Coordination mode and reactivity of nickel(II) with vitamin B6

This contribution presents a selection of results obtained using spectrophotometric and potentiometric titrations. For several reasons, the investigated equilibria present particular challenges to traditional analysis techniques. Equilibrium constants and UV–vis absorption spectra for different ligands in the complexation process of Ni(II) with pyridoxamine (pm), pyridoxal (pl) and pyridoxine are reported. The gradual and cumulative stability constants occurring in aqueous solution are presented for all complexes studied. Additionally, crystal-field parameters were calculated for two nickel(II) complexes synthesized, [Ni(pm)₂]Cl₂ and [Ni(pl)₂]Cl₂, respectively. The minimum inhibitory concentration and minimal bactericidal/fungicidal concentration values for Ni(II) complexes studied were obtained at 25 °C for 24–48 h. The activity data show that the complexes are more potent antimicrobials than the parent ligands.     

1,1,1-Tris(diphenylphosphinemethyl)ethane complexes of nickel and platinum with tin

Summary This paper describes a series of bimetallic compounds derived from the starting complexes [Ni(tdpme)Cl₂] and [Pt(tdpme)Cl₂] [where tdpme = 1,1,1-tris(diphenylphosphinemethyl) ethane, MeC(CH₂PPh₂)₃] upon reaction with Ph₃SnCl and NaBH₄, as well as with SnCl₂. In the first case, a direct bond between tin and the transition metal is formed (with concomitant reduction to the 1 + oxidation state for the nickel species), whereas SnCl₂ forms chlorine bridges with the transition metals.     

Hydrothermal and sonochemical synthesis of a nano-sized nickel(II) Schiff base complex as a precursor for nano-sized nickel(II) oxide; spectroscopic, catalytic and antibacterial properties

The Ni(II) complexes [Ni(L)₂](ClO₄)₂ (1) and [Ni(L)₂(NO₃)₂] (2), where L is the Schiff base ligand of 4,5,9,13,14-pentaaza-benzo[b] triphenylene, were synthesized and characterized by physico-chemical and spectroscopic methods. Nano-sized particles of (1) were prepared both by sonochemistry (3) and solvothermal (4) methods. NiO nanoparticles were obtained by calcination of the nano-structure complexes at 500 °C. The structures of the nano-sized compounds were characterized by X-ray powder diffraction and scanning electron microscopy. The thermal stabilities of the bulk complexes (1–2) and nano-sized particles (3–4) were studied by thermogravimetric and differential scanning calorimetry. The catalytic activities of complexes of (1–4) are reported. The free Schiff base and its Ni(II) complexes have been screened for antibacterial activities against three Gram-positive bacteria. The metal complexes are more active than the free Schiff base. Electrochemical studies show that the Ni complexes undergo irreversible reduction in MeCN solution.     

Magnetic and spectral studies on nickel(II) and copper(II) dithiocarbazates derived from isoniazid

