Nickel Bromide Research Articles

Tailoring polyethylenes through constraining geometry of nickel complex: Synthesis, characterization and ethylene polymerization of 8-(2-benzhydrylnaphthylimino)-5,6,7-trihydroquinolylnickel halides

The newly prepared 8-(2-benzhydrylnaphthylimino)-5,6,7-trihydroquinoline derivatives (L1–L3) individually reacted with (DME)NiBr2 or NiCl2 to form their corresponding nickel bromide complexes (Ni1–Ni3) and nickel chloride complexes (Ni4–Ni6). These nickel complexes were fully characterized by FT-IR spectroscopy and elemental analysis as well as single crystal X-ray analysis. The representative molecular structures of Ni1 and Ni4, confirmed by single crystal X-ray diffraction, revealed a distorted octahedral geometry around nickel atom as the halo-bridged centro-symmetric dimers with formulae as L2Ni2X4 (X=Br, Ni1–Ni3; X=Cl, Ni4–Ni6). All nickel complexes, activated with either modified methylaluminoxane (MMAO) or diethylaluminiumchloride (Et2AlCl), exhibited high activities toward ethylene polymerization, producing branched polyethylene with low molecular weights. The obtained polyethylenes showed tail peaks in the high molecular weight portion according to the GPC curves due to the constrained geometry caused by the bulky 2-benzhydrylnaphthyl-substituted 8-arylimino-5,6,7-trihydroquinoline derivatives.

Nickel(II) α-diimine catalysts with carboxyl groups for ethylene oligomerization and polymerization

A series of nickel(II) α-diimine complexes with strong electron-withdrawing carboxyl groups, having reactive hydrogen atoms, were prepared and used as precatalysts for ethylene oligomerization and/or polymerization. The influence of metal halides and ligand structure on the catalytic activity and properties of products was investigated. The results showed that nickel bromide was much more active than nickel chloride, and the substituents at the ortho-position of aryl ring had large influence on the properties of products. Therefore, the products ranging from liquid oligomers to polymers could be readily obtained by the variation of the substituents on the ligands and reaction conditions.

Multi-walled carbon nanotubes as a ligand in nickel α-diimine based ethylene polymerization

Two novel heterogeneous nickel α-diimine based polymerization catalysts, containing MWCNT as the main ligand, were synthesized by novel in situ catalyst preparation technique. The in situ synthesis was performed by covalent attachment of the acenaphthenic ligand core to amine functionalized MWCNT ligand arms through diimine bonding and further nickel dibromide chelation. The prepared catalysts were fully characterized and their structures and supporting efficiencies were determined. Single or double introduction of the MWCNTs through their ends or sidewall(s) in the catalytic system, as a ligand, influenced the catalytic performance, microstructure and morphology of obtained polyethylenes. MWCNT sidewall bonding to para-aryl position of the tetramethylphenyl moiety performed as more electron-donating ligand than MWCNT ends linked to the imine bond and protected the catalytic system to retain its activity. This character resulted in the maintenance of the resulting polymer topology at elevated temperatures so that the catalytic activity and the obtained polymer melting points remained around 110 g PE∙mmol−1 Ni∙h−1 and 123 °C in all polymerization temperatures respectively. In polymerization trials, molecular weight fall against temperature was not as sharp as what had been observed in sequentially prepared catalysts insofar as the molecular weight of resultant polymer at 60 °C reached to 310000 g∙mol−1 which was close to the highest value had been reported at 30 °C for sequentially prepared catalysts. TEM observations showed the presence of the stopped-growth polymer chains due to geometrical constrains or ligand debonding for both catalytic systems.

A low-symmetry nickel(II) α-diimine complex for homopolymerization of ethylene: study of interactive effects of polymerization parameters

A low-symmetry nickel(II) α-diimine complex [(2,4,6-trimethylphenyl)imino)-((2,6-diisopropylphenyl)imino)-acenaphthene nickel(II) dibromide] (C1) was synthesized and characterized crystallographically. Response surface method (RSM) was employed to study the interactive effects of critical factors on ethylene polymerization. The maximum activity of C1, when activated by methylaluminoxane (MAO) cocatalyst {4960 kgPE [(mol Ni)−1 h−1]} was achieved at 10 °C, 7 bar and CC (cocatalyst-to-catalyst ratio) equal to 1550, which is higher than most similar counterparts. Considering surface plots of MW, it is concluded that at high levels (>1000) of CC, there is competition between chain transfer to aluminum and reinsertion of macromonomer to newly formed metal-methyl bonds.

