Structural and magnetic studies of Schiff base complexes of nickel(ii) nitrite: change in crystalline state, ligand rearrangement and a very rare μ-nitrito-1κO:2κN:3κO′ bridging mode

Four new nickel(II) complexes, [Ni2L2(NO2)2]·CH2Cl2·C2H5OH, 2H2O (1), [Ni2L2(DMF)2(m-NO2)]ClO4·DMF (2a), [Ni2L2(DMF)2(m-NO2)]ClO4 (2b) and [Ni3L¢2(m3-NO2)2(CH2Cl2)]n·1.5H2O (3) where HL = 2-[(3-amino-propylimino)-methyl]-phenol, H2L¢ = 2-({3-[(2-hydroxy-benzylidene)-amino]-propylimino}-methyl)-phenol and DMF = N,N-dimethylformamide, have been synthesized starting with the precursor complex [NiL2]·2H2O, nickel(II) perchlorate and sodium nitrite and characterized structurally and magnetically. The structural analyses reveal that in all the complexes, NiII ions possess a distorted octahedral geometry. Complex 1 is a dinuclear di-m2-phenoxo bridged species in which nitrite ion acts as chelating co-ligand. Complexes 2a and 2b also consist of dinuclear entities, but in these two compounds a cis-(m-nitrito-1kO:2kN) bridge is present in addition to the di-m2-phenoxo bridge. The molecular structures of 2a and 2b are equivalent; they differ only in that 2a contains an additional solvated DMF molecule. Complex 3 is formed by ligand rearrangement and is a one-dimensional polymer in which double phenoxo as well as m-nitrito-1kO:2kN bridged trinuclear units are linked through a very rare m3-nitrito-1kO:2kN:3kO¢ bridge. Analysis of variable-temperature magnetic susceptibility data indicates that there is a global weak antiferromagnetic interaction between the nickel(II) ions in four complexes, with exchange parameters J of -5.26, -11.45, -10.66 and -5.99 cm-1 for 1, 2a, 2b and 3, respectively

Thermoanalytical study of the complexes of 4-dimetilaminocinnamylidenepiruvate with manganese (II), cobalt (II), nickel (II), cupper (II), zinc (II) and lead (II), in the solid state

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Oxidation of nickel(II) cyclam and tetraglycine complexes by dissolved oxygen in the presence of sulfur(IV). Synergistic effects of manganese(III) and cobalt(III)

The autoxidation of [Ni-II(cyclam)](2+) (cyclam = 1,4,8,11-tetraazacyclotetradecane) and Ni(II)tetraglycine, accelerated by S-IV is studied spectrophotometrically by following the formation of Ni-III complexes.

Thermoanalytical study of the complexes of 4-dimethylaminocynnamylidenepyruvate with manganese (II), cobalt (II), nickel (II), cupper (II), zinc (II) and lead (II), in the solid state

Solid state compounds M-4-DMCP, where 4-DMCP is 4-dimethylaminocynnamylidenepyruvate and M represents Mn (II), Co (II), Ni (II), Cu (II), Zn (II) and Pb (II) were prepared. These compounds were studied by thermoanalytical techniques: thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), X-ray diffraction powder patterns and complexometric titration with EDTA. From the results obtained by the complexometric titration with EDTA, TG, DTG and DSC curves, was possible to establish the hydration degree, stoichiometry and thermal stability of the prepared compounds.

Cobalt(II) and nickel(II) complexes with djenkolic acid

Cobalt(II) and nickel(II) djenkolates CoC7H12N2O4S2. H2O (I) and NiC7H12N2O4S2. H2O (II) were synthesized by the reaction of potassium djenkolate with the respective chlorides. LR spectra suggested coordination via the COO- and NH2 groups for the ligands in both compounds. Visible absorption spectra confirmed the octahedral structure of the complexes. X-ray powder diffraction patterns were indexed in the orthorhombic and monoclinic unit cells with parameters: a = 11.35, b = 7.35, c = 6.85 Angstrom for I and a = 11.54, b = 7.45, c = 6.90 Angstrom, beta = 94.95 degrees for II.

