Nickel(II)-triphenylphosphine complexes of ONS and ONN chelating 2-hydroxyacetophenone thiosemicarbazones

The complexes [Ni(L-1)(PPh3)] (1) and 1Ni(L-2)(PPh3)]-HCI (2) were synthesized by the reaction of [Ni(PPh3)Cl-2] and dibasic 2-hydroxyacetophenone-S-R-4-R-1-thiosemicarbazones (R/R-1: H/CH3, (LH2)-H-1; CH3/H, (LH2)-H-2). The ligands and the complexes were characterized using elemental analysis, IR and H-1 NMR spectra. In both complexes, the thiosemicarbazone ligands coordinate to nickel(II) by giving two protons. Complex 1 is formed through the phenolate oxygen, azomethine nitrogen and sulfur atoms of L-1 and the P acorn of a triphenylphosphine ligand. In complex 2, L-2 is functional through an ONN donor set, containing a thioamide nitrogen instead of a sulfur atom. X-ray analysis indicated distorted square planar structures for the complexes, and the nickel atoms lie slightly above the planes structured by the donor atoms. In the crystal forms of 1 and 2, some phenyl ring protons of the phosphine ligand give intramolecular hydrogen bonds with the donor atoms of the thiosemicarbazone moiety, namely the phenolate oxygen (in complexes 1 and 2) and N-4 nitrogen (in complex 2). (C) 2011 Elsevier Ltd. All rights reserved

Supramolecular nickel complex based on thiosemicarbazone. Synthesis, transfer hydrogenation and unexpected thermal behavior

The cationic thiosemicarbazone complex of nickel containing triphenylphosphine as coligand was synthesized through the isopropanol-assisted hydrogen transfer reaction. The thiosemicarbazone ligand (LH2) and its cationic nickel complex, [Ni(LH)(PPh3)]Cl-+(-)center dot(CH3)(2)CHOH, were characterized by elemental analysis, IR, H-1 NMR and UV-Vis spectroscopies. The molecular structure of the complex was also determined by single crystal X-ray diffraction technique. In addition computational studies at B3LYP/6-311G (d,p) (main group) and LANL2DZ (Ni) level were carried out for theoretical characterization of the ligand and complex. Structural analysis of the complex indicated the presence of square-planar coordination geometry (ONNP) about nickel in which the thiosemicarbazone ligand coordinated as mononegative tridentate. Isopropyl alcohol catalyzed efficiently the transfer hydrogenation and the cationic complex formed through inter conversion azinyl-azinylidene. All spectral data support the formation of the ligand and its nickel complex and the results calculated using theoretical methods coincide well with the experimental findings. The thermal degradation of the complex was investigated using thermogravimetric and differential thermal analyses techniques in nitrogen and oxygen atmosphere. The oxidative-thermal decomposition of the compound showed volatilization of nickel as unexpected behavior unlike nitrogen atmosphere. (C) 2016 Elsevier Ltd. All rights reserved

Divalent nickel complexes of thiosemicarbazone based on 5-bromosalicylaldehyde and triphenylphosphine: Experimental and theoretical characterization

Two nickel(II) complexes containing 5-bromosalicylidene-N-methyl-S-methyl-isothiosemicarbazone (H(2)SMeNMeTsc) and 5-bromosalicylidene-N-methyl-thiosemicarbazone (H(2)NMeTsc) with triphenylphosphine were synthesized. The compounds were characterized by elemental analysis, IR, H-1 NMR and UV-Vis spectroscopies, and their structures were determined by single crystal X-ray diffraction technique. Theoretical characterization of the compounds was carried out using the density functional theory (DFF/B3LYP) method with 6-311G(d,p) basis set for the C, H, Br, N, O, P, S atoms and LANL2DZ pseudo-potential for Ni atom, and the results were checked against the experimental data. Electronic absorption spectra of the compounds have also been obtained using the time-dependent density functional theory (TD-DFT) formalism at the same level. The coordination geometry around Ni-II in the two complexes is distorted square-planar geometry. While the thiosemicarbazone ligand is coordinated to nickel through ONN mode in [Ni(SMeNMeTsc)(PPh3)]center dot PPh3, it is bound to the metal as dianionic ONS donors in [Ni(NMeTsc)(PPh3)]. The consistency between theoretical and experimental values is good in general. (C) 2016 Elsevier Ltd. All rights reserved

Nickel(II)-PPh3 Complexes of S,N-Substituted Thiosemicarbazones - Structure, DFT Study, and Catalytic Efficiency