Cobalt(II), nickel(II), and copper(II) bromide complexes with 3-amino-4-ethoxycarbonylpyrazole: Syntheses, structures, and magnetic properties

New complexes of cobalt(II), nickel(II), and copper(II) bromides with 3-amino-4-ethoxycarbo- nylpyrazole (L) of the composition ML4Br2 · 2H2O (M = Co(II) and Ni(II)) and CuL2Br2 are synthesized. The compounds are studied by X-ray diffraction analysis (CIF files CCDC nos. 1006284 (I), 1006286 (II), and 1006285 (III)), IR spectroscopy, and static magnetic susceptibility. In the complexes, the metal ions are in the distorted octahedral environment and the ligand is coordinated to the metal by the N(2) atom of the pyrazole cycle according to the monodentate mode. The Co(II) and Ni(II) complexes are mononuclear, whereas CuL2Br2 is polynuclear due to the bridging function of the bromide ion. Complex CuL2Br2 possesses the thermochromic properties: the transition of the color is brown (at room temperature) ⇔ light brown (at the temperature of liquid nitrogen).

Nickel(II) Complexes Bearing 4-Arylimino-1,2,3-trihydroacridines: Synthesis, Characterization, and Ethylene Oligomerization.

Nickel(II) complexes have attracted much attention as a new generation of olefin catalysts since the α-diiminonickel complex was discovered as a highly efficient procatalyst for ethylene polymerization. A series of novel 4-arylimino-1,2,3-trihydroacridylnickel(II) dihalide complexes was synthesized in a one-pot reaction of 2,3-dihydroacridine-4-one and different anilines with nickel(II) chloride or nickel(II) bromide 1,2-dimethoxyethane complex. The complexes were characterized by infrared spectroscopy and elemental analysis. The molecular structures of the representative complexes 4-(2,6-diisopropylphenylimino)-1,2,3-trihydroacridylnickel(II) dichloride (C3), 4-(2,4,6-trimethylphenylimino)-1,2,3-trihydroacridylnickel dichloride(II) (C4), and 4-(2,4,6-trimethylphenylimino)-1,2,3-trihydroacridylnickel(II) dibromide (C9) were confirmed by single-crystal X-ray crystallography, revealing a distorted tetrahedral geometry around the nickel(II) of C3 and distorted trigonal bipyramidal geometry for C4 and C9. With the activation of trimethylaluminium (TMA), all nickel(II) complexes exhibited good activity for ethylene oligomerization, and oligomer products ranged from butene (C4) to hexadecene (C16).

Raman Spectroscopy Study of the Doping Effect of the Encapsulated Iron, Cobalt, and Nickel Bromides on Single-Walled Carbon Nanotubes

In this contribution the modification of the electronic properties of single-walled carbon nanotubes (SWCNTs) filled with nickel bromide, cobalt bromide, and iron bromide was studied by Raman spectroscopy. The doping-induced alterations of the radial breathing mode (RBM) and G-mode in the Raman spectra of the filled SWCNTs were analyzed in detail. The observed shifts of the components of the Raman modes and changes of their profiles allowed concluding that the embedded compounds have an acceptor doping effect on the SWCNTs, and the doping level increases in the line with nickel bromide-cobalt bromide-iron bromide.

Tailoring Polyethylenes by Nickel Complexes Bearing Modified 1-(2-Benzhydrylnaphthylimino)-2-phenyliminoacenaphthylene Derivatives

A series of 1-(2-benzhydrylnaphthylimino)-2-phenyliminoacenaphthylene derivatives (L1–L5) was synthesized, characterized, and then reacted with (DME)NiBr2 to form the corresponding [1-(2-benzhydrylnaphthylimino)-2-phenyliminoacenaphthyl]nickel bromides (C1–C5). All nickel complexes were fully characterized by their FT-IR spectra and elemental analysis. The molecular structures of the representative complexes C1 and C4 were also determined by single-crystal X-ray diffraction. On activation with either methylaluminoxane (MAO) or diethylaluminum chloride (Et2AlCl), all title nickel complexes showed high activities toward ethylene polymerization; the resulting polyethylenes showed molecular weights higher than those obtained by using the nickel analogues bearing (2-benzhydrylnaphthylimino)pyridines and also had branches lower than those obtained by using other diiminoacenaphthylnickel analogues. Therefore, the modification of ligands could affect the catalytic behavior of their nickel complexes in order to tailor the molecular weights and branches of the resulting polyethylenes.