Combination of nickel and titanium complexes containing nitrogen ligands as catalyst for polyethylene reactor blending

Ethylene was polymerized using a combination of Ni(diimine)Cl-2 (1) (diimine = 1,4-bis(2,6-di-isopropylphenyl)-acenaphthenediimine) and {Tp(Ms)*} TiCl3 (2) (Tp(Ms)* = hydridobis(3-mesitylpyrazol-1-yl)(5-mesityl-pyrazol-1-yl)) compounds in the presence of methyl-aluminoxane (MAO) at 30 degrees C. The productivity reaches a maximum at X-Ni = 0.75 (1400 kg of PE/mol[M] . h), and the produced polyethylene (PE) showed maximal melt flow index (0.13 g/10 min) and minimal intrinsic viscosity (2.24 dL/g) compared to polyethylenes obtained with different values of nickel loading fractions (X-Ni). Productivity intrinsic viscosity data, as well as melt flow index measurements markedly depend upon the content of the late transition metal, thus suggesting a synergic effect between nickel and titanium catalysts.

Thermal studies on nickel(II) 4-iodopyrazole complexes

This work describes the synthesis, IR and UV-Vis spectroscopic characterization as well the thermal behavior of the [NiCl2(HIPz)(4)]center dot C3H6O (1), [Ni(H2O)(2)(HIPz)(4)](NO3)(2) (2), [Ni(NCS)(2)(HIPz)(4)] (3) and [Ni(N-3)(2)(HIPz)(4)] (4) (HIPz = 4-iodopyrazole) pyrazolyl complexes. TG experiments reveal that the compounds 1-4 undergo thermal decomposition in three or four mass loss steps yielding NiO as final residue, which was identified by X-ray powder diffraction.

Syntheses and luminescent properties of tetrahedral nickel(0) complexes

Tetrahedral nickel(0) complexes [NiL4], [Ni(dppe)2] and [Ni(CO)2(SbPh3)2] (L=AsPh3, SbPh3, P(OPh)3, dppe=1,2-bis(diphenylphosphino)ethane) were prepared by reduction of NiCl2·6H2O with NaBH4 under N2 or CO atmosphere in the presence of the ligand. The complex [Ni(SbPh3)4] was also obtained by electrolysis at -1.3 V (Ag/Ag+), under a platinum gauze, of the system NiCl2·6H2O/SbPh3 (molar ratio=1:4). These complexes, both in the solid state and in solution, show an orange emission at room temperature, when excited with UV radiation. A qualitative molecular orbital diagram for the [NiL4] complexes is proposed. Electronic absorption spectra of the complexes show bands near 400 nm assigned as MLCT π*2e←d2t2. A 1A1←3T1 transition is suggested for the emission observed in these systems. Lifetimes in microsecond range were estimated from time-resolved emission spectra. Spectroscopic properties of the free ligands have also been investigated.

Thermal study of nickel(II) pyrazolyl complexes

The thermal behavior of the pyrazolyl complexes [NiCl2(HPz) 4] (1), [Ni(NCS)2(HPz)4] (2), [NiCl 2(HdmPz)4]·2H2O (3) and [Ni(NCS) 2(HdmPz)4]·2H2O (4) (HPz=pyrazole, HdmPz=3,5-dimethylpyrazole) has been studied by thermogravimetry (TG) and differential thermal analysis (DTA). The TG data indicated that the thermal stability of [NiX2(HL)4] (X=Cl, NCS) compounds varies depending on the pyrazolyl ligand in the following order HL=HPz>HdmPz. From the thermal decomposition of 3 and 4 it was possible to isolate the intermediate compounds [Ni(μ-Cl)2(HdmPz)2] (3a) and [Ni(μ-1,3-NCS) 2(HdmPz)2] (4a), respectively. The final products of the thermal decompositions of 1-4 were identified as NiO by X-ray powder diffraction. © 2005 Akadémiai Kiadó, Budapest.