Some isonicotinoyldithiocarbazate complexes of nickel(II) and copper(II), of general formulae M(IN-Dtcz)₂, [M(IN-DtczH)₂]Cl₂, and [M(IN-DtczH-Sal)₂]Cl₂ (M?=?Ni(II), Cu(II); INDtcz?=?isonicotinoyldithiocarbazate; IN-DtczH?=?isonicotinoyldithiocarbazic acid; IN-DtczH-Sal?=?salicylaldehyde Schiff base of isonicotinoyldithiocarbazic acid), have been synthesized. These complexes have been investigated by elemental analyses, mass, room temperature infrared and electronic spectra, and variable temperature magnetic susceptibility measurements. The three nickel(II) dithiocarbazates and [Cu(IN-DtczH-Sal)₂]Cl₂ exhibit NS linkage of the ligands, while Cu(IN-Dtcz)₂ and [Cu(IN-DtczH)₂]Cl₂ have ONS binding of the ligands. The nickel(II) dithiocarbazates have [NiN₂S₂] chromophore. Magnetic and solution electronic absorption spectral data reveal square-planar geometry for Ni(IN-Dtcz)₂ and the existence of square-planar–tetrahedral equilibrium for [Ni(IN-DtczH)₂]Cl₂ and [Ni(IN-DtczH-Sal)₂]Cl₂. Copper(II) dithiocarbazates, namely Cu(IN-Dtcz)₂, [Cu(IN-DtczH)₂]Cl₂, with ONS ligands having dimeric or polymeric octahedral structures, and [Cu(IN-DtczH-Sal)₂]Cl₂, with NS binding having dimeric square-planar structure, exhibit antiferromagnetism. Superexchange pathway involving the bridging nitrogen and sulfur of the isonicotinoyldithiocarbazate ligands rather than direct metal–metal exchange is suggested for antiferromagnetic interactions. The spin exchange parameter, ?2J?=?202.14 and 29.26?cm^?1, has been evaluated for [Cu(IN-DtczH)₂]Cl₂ and [Cu(IN-DtczH-Sal)₂]Cl₂, respectively, while it could not be evaluated for Cu(IN-Dtcz)₂ because the slope was negative due to the non-variation of its magnetic moment with temperature. The difference in antiferromagnetic behavior and inconsistency of 2J for [Cu(IN-DtczH-Sal)₂]Cl₂ has been attributed to different electronic and steric factors of the three ligands, that is, isonicotinoyldithiocarbazate, its acid, and salicylaldehyde Schiff-base derivative.     

Cobalt(II), nickel(II), and copper(II) complexes of 14-membered hexaazamacrocycles: synthesis and characterization

Cobalt(II), nickel(II), and copper(II) complexes containing 5,12-di(4-bromophenyl)-7,14-dimethyl-1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-dione (H₂L¹) and 5,12-diphenyl-7,14-dimethyl-1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-dione (H₂L²) have been synthesized. All complexes were characterized by elemental analysis, MALDI TOF-MS spectrometry, and electronic absorption spectroscopy. The crystal structures of two compounds, [Cu₂(H₂L¹)Cl₄]_n and [NiL²], were determined by X-ray powder diffraction. In the polymeric [Cu₂(H₂L¹)Cl₄]_n, the Cu₂Cl₄ units and H₂L¹ molecules are situated on inversion centers. Each Cu(II) has a distorted trigonal-bipyramidal coordination environment formed by N and O from H₂L¹ [Cu–N 2.340(14)?Å, Cu–O 1.952(11)?Å], two bridging chlorides [Cu–Cl 2.332(5), 2.279(5)?Å] and one terminal chloride [Cu–Cl 2.320(6)?Å]. In the [NiL²] complex, the Ni(II) situated on inversion center has a distorted square-planar coordination environment formed by four nitrogens from L² [Ni–N 1.860(11), 1.900(11)?Å].     

A new synthesis and the electrochemical behaviour of nickel(II) dithiophosphate and dithiophosphinate complexes

Summary The [Ni(S₂PR₂)₂] complexes (R=i-PrO, PhO, or Et) can be conveniently prepared by reaction of [Ni{P(OPh)₃}₄] with [R₂P(S)S]₂ (R=i-PrO, PhO, or Et) in refluxing CHCl₃. The electrochemical behaviour of the complexes in CH₂Cl₂ and MeCN has been studied by cyclic voltammetry and coulometry. The oxidation of complexes at a glassy carbon reveals an e.c. mechanism. The [Ni(S₂PR₂)₂] complexes undergo a one-electron irreversible reduction.     

Effective reduction of <Emphasis Type="Italic">p</Emphasis>-nitrophenol catalyzed by nickel(II) adamantane complexes

Two Ni(II) adamantane complexes, [Ni(bqad)Cl₂] (1) and [Ni(bpad)(dmbp)(H₂O)](ClO₄)₂·CH₃OH H₂O (2) (bqad = N,N′-bis(2-quinolinylmethyl) amantadine, bpad = N,N′-bis(2-pyridylmethyl)amantadine, dmbp = 5,5′-dimethyl-2,2′-bipyridine) have been synthesized and characterized by elemental analysis, infrared spectroscopy and single crystal X-ray diffraction. The nickel centers in complex 1 have a distorted tetragonal pyramidal geometry, while the coordination polyhedron of 2 can be described as a distorted octahedron. The reaction kinetics for reduction of p-nitrophenol to p-aminophenol catalyzed by these complexes has been investigated by UV–visible spectrophotometry. Complex 1 exhibits a higher turnover frequency of 1.4 min^?1 for the reduction of p-nitrophenol.     

