Thiosemicarbazone Complexes of Transition Metals as Catalysts for Cross-Coupling Reactions

Palladium(II) and Platinum(II) Complexes Bearing ONS-Type Pincer Ligands: Synthesis, Characterization and Catalytic Investigations

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.

Transition Metal Complexes of Thiosemicarbazides, Thiocarbohydrazides, and Their Corresponding Carbazones with Cu(I), Cu(II), Co(II), Ni(II), Pd(II), and Ag(I)-A Review

This review focuses on some interesting and recent applications of transition metals towards the complexation of thiosemicarbazides, thiocarbohydrazides, and their corresponding carbazones. We started the review with a description of the chosen five metals, including Cu[Cu(I), Cu(II], Co(II), Ni(II), Pd(II), and Ag(I) and their electronic configurations. The stability of the assigned complexes was also discussed. We shed light on different routes describing the synthesis of these ligands. We also reported on different examples of the synthesis of Cu(I), Cu(II), Co(II), Ni(II), Ag(I), and Pd(II) of thiosemicarbazide and thiocarbohydrazide complexes (until 2022). This review also deals with a summary of the fruitful use of metal complexes of thiosemicarbazones and thiocarbazones ligands in the field of catalysis. Finally, this recent review focuses on the applications of these complexes related to their biological importance.

Synthesis and structures of dinuclear palladium complexes with 1,3-benzimidazolidine-2-thione and 1,3-imidazoline-2-thione

The synthesis and structures of dinuclear palladium complexes with 1,3-benz-imidazolidine-2-thione (bzimtH) and 1,3-imidazoline-2-thione (imtH) are reported, namely, bis-(μ-1H-benzimidazole-2-thiol-ato)-κ2 N 3:S;κ2 S:N 3-bis-[cyanido(tri-phenyl-phosphine-κP)palladium(II)], [Pd2(C7H5N2S)2(CN)2(C18H15P)2] or [Pd2(μ-N,S-bzimtH)2(CN)2(PPh3)2] (1), and bis-(μ-1H-imidazole-2-thiol-ato)-κ2 N 3:S;κ2 S:N 3-bis-[cyanido(tri-phenyl-phosphine-κP)palladium(II)] aceto-nitrile 0.58-solvate, [Pd2(C3H3N2S)2(CN)2(C18H15P)2]·0.58C2H3N or [Pd2(μ-N,S-imtH)2(CN)2(PPh3)2]·0.58C2H3N (2). The compound [Pd2(μ-N,S-bzimtH)2(CN)2(PPh3)2] is located on a crystallographic twofold axis while [Pd2(μ-N,S-imtH)2(CN)2(PPh3)2]. 0.58(C2H3N) contains two partially occupied aceto-nitrile solvent mol-ecules with occupancies of 0.25 and 0.33. In both of these compounds, the anionic bzimtH- and imtH- ligands coordinate through N,S-donor atoms in a bridging mode, covering four coordination sites of two metal centers and other two sites are occupied by two PPh3 ligand mol-ecules. Finally, the remaining two sites of two metal centers are occupied by cyano groups, abstracted by the metals from the solvent during reaction. In the packing of the 1,3-benzimidazolidine- 2-thione and 1,3-imidazoline-2-thione complexes, there are intra-molecular π-π inter-actions involving the thione moiety as well as an N-H⋯N hydrogen bond linking the thione and cyano ligands. In addition, in 2, as well as the π-π inter-action involving the thione moieties, there is an additional π-π inter-action involving one of the thione moieties and an adjacent phenyl ring from the tri-phenyl-phosphine ligand. There are also C-H⋯N inter-actions between the imidazoline rings and the aceto-nitrile N atoms.

Influence of the Reaction Conditions in the Crystal Structures of Zn(II) and Ni(II) Coordination Compounds with a Dissymmetric Bis(Thiosemicarbazone) Ligand

The new ligand HMeATSM, derived from condensation of 2-3-butanedione with 4-methyl-3-thiosemicarbazide and 2,4-dimethyl-3-thiosemicarbazide, has been synthesized. Its reactivity with nickel(II) and zinc(II) nitrates was explored and the resulting complexes were thoroughly characterized by elemental analysis, conductivity, mass spectrometry, IR, 1H and 13C NMR spectroscopies and their structures were confirmed by single-crystal X-ray diffraction. The results showed that the complex [Ni(MeATSM)]NO3 1 is formed under every reaction condition. In contrast, the reaction with zinc(II) nitrate depends on the temperature and the presence of LiOH.H2O, leading to the obtaining of complexes [Zn(MeATSM)(OH2)](NO3) 2 and [Zn(Me2TS)2(OH2)](NO3)2 3. The crystal structures of complexes 1 and 2 show that the dissymmetric ligand acts as a N2S2 tetradentate monoanionic ligand. The structural preferences of the metals also determine the structure of the complexes: whereas nickel(II) is in a square-planar environment, the zinc atom prefers a distorted square-base pyramid geometry imposed by the coordination mode and the planarity of the bis(thiosemicarbazone) ligand. In contrast, in complex 3, containing two bidentate Me2TS ligands, the Zn(II) is in a trigonal bipyramid arrangement. In all the complexes, the nitrate ion is not coordinated to the metal and acts as a counterion.

Reactions of copper(II) bromide with 2,6-diacetylpyridine bis(phenyl-hydrazone) (L)-molecular and crystal structure of L and its mixed-valence complex [CuIIL2][CuI2Br4]

Utilizing X-ray crystallography, the crystal and molecular structures of 2,6-diacetylpyridine bis(phenylhydrazone) (L) were determined. The energetics of the intermolecular interactions in the crystal structure were assessed with computational methods, revealing that dispersion interactions are dominant. The basic structural unit of the crystal packing was revealed to be the herring-bone type arrangement of L molecules. Assignation of the IR spectrum of L with the aid of DFT calculations was performed. Furthermore, new reactions of L with CuBr2 in different solvents are described, which led to the synthesis of the mixed Cu(II)?Cu(I) complex with the formula [CuIIL2][CuI2Br4] (1), and its structural characterization. In the complex cation, two molecules of tridentate N3 ligand are meridionally arranged in a very distorted octahedral environment of a Cu(II) ion. In [Cu2Br4]2-, the bromide ions are arranged in a trigonal-planar geometry around each copper(I) atom. Finally, for ligand, 1, and the previously synthesized complex [CuL2]Br2, the thermal properties were examined. The thermal stability of the complexes were lower than that of the ligand and decrease in the order: L (250?C) > [CuL2]Br2 (221?C) > [CuIIL2][CuI2Br4] (212?C). The differences in thermal stability of the complexes are due to differences in the packing efficacy of the constitutional ions.

Editorial Catalysts: Special Issue on Transition Metal Catalyzed Cross-Coupling Reactions

Transition metal catalyzed cross-coupling reactions have proved to be powerful tools for carbon–carbon as well as carbon–heteroatom bond formation in the development of synthetic methodologies for applications ranging from pharmaceuticals to materials [...]

Organosulfur, organoselenium, and organotellurium ligands in the development of palladium, nickel, and copper-based catalytic systems for Heck coupling

Organosulfur, organoselenium, and organotellurium ligands in designing Pd, Ni, and Cu-based homogeneous, heterogeneous, and nanocatalytic systems for Heck coupling.