PbII complexes [Pb(LI)(SCN)]n, {[Pb(LII)](SCN)}n and {[Pb(HLIII)(SCN)](SCN)}n (HLI = N′-phenyl(pyridin-2-yl)methylene-N-phenylthiosemicarbazide, HLII = N′-amino(pyrazin-2-yl)methylenethiosemicarbazide, HLIII = N′-amino(pyridin-2-yl)methylenethiosemicarbazide) have been synthesized and characterized by spectroscopic techniques and single crystal X-ray diffraction. In all complexes, the corresponding organic ligand behaves as a tridentate N,N′,S-chelating species. A 1D supramolecular polymeric aggregation in complex [Pb(LI)(SCN)]n is dictated by the Pb⋯NCS and Pb⋯S＝C tetrel bonds formed between the [Pb(LI)(SCN)] species. 1D cationic coordination polymers ([Pb(LII)])nn+ in the structure of complex {[Pb(LII)](SCN)}n are linked into a 2D supramolecular polymeric layer through the Pb⋯NCS tetrel bonds and Pb⋯π(NCS) interactions formed with the nitrogen atom and the conjugated system of the free SCN− anions, respectively. The cationic species [Pb(HLIII)(SCN)]+ in the structure of complex {[Pb(HLIII)(SCN)](SCN)}n produce a 1D supramolecular polymer due to the Pb⋯SCN and Pb⋯S＝C tetrel bonds, further stabilized by the Pb⋯π(NCS) interactions formed with the conjugated system of the coordinated NCS− anion. The latter anions also link these 1D chains through the Pb⋯SCN tetrel bonds, yielding 1D supramolecular polymeric ribbons. The energetic relevance of the Pb⋯S and Pb⋯N tetrel bonds has been studied by DFT calculations. The tetrel bonds have been characterized using QTAIM and NCIplot analysis and rationalized using molecular electrostatic potential surface calculations. [ABSTRACT FROM AUTHOR]

The reaction of 2-cyanopyridine or 2-cyanopyrazine with N-methylthiosemicarbazide afforded (Z)-2-(amino(pyridin-2-yl)methylene)-N-methylhydrazinecarbothioamide (HPyAm4M) and (Z)-2-(amino(pyrazin-2-yl)methylene)-N-methylhydrazinecarbothioamide (HPzAm4M), respectively. Prolonged heating under reflux in methanol in the synthesis of these thiosemicarbazones led to the formation of 4-methyl-5-pyridin-2-yl-2,4-dihydro-[1,2,4]triazole-5-thione (HMPytat, 1) and 4-methyl-5-pyrazin-2-yl-2,4-dihydro-[1,2,4]triazole-5-thione (HMPztat, 2) by oxidative cyclization of the starting thiosemicarbazones. Reactions of thiosemicarbazones with mercury(ii) salts gave new complexes of general formulae [Hg(tat)X] (3, 4) and [Hg(Htat)2X2] (5, 7, 9–11), along with [Hg3(HEPytat)2(EPytat)2Cl4]·3H2O (6) and [Hg(EPytat)(HEPytat)I]·H2O (8) (Htat = general 1,2,4,-triazole-5-thione). The complexes were isolated as solids and were characterized by elemental analysis, mass spectrometry and IR, 1H NMR and 13C NMR spectroscopy. Recrystallization of the complexes from DMSO gave the compounds [Hg(MPytat)2]n (3a), [Hg(HMPytat)2Br2]·H2O (4a), [{Hg(HEPytat)(μ2-NS-EPytat)Cl2}2Hg] (6a), [Hg(EPytat)2]n (6b), [Hg(MPztat)2]n (10a) and [Hg(EPztat)2]n (11a) (HEPytat = 4-ethyl-5-pyridin-2-yl-2,4-dihydro-[1,2,4]triazole-5-thione and HEPztat = 4-ethyl-5-pyrazin-2-yl-2,4-dihydro-[1,2,4]triazole-5-thione). These complexes were studied by single-crystal X-ray diffraction. The structural analysis revealed the versatility of heterocyclic functionalized 1,2,4-triazole-5-thiones to coordinate to mercury(ii) in the thione and thiolate forms through the use of various donor atoms to give different and interesting crystalline packings. The supramolecular assemblies observed in the solid state were analysed. These elegant assemblies are formed by a combination of several noncovalent interactions, including intermolecular hydrogen-bonding supramolecular synthons and aromatic–aromatic interactions. The short Hg…Hg distance of 3.660 Å indicates the presence of a probable mercurophilic interaction in 6a. [ABSTRACT FROM AUTHOR]

The reactions of copper(I) iodide with N1-substituted 2-benzoylpyridine thiosemicarbazones [(C6H5)(C5H4N)C2=N3-N2H-C(=S)-N1HR (R = Me, HLMe; Et, HLEt; Ph, HLPh)] in acetonitrile/dichloromethane mixtures have formed the complexes [Cu2III2(μ4-N,N,S-LMe)2] ( 1), [CuIII(κ3-N,N,S-LEt)] ( 4), and [CuIII(κ3-N,N,S-LPh)] ( 7) through proton-coupled electron transfer (PCET), and these complexes have rare CuII-I bonds. The above thio ligands with copper(I) bromide and copper(I) chloride also formed similar CuII-Br and CuII-Cl bonds in complexes of stoichiometry [CuIIX(κ3-N,N,S-L)] (L = LMe, LEt, LPh, X = Br 2, 5, 8; X = Cl 3, 6, 9) by PCET. All of the complexes have been characterized by elemental analysis, infrared spectroscopy, electronic absorption spectroscopy, ESR spectroscopy, magnetic susceptibility measurements, molecular fluorescence, cyclic voltammetry, and single-crystal X-ray crystallography. The thio ligands coordinate as monoanionic N,N,S donors in 1- 9. The ESR data support the divalent oxidation state of the metal centers in the complexes, and the ESR parameters follow the trend g∥ > g⟂ > 2 with G values in the range 2-4, which suggests a d [ABSTRACT FROM AUTHOR]