Studies on optical, mechanical, dielectric properties of bisthiourea nickel bromide NLO single crystal

Bisthiourea nickel bromide (BTNB) single crystal has been grown by solution growth technique at room temperature. The crystal structure and lattice parameters were determined for the grown crystal by single crystal X-ray diffraction studies. Optical constants like band gap, refractive index, reflectance, extinction coefficient and electric susceptibility were determined from UV–vis-NIR spectrum. Nonlinear optical property was discussed to confirm the SHG efficiency of the grown crystal. The mechanical strength of the grown crystal was analyzed using Vickers microhardness tester. The dielectric constant and dielectric loss of bisthiourea nickel bromide are measured in the frequency range of 50Hz to 5MHz at different temperatures. The ac conductivity studies were carried out on bisthiourea nickel bromide crystals. In order to investigate the growth mechanism and surface features, etching studies are carried out for the crystal. Photoconductivity studies were carried out on bisthiourea nickel bromide crystals.

Carbene oligomerization promoted by nickelocene derived complexes

New catalytic systems based on nickelocene were used as initiators in polymerization of ethyl acetate carbene derived from ethyl diazoacetate. Nickelocene itself and nickelocene activated with n-butyllithium or diphenylmethyllithium led to the formation of oligomers with average molecular weight about 800Da. η5-Cyclopentadienyl(1,3-diallyl-imidazolin-2-ylidene)nickel bromide activated with an excess of methylalumoxane gave ethyl acetate carbene polymer with average molecular weight 21,800Da. MALDI TOF spectra indicate coordination–insertion mechanism of polymerization in all catalytic systems applied.

Controlled Living Polymerization of Carbodiimides Using Versatile, Air-Stable Nickel(II) Initiators: Facile Incorporation of Helical, Rod-like Materials

The new polymerization of carbodiimides using two, simple [bis(triphenylphosphino)aryl]nickel(II) bromide complexes has been discovered to occur in a controlled, living fashion. These initiators are substantially more air and moisture stable compared to their titanium(IV) counterparts making them significantly easier to synthesize, purify, and utilize. The polymerization is initiated via aryl ligand transfer to the electrophilic center carbon of the carbodiimide. Sequential insertions of the carbodiimide π-bond into the nickel–nitrogen amidinate coordination bond propagates the polymer chain in a living chain growth manner as evident by the linear relationship in the plots of percent conversion vs Mn, ln([M]o/[M]) vs time, and monomer: initiator ratio vs Mn. The transferred aryl ligand was confirmed to be appended to the terminus of the polymer chain by MALDI–TOF and 19F NMR. This added control element offers new opportunities to end functionalize rigid-rod, helical polycarbodiimides. This new technique a...

Enhancing α-Diimine Catalysts for High-Temperature Ethylene Polymerization

Sterically demanding 2,6-bis(diphenylmethyl)-4-methylaniline was condensed onto acenaphthenequinone via an aminoalane intermediate and metalated using nickel(II) dibromide dimethoxyethane adduct to yield bis[(2,6-dibenzhydryl-4-methylimino) acenaphthene]dibromo nickel(II). This α-diimine precatalyst was examined for high-temperature ethylene polymerization and proved to be thermally robust at temperatures as high as 90 °C, demonstrating enhanced activity as compared with related catalysts. Furthermore, the resultant polymers displayed increased melting transitions as compared with those produced using catalysts with identical N-aryl moieties appended to nonacenaphthenequinone-derived ligand backbones.

Three-coordinate nickel(II) and nickel(I) thiolate complexes based on the β-diketiminate ligand system.

Mononuclear nickel(II) thiolate complexes [L(tBu)Ni(SEt)] (1) and [L(tBu)Ni(aet)] (2, aet = (-)S(CH2)2NH2) (L(tBu) = [HC(C((t)Bu)NC6H3((i)Pr)2)2](-)), supported by a bulky nacnac ligand, were synthesized by treatment of the nickel(II) bromide precursor [L(tBu)Ni(Br)] (I) with the potassium salts of ethanethiol and cysteamine, respectively. The nickel atom in 1 features a planar T-shaped environment, while the Ni ion within 2 shows a distorted square planar coordination geometry, as the aminoethanethiolate (aet) is coordinated as a chelating ligand. In 2 the β-diketiminate ligand binds in a rarely observed κ(2)C,N coordination mode. Reduction of complex 1 or its benzenethiolate analogue [L(tBu)Ni(SPh)] (II) by KC8 resulted in the formation of dinuclear Ni(I) thiolates (K·OEt2)(K)[L(tBu)Ni(SEt)]2 (3) and (K·OEt2)2[L(tBu)Ni(SPh)]2 (4), respectively. In these compounds [L(tBu)Ni(SR)](-) units are held together by potassium cations produced in the reduction process. All compounds mentioned were structurally characterized by single-crystal X-ray crystallography.