Half-sandwich scorpionate nickel complexes with aliphatic dicarboxylic acid co-ligands

A series of new nickel complexes, namely [Tp*Ni(sub)]·EtOH (1), [Tp*Ni(ad)]·EtOH (2), [Tp*Ni(seb)(H₂O)] (3), and [Tp*Ni(μ–suc)NiTp*(MeOH)₂] (4) (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate, H₂sub = suberic acid, H₂ad = adipic acid, H₂seb = sebacic acid, H₂suc = succinic acid), were synthesized in mixed solvents at room temperature. The complexes were characterized by physico-chemical and spectroscopic methods. In addition, X-ray crystal structure analysis indicates that the four complexes share a common scorpionate (Tp*) Ni core with different aliphatic dicarboxylic acid ligands, and the nickel atom is in a distorted octahedral environment with the N₃O₃ donor set. Surface voltage spectroscopy indicates that these complexes exhibit surface photovoltage responses in the range of 300–800 nm, which can be assigned to LMCT and d → d ^* electronic transitions. In addition, quantum chemistry calculations on the complexes were performed and are discussed.     

Synthesis of nickel sulfide and nickel–iron sulfide nanoparticles from nickel dithiocarbamate complexes and their photocatalytic activities

[ Ni(dtc)₂] (dtc = N-(pyrrole-2-ylmethyl)-N-thiophenemethyldithiocarbamate ( 1 ), N-methylferrocenyl-N-(2-phenylethyl)dithiocarbamate ( 2 ), N-furfuryl-N-methylferrocenyldithiocarbamate ( 3 ), and (N-[pyrrole-2-ylmethyl]-N-thiophenemethyldithiocarbamato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II) ( 4 ) complexes were prepared and characterized by elemental analysis, infrared, ultraviolet–visible, and nuclear magnetic resonance (¹H and ¹³C) spectroscopies. The data were consistent with the formation of square planar nickel(II) complexes, which was confirmed by single-crystal X-ray diffraction studies on 2 and 4 . Fe···Fe interactions exhibited by complex 2 led to supramolecular aggregation. The structure of 4 reveals intermolecular and intramolecular C-H···Ni anagostic interactions. The anion-sensing properties of 2 were studied with halide ions by cyclic voltammetry. It was observed that 2 acts as sensor for bromide. Complexes 1 , 2 , and 3 , were utilized to prepare nickel sulfide, nickel–iron sulfide-1, and nickel–iron sulfide-2, respectively. The composition, structure, morphology, and optical properties of nickel sulfide and nickel–iron sulfides were examined using powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, ultraviolet–visible, fluorescence, and infrared spectroscopy. Powder X-ray diffraction patterns of nickel sulfide, nickel–iron sulfide-1, and nickel–iron sulfide-2 indicate the formation of orthorhombic Ni₉S₈, cubic NiFeS₂, and cubic Ni₂FeS₄, respectively. The photocatalytic activities of as-prepared nickel sulfide and nickel–iron sulfide-1 nanoparticles were investigated for photodegradation of methylene blue and rhodamine-B under ultraviolet irradiation. Nickel–iron sulfide-1 nanoparticles show slightly higher photodegradation efficiency compared with the nickel sulfide nanoparticles.     