Electropolymerization using binuclear nickel(II) Schiff base complexes bearing N4O4 donors as supramolecular building blocks

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermal analysis of coordination compounds. Part 1. Thermodecomposition of nickel(II) triphenylphosphine complexes with halides, nitrate, and thiocyanate

The compounds [NiX 2(PPh 3) 2] (where X is Cl -, Br -, I -, NO - 3, NCS -; and PPh 3 is triphenylphosphine) were prepared and characterized by infrared and atomic absorption spectroscopies and by carbon and hydrogen analyses. Simultaneous thermogravimetric (TG) and derivative thermogravimetric (DTG) curves of these complexes were recorded in air. The decrease in mass observed indicates conversion of the complexes to oxides. The thermal decomposition of the halogen and nitrate complexes occurred in a number of steps; the thiocyanate complex decomposed in a single step. © 1994.

Correlation between i.r. spectra and thermal decomposition of cobalt(II), nickel(II), copper(II) and mercury(II) complexes with piperidinedithiocarbamate and pyrrolidinedithiocarbamate

The thermal decomposition of pyrrolidinedithiocarbamate and piperidinedithiocarbamate complexes of CoII, NiII, CuII and HgII have been studied by thermogravimetry and differential scanning calorimetry. The decomposition intermediates and final products were identified by their X-ray diffraction patterns. The i.r. spectra are discussed in terms of the thermal decomposition pathways.

Synthesis, characterization and X-ray crystal structures of dinuclear nickel(II) complexes of a novel potentially hexadentate but functionally tetradentate binucleating ligand

A binucleating potentially hexadentate chelating agent containing oxygen, nitrogen and sulfur as potential donor atoms (H2ONNO) has been synthesized by condensing alpha,alpha-xylenebis(N-methyldithiocarbazate) with 2,4-pentanedione. An X-ray crystallographic structure determination shows that the Schiff base remains in its ketoimine tautomeric form with the protons attached to the imine nitrogen atoms. The reaction of the Schiff base with nickel(II) acetate in a 1:1 stoichiometry leads to the formation of a dinuclear nickel(II) complex [Ni(ONNO)](2) (ONNO2- = dianionic form of the Schiff base) containing N,O-chelated tetradentate ligands, the sulfur donors remaining uncoordinated. A single crystal X-ray structure determination of this dimer reveals that each ligand binds two low spin nickel(II) ions, bridged by a xylyl group. The nickel(II) atoms adopt a distorted square-planar geometry in a trans-N2O2 donor environment. Reaction of the Schiff base with nickel(II) acetate in the presence of excess pyridine leads to the formation of a similar dinuclear complex, [Ni(ONNO)(py)](2), but in this case comprises five coordinate high-spin Ni(II) ions with pyridine ligands occupying the axial coordination sites as revealed by X-ray crystallographic analysis. (c) 2005 Published by Elsevier B.V.

Nickel(II) complexes of whole set of the simple ethylenediaminetetracarboxylate ligands:DFT study of complexes invoking molecular orbital and configurational analysis

The whole set of the nickel(II) complexes with no derivatized edta-type hexadentate ligands has been investigated from their structural and electronic properties. Two more complexes have been prepared in order to complete the whole set: trans(O5)-[Ni(ED3AP)]2- and trans(O5O6)-[Ni(EDA3P)]2- complexes. trans(O5) geometry has been verified crystallographically and trans(O5O6) geometry of the second complex has been predicted by the DFT theory and spectral analysis. Mutual dependance has been established between: the number of the five-membered carboxylate rings, octahedral/tetrahedral deviation of metal-ligand/nitrogen-neighbour-atom angles and charge-transfer energies (CTE) calculated by the Morokuma’s energetic decomposition analysis; energy of the absorption bands and HOMO–LUMO gap.