New ionic fluorenylnickel complexes: Synthesis and solid state structure

New fluorenylnickel complexes [M(THF)n]+[Ni(η5-Flu)(η1-Flu)2]− (M = +48 Li, 1 and M = Na, 2) have been obtained in the reaction of nickel bromide with fluorenyllithium and -sodium. The X-ray molecular structures of 1 (monoclinic; P21/c) and 2 (orthorhombic; Fdd2) reveal that in both complexes two fluorenyl ligands are bonded to the nickel atom by η1 bond and the third one is bonded to the nickel atom by η5 bond. Complexes 1 and 2 are the first structurally characterized nickel complexes bearing fluorenyl ligands.

Effects of mixing metal ions for the thermal runaway reaction of TMCH

1,1-bis(tert-Butylperoxy)-3,3,5-trimethylcyclohexane (TMCH) is commonly used as a crosslinking agent or an initiator of the heat-curing agent for polybutadiene rubber. Metal ions that remain in the pipelines or containers of manufacturing processes may affect the thermal stability of the organic peroxides. Moreover, pipelines or metal containers may contain some metal ions because of inner corrosive chemicals or surface deterioration, which may induce a chemical reaction, while TMCH is mixed with them. To avoid these unexpected chemical reactions, we focused on the thermal hazard analysis of TMCH mixed with metal ions, such as nickel(II) bromide or copper(II) bromide. The experiments can determine thermokinetic parameters, including exothermic onset temperature (T 0), maximum temperature (T max), and heat of decomposition (ΔH d), under non-isothermal conditions by differential scanning calorimetry. Non-isothermal experimental results combined with isoconversional kinetic analysis can acquire further safety parameters, such as apparent activation energy (E a) and time to maximum heating rate. The results of this study could be used as a proactive case for the storage of TMCH mixed with metal ions.

New supramolecular synthons based on 3d transition metal complexes with bidentate bispidines: synthesis and structural, spectroscopic, and electrochemical studies

A new supramolecular synthon, a 2L: 1M complex of bidentate bispidine with transition metal, was suggested. A number of complex compounds of 1,5-dimethylbispidin-9-one with Cu ii , Ni ii , and Co ii salts (perchlorates, chlorides, bromides, nitrates, trifluoroacetates) were synthesized. The structure and composition of complexes obtained were estimated based on the combination of physicochemical methods of analysis (elemental analysis, X-ray diffraction analysis, NMR, IR, and Raman spectroscopy, electron absorption spectroscopy, ESI mass spectrometry, CVA). The composition of most complexes in the solid state corresponds to the formula ML2X2, and in a number of cases the fragment [ML2]2+ is retained in solution, which was shown by NMR spectroscopy for nickel complexes and by mass spectrometry for copper complexes. In the case of copper chloride, the composition of the acetonitrile solutions in the presence of the ligand depends on the ratio of starting compounds and their concentration: an increase in proportion of CuCl2 and concentration shifts the equilibrium to the side of complexes with higher nuclearity. A 2L: 1M complex of bispidine with metal was for the first time structurally characterized using copper(ii) nitrate derivative as an example. The CVA method showed existence of reversible electrochemical reduction of the metal for a number of complexes (the products of the reaction of 1,5-dimethylbispidin-9-one with nickel(ii) and cobalt(ii) chlorides, as well as with nickel(ii) bromide). According to the IR and Raman spectra, chelation of metals with 1,5-dimethylbispidin-9-one leads to the shift of the absorption band of the ligand carbonyl group from 1700 to 1721–1744 cm−1. Nickel(ii) and copper(ii) perchlorates and nitrates were concluded to be the most promising complexation agents for the binding of two NH,NH-bispidine ligands in a coordination polymer.

Electrochemical behavior of nickel bis-(2,6-diisopropylphenyl)diazobutadiene-1,4 dibromide in an aprotic solvent

The electrochemical behavior of bis-(2,6-diisopropylphenyl)diazobutadiene-1,4 and its nickel dibromide complex on dropping mercury and glassy carbon electrodes in an aprotic solvent was studied by AC polarography and cyclic voltammetry. Both the ligand and the nickel ion complex were shown to undergo electroreduction. The electrochemical reduction of nickel bis-(2,6-diisopropylphenyl)diazobutadiene-1,4 dibromide occurred stepwise and formed intermediate nickel(I) species.