Tetrathiomolybdates of nickel

Summary The complexes [Ni(en)₃]MoS₄, [Ni(dien)₂]MoS₄ and [Ni(phen)₂(MoS₄)]·2H₂O (en = ethylenediamine, dien = diethylenetriamine, phen = 1,10-phenanthroline) were prepared. On the basis of their magnetochemical and spectral properties the compounds can be characterized as octahedral nickel(II) complexes. The complexes were also studied by c.v. Chemical oxidation of [Ni(en)₃]MoS₄ affords [Ni(en)MoS₄]₂SO₄; this complex has been characterized by i.r. and e.p.r. spectroscopy and by magnetic measurements.     

Synthesis,characterization, and anticancer activity of some azole‐heterocyclic complexes with gold(III), palladium(II), nickel(II), and copper(II) metal ions

Four new complexes of Au(III), Pd(II), Ni(II), and Cu(II) ions were synthesized, derived from a novel heterocyclic ligand (L) that has both triazole and tetrazole rings. The ligand synthesis was through successive steps to achieve both heterocyclic rings. The synthesized compounds were characterized using conventional techniques like infrared, ultra violet—visible and proton/carbon nuclear magnetic resonance spectroscopy, metal and thermal analyses, and molar conductivity. All complexes were suggested to have square planar geometry, gold, nickel, and palladium complexes were salts while copper neutral complexes have the chemical formulas; [AuL₂]Cl.2H₂O, [PdL₂]Cl₂.2H₂O, [NiL₂]Cl₂.2H₂O, and [CuL₂]. The cytotoxic effect was studied on breast cancer cell line (MCF‐7 cell line) at different concentrations by using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay method, for the ligand (L) and complexes. The results showed that gold(III) and nickel(II) complexes have the highest cytotoxicity among all compounds against cancer cell lines.     

Spectral, thermal, and X-ray studies on some new bis and tris-hydrazine and hydrazinium metal pyruvates

Some bis-hydrazine metal pyruvates of transition metal ions of the formula M[CH₃COCOO]₂ [N₂H₄]₂, where M = Co, Ni, Zn or Cd, tris-hydrazine metal pyruvates of the formula M[CH₃COCOO]₂ [N₂H₄]₃, where M = Co, Ni, Zn or Cd, and hydrazinium metal pyruvates [N₂H₅]₂M[CH₃COCOO]₄, where M = Co or Ni have been prepared and the compositions of the complexes have been determined by chemical analysis. The magnetic moments and electronic spectra of the complexes suggest a high-spin octahedral geometry for them. Infrared spectral data of bis-hydrazine complexes indicate the bidentate bridging mode shown by hydrazine molecules and mono dentate coordination by pyruvate ions. However, in tris-hydrazine complexes the pyruvate ions are ionic in nature. In hydrazinium complexes two hydrazinium ions and four pyruvate ions show unidentate coordination mode resulting in six coordination around metal ions. Thermo gravimetry and differential thermal analysis in air reveal that most of the complexes decompose in one step to give the respective metal carbonate as the final residue. However, the hydrazinium complexes yield Co₂O₃ or NiO as the residue. The final residues were identified by their X-ray powder data. The X-ray powder diffraction patterns of each series of complexes reveal isomorphism among the series.     

Electroanalytical investigation on the stability of tetracoordinate nickel(I) complexes

The stability of tetracoordinate nickel(I) complexes, of the type [Ni(CN)₂P₂]^? (P=substituted phosphine), generated by cathodic reduction of the parent nickel(II) complexes, has been studied by cyclic voltammetry and double potential step techniques. Evidence has been obtained that nickel(I) complexes decay to the dimeric species Ni₂(CN)₂P₄ via a first order chemical reaction the rate determining step being the release of a cyanide ion leading to the radical species [Ni(CN)P₂]. The experimental trend obtained for the first order kinetic constants has been explained on the basis of the different “trans-effect” induced by a cyanide ligand in comparison with that induced by a phosphine group and taking into account the different basic character of the phosphine ligands.     