Five 2-hydroxyacetophenone thiosemicarbazones with [-(NH)-H-4-R-(SH)J (where R is ethyl or phenyl) and [-(NH)-H-4-R- (SR1)] (where R/R-1 denote methyl/methyl, methyl/propyl, or phenyl/methyl) substituents on the thioamide group were synthesized. The ligands have an ONS or ONN donor set, and the reaction of the dibasic ligands with [Ni(PPh3)(2)Cl-2] yields chelate complexes with general formula [Ni(L)(PPh3)]. The stable solid complexes were characterized by IR and H-1 NMR spectroscopy and elemental analysis. The crystallographic structures of two complexes, one with an S-methyl-N-4-phenyl- and the other with an S-propyl-N-4-methyl-substituted thiosemicarbazidato ligand, are reported. The complexes crystallize in the monoclinic space group P2(1)/n, and the nickel centers have a distorted square planar environment. The coupling reaction of phenylmagnesium bromide with bromobenzene was used to determine the catalytic activities of the nickel(11) complexes prepared, and the results show that the ONN complexes provide higher yields relative to those with ONS donors. The catalytic efficiency of the nickel complexes was modeled by using density functional theory (DFT)

Electrochemistry and structural properties of new mixed ligand nickel(II) complexes based on thiosemicarbazone

Mixed ligand nickel(II) complexes of 5-chloro-2-hydroxybenzophenone-N-R-thiosemicarbazone (R: -CH3 (L-1), -CH2-CH=CH2 (L-II)) and triphenylphosphine were synthesized. The structures of the complexes were characterized by elemental analysis, IR, H-1 and P-31 NMR spectroscopy, conductivity, electrochemical and magnetic moment measurements, and single-crystal X-ray diffraction technique. The two nickel(II) complexes have a square planar geometry containing O, N, and S atoms of the thiosemicarbazone, and the P atom of triphenylphosphine. The electrochemical behaviors of the thiosemicarbazone ligands and the nickel complexes were studied using cyclic voltammetry and square wave voltammetry. The redox processes of the compounds were significantly influenced by the central metal ions and the nature of the substituents on the thiosemicarbazones, which are the important factors in controlling the redox properties. In situ spectroelectrochemical studies were employed to determine the colors and spectra of the electro-generated species of the complexes

5-Methyl-2-hydroxy-acetophenone-thiosemicarbazone and its nickel(II) complex: Crystallographic, spectroscopic (IR, NMR and UV) and DFT studies

http://www.sciencedirect.com/science/article/pii/S027753871500771

Spectroscopic, electrochemical and X-ray diffraction studies on nickel(II)-complexes of acetophenone thiosemicarbazones substituted six-carbon groups

Reactions of [Ni(PPh3)(2)Cl-2] with 3-Bromo-5-chloro-2-hydroxyacetophenone-N-4-hexyl ((LH2)-H-1), cyclohexyl (L2H2) and phenyl ((LH2)-H-3)-thiosemicarbazones resulted in four coordinated (ONSP) nickel(II) complexes, [Ni(L-1)(PPh3)] (1), [Ni((LH)-H-2)(PPh3)]center dot Cl (2) and [Ni(L-3)(PPh3)]center dot C2H5OH (3). The structures of 1-3 were determined by spectroscopic and single crystal X-ray diffraction methods. While formation of complexes 1 and 3 occurs through the doubly deprotonated forms of the thiosemicarbazone ligands (L-1 and L-3), complex 2 consists of mono deprotonated ligand ((LH)-H-2). Cyclic voltammetry and square wave voltammetry studies of the compounds showed that all ligands represented one irreversible reduction and two irreversible oxidation processes. Complexes 1-3 illustrated a metal based reduction and a metal based oxidation processes in addition to the ligand based electron transfer reactions. In situ spectroelectrochemical measurements were employed to determine the spectra of electrogenerated species of the complexes and to assign the redox processes. The influences of the N-4-substituent types on structural and electrochemical features of the compounds were discussed. (C) 2015 Elsevier B.V. All rights reserved

Quantum-chemical, spectroscopic and X-ray diffraction studies on nickel complex of 2-hydroxyacetophenone thiosemicarbazone with triphenylphospine

Reaction of 2-hydroxyacetophenone thiosemicarbazone with [Ni(PPh(3))(2)Cl(2)] in optimized conditions afforded a mixed ligand complex with an isolated triphenylphosphine molecule. The structure was characterized by elemental analysis, IR, NMR and UV-Vis. spectroscopies and single crystal X-ray diffraction technique. In addition, the molecular geometry, vibrational frequencies and gauge including atomic orbital (CIAO) (1)H and (13)C NMR chemical shift values of the title compound in the ground state have been calculated using the density functional theory (DFT/B3LYP) method with the 6-31G(d,p) basis set for the C. N, O, S, P. H atoms and LANL2DZ pseudo-potential for the Ni atom, and compared with the experimental data. Besides, atomic charge distributions, molecular electrostatic potential and frontier molecular orbitals (FMO) analysis of the title compound were investigated by theoretical calculations. The thermodynamic properties of the compound at different temperatures have been calculated and corresponding relations between the properties and temperature have also been obtained. Atomic charge distributions indicate that during forming the title compound, the free ligand of thiosemicarbazone ion transfers their negative charges to central Ni(II) ion. The effect of different solvents (chloroform, methanol and water) on the geometry, vibrational frequencies, total energies and dipole moments was studied using the density functional theory (DFT/B3LYP) method by applying the Onsager and the Polarizable Continuum Model (PCM). (C) 2010 Elsevier Ltd. All rights reserved