2-{2,6-Bis[bis(4-fluorophenyl)methyl]-4-chlorophenylimino}-3-aryliminobutylnickel(II) bromide complexes: Synthesis, characterization, and investigation of their catalytic behavior

The series of 2-{2,6-bis[di(4-fluorophenyl)methyl]-4-chlorophenylimino}-3-aryliminobutane derivatives (L1–L5) and their nickel(II) dibromide complexes (Ni1–Ni5) were synthesized, and all organic compounds were fully characterized by the Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy and by elemental analysis, while the nickel complexes were characterized by FT-IR spectroscopy, elemental analysis, as well as by single-crystal X-ray diffraction for two representative examples, namely Ni1 and Ni4. A distorted tetrahedral geometry was observed for these four-coordinate nickel complexes. Upon the activation with either Methylaluminoxane or modified methylaluminoxane as co-catalyst, all nickel complex precatalysts showed very high activity toward ethylene polymerization with activities of up to 107 g(PE)·mol−1(Ni)·h−1, and afforded highly branched polyethylene with a bimodal distribution.

Ionic liquids for solid-state electrolytes and electrosynthesis

The aim of this work was to demonstrate that ionic liquids (ILs) as electrolytes for several applications have been explored. We have explored their potential as solvent-free electrolytes dispersed in natural polymer matrix and as electrolytes for electrosynthesis. The ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate ([C2mim][C2SO4]) was dispersed in gelatin and agar, producing free-standing-electrolyte membranes thermally stable up to 200°C and an ionic conductivity of 9.73×10−5Scm−1 at 30°C and 2.37×10−3Scm−1 at 100°C for Gelatin[C2mim][C2SO4] and 1.10×10−5Scm−1 at 30°C and 7.24×10−4Scm−1 at 100°C for Agar[C2mim][C2SO4] films. These samples were then tested in electrochromic devices (ECDs) revealing electrochemical reversibility during more than 200 color/bleaching cycles. Moreover, the electrochemical behavior of (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane)nickel(II) bromide, [Ni(tmc)]Br2, at a glassy carbon electrode in the absence and in the presence of unsaturated halides in the ionic liquids, [C2mim][C2SO4] and N,N,N-trimethyl-N-(2-hydroxyethyl) ammonium bis(trifluoromethylsulfonyl)imide ([N1 1 1 2(OH)][NTf2]), has been examined by cyclic voltammetry. It was observed that [Ni(tmc)]2+ complex was reduced in a reversible one-electron step and the electrogenerated [Ni(tmc)]+ complex catalytically reduced the carbon–halogen bond of unsaturated halides. The obtained results showed that the investigated ionic liquids are good candidates for use as electrolytes in either solid or liquid form.

Distinct new catalysts for utilization of ethylene gas to polymer and oligomer

Bi-nickel-center catalysts were prepared by Schiff-base condensation of 2,3-butanedione with 2,6-di-isopropylaniline; 2-5-butylaniline, 2-isopropylaniline and 1,4-phenylene diamine(I). More Schiff-base ligands were prepared by condensation of 2,3-butandione with 2,6-diisopropylaniline; 2,4-6-trimethyl aniline and 4,4-diaminophenyl (benzidine)(II), and subsequent metathesis reaction with (DME)NiBr2. Bis(alpha diimine)nickel(II)dibromide complexes are suitable catalysts and are precursors for the polymerization of ethylene after activation with methylaluminoxane (MAO). In comparison with these complex analogs, mono-nickel-center catalysts, the new catalysts have much bigger molecules, illustrated by the distance between every two active centers (II and III). For bi-nickel-center catalysts, the catalyst’s structural credibility had profound influence on the catalytic activity. When the substituent was diisopropyl; t-butyl or methyl, the catalysts demonstrated much higher catalytic activity than the corresponding mono-nickel-center catalysts. Catalyst (II) with phenyl bridge showed high activity compared with catalyst (III) with diphenyl bridge. The catalytic properties of these complexes and the character of the obtained polymers depend on the ligand structure of the used catalysts. Substituents on the arene moiety and/or the backbone of the ligand influence the polymerization reaction. Small aryl substituents result in the formation of low molecular weight oligomers, whereas bulky aryl substituents gave high molecular weight polyethylene. Catalysts are cheap and can be prepared easily with available starting material and stable in air. The effect of Al/Ni ratio, of reaction time, variation of ethylene pressure, and the effect of temperature on catalyst performance will be discussed.