Thermal,spectral and magnetic studies on glycine complexes of cobalt(II), nickel(II) and zinc(II) with hydrazine

Hydrazinium metal glycinates [(N₂H_{5 2}M(NH₂CH₂COO)₄] and bis(hydrazine)metal glycinates, [M(NH₂CH₂COO)₂(N₂H₄)₂], whereM=Co, Ni or Zn have been prepared and characterized by chemical analyses, magnetic moments and vibrational and electronic spectra. The thermal behaviour of these compounds has been studied by thermogravimetry and differential thermal analyses. These complexes decompose with high exothermicity giving metal powder as the final residue. The X-ray powder data of each set of complexes show isomorphism among themselves.     

含有NH2CH2CH2CH2NH2和o-C6H4(NH2)2配体的镍配合物的合成、结构和它们在乙烯聚合中的作用

两种镍的配合物[Ni(NH2CH2CH2CH2NH2)3]Cl2 (1)和[Ni(C6H4N2H4)2Cl2] (2)已经被合成并且通过红外和单晶X射线衍射分析对其进行了表征。在配合物1中,镍原子处于手性假八面体[NiN6]的几何构型中,它与三个1,3-丙二胺分子形成了三个六元环。在配合物2中,镍原子除了与两个o-苯二胺分子通过四个Ni-N键形成两个五元环外,它还与两个Cl原子配位形成了反式Ni-Cl2,这不同于以往报道过的镍的二胺配合物。这两个镍的配合物被MAO, MMAO或Et2AlCl活化后,对乙烯的二聚合或三聚合显示了很好的催化活性[对于配合物2,催化活性达到3.59×106 g mol-1 (Ni) h-1]。     

Transition Metal Complexes with the Thiosemicarbazide-based ligands. XII. Complexes of nickel(II) with benzoylacetone S-methylisothiosemicarbazone and N(1)-2-butylidene-4-oxo-4-phenyl-N(4)-salicylidene-S-methylisothiosemicarbazide

A template synthesis procedure yielded [Ni(HL¹)NH₃]I, where HL¹ is the monoanion of the terdentate ONN benzoylacetone S-methylisothiosemicarbazone ligand. The reaction of this complex with an excess of NH₄NCS, pyridine, or hydrazine resulted in the complexes [Ni(HL¹)(NH₃)NCS] and [Ni(L¹)A] (A = Py, N₂H₄). The monoanionic form of the ligand is obtained by deprotonation of the enolic form of the benzoylacetone moiety, whereas the dianion is formed by additional deprotonation of the terminal NH₂ group. Finally, the reaction of [Ni(HL¹)NH₃]I with salicyladehyde produced the NiL² complex in which L² stands for the dianion of the ONNO ligand N(1)-2-butylidene-4-oxo-4-phenyl-N(4)-salicylidene-S-methylisothiosemicarbazide. All complexes are diamagnetic and have a square-planar configuration, except for [Ni(HL¹)(NH₃)NCS], for which te data of i.r. spectra suggest a square-pyramidal structure. The electronic absorption spectra of the ethanolic solutions of all complexes are characteristic of typical square-planar coordination of nickel(II).     

Synthesis,crystal structure and DFT calculations of octahedral nickel(II) complexes derived from N′-[(E)-phenyl(pyridin-2-yl)methylidene]benzohydrazide

The two new nickel(II) complexes, [Ni(HL)(L)](NO₃)?H₂O (1) and [Ni(L)₂] (2) (where HL/L = N′-[(E)-phenyl(pyridin-2-yl)methylidene]benzohydrazide), have been synthesized and characterized by elemental analysis, spectroscopic, magnetic susceptibility, and cyclic voltammetric measurements. Single-crystal X-ray analysis of [Ni(HL)(L)](NO₃)?H₂O (1) and [Ni(L)₂] (2) has revealed the presence of a distorted octahedral geometry around nickel(II). The X-ray and spectral characterizations have confirmed the existence of the keto-enol form of the ligands in the complexes. The electronic structures and spectral properties of the ligands and the complexes have been explained by DFT and TDDFT calculations. Superoxide dismutase activity of these complexes has also been measured.     

Bimetallic Au–Ni Nanoparticles Embedded in SiO2 Nanospheres: Synergetic Catalysis in Hydrolytic Dehydrogenation of Ammonia Borane

Gold–nickel nanoparticles (NPs) of 3–4 nm diameter embedded in silica nanospheres of around 15 nm have been prepared by using [Au(en)₂Cl₃] and [Ni(NH₃)₆Cl₂] as precursors in a NP‐5/cyclohexane reversed‐micelle system, and by in situ reduction in an aqueous solution of NaBH₄/NH₃BH₃. Compared with monometallic Au@SiO₂ and Ni@SiO₂, the as‐synthesized Au–Ni@SiO₂ catalyst shows higher catalytic activity and better durability in the hydrolysis of ammonia borane, generating a nearly stoichiometric amount of hydrogen. During the generation of H₂, the synergy effect between gold and nickel is apparent: The nickel species stabilizes the gold NPs and the existence of gold helps to improve the catalytic activity and durability of the nickel NPs.     

Thermal square planar-to-octahedral transformation of nickel(II) complexes containing butanediamines in a solid phase

Thermal reactions of the nickel(II) complexes, [Ni(m-bn or i-bn)₂]X₂ and [Ni(H₂O)₂(dl-bn)₂]X₂·n H₂O, where m-bn, i-bn, and dl-bn are meso-2,3-butanediamine, 2-methyl-1,2-propanediamine, and dl-2,3-butanediamine, respectively, X is Cl^?, Br^?, I^?, NO^?₃, or ClO^?₄, and n is 2 for bromide, and 0 for the others, were investigated in a solid phase before and after heating using thermal analyses (TG and DSC) and spectral and magnetic measurements. In the case of the chloride and bromide, the square planar bis(dl-bn) complexes obtained by dehydration of the respective diaqua complexes were transformed to the octahedral diacido bis(dl-bn) complexes upon further heating. The same structural transformation was observed in the thermal reactions of [Ni(m-bn)₂](NO₃)₂ and [Ni(i-bn)₂]Cl₂. It was summarily recognized that such square planar-to-octahedral transformation was favored in the order dl-bn > i-bn > m-bn complexes in the respective halides, and it was a reversible thermochromism from yellow to blue. The changes in enthalpy of the reactions were endothermic and fell in the range of about 10–20 kJ mole^?1. The possibility of such configurational change seems to be dependent mainly upon the ionic radius of the X anion, the orientation of two C-substituted methyl groups on butanediamines in the formation of the complexes, and the thermal stability of the complexes themselves.     

Synthesis and Characterization of Homoleptic and Heteroleptic Complexes Involving Dithiocarbamates,Triphenylphosphine, and Nickel(II)

Abstract

Six new nickel complexes of two dithiocarbamate ligands (cyfdtc = N-cyclohexyl-N- furfuryldithiocarbamate and bztpedtc = N-benzyl-N-[2-thiophenylethyl]dithiocarbamate) namely, (Ni[cyfdtc]₂) (1), (Ni[bztpedtc]₂) (2), (Ni[cyfdtc][NCS][PPh₃]) (3), (Ni[bztpedtc] [NCS][PPh₃]) (4), (Ni[cyfdtc][PPh₃]₂)ClO₄ (5), and (Ni[bztpedtc][PPh₃]₂)ClO₄ (6) have been prepared and characterized using IR, electronic, and NMR (¹H and ¹³C) spectra. A single crystal X-ray structural analysis was carried out for complex 3 and showed that nickel is in a distorted square planar arrangement with the NiS₂PN chromophore. The shift in ν_C?N of the heteroleptic complexes to higher frequencies compared with the parent complex is assigned to mesomeric delocalization of electron density from the

dithiocarbamate ligand toward the metal atom, which increases the contribution of polar thioureide form in mixed ligand complexes. Electronic spectral studies suggest square planar geometry for the complexes. In the ¹³C NMR spectra, the upfield shift of NCS₂ carbon signal for 3 and 4 from the chemical shift value of 1 and 2 is due to effect of PPh₃ on the mesomeric drift of electron density toward nickel throughout thioureide C?N bond.