Nickel Complexes (nickel + complex)

Distribution by Scientific Domains
Distribution within Chemistry


Selected Abstracts


Asymmetric Cyclization of ,-Formyl-1,3-dienes Catalyzed by a Zerovalent Nickel Complex in the Presence of Silanes.

CHEMINFORM, Issue 20 2003
Yoshihiro Sato
Abstract For Abstract see ChemInform Abstract in Full Text. [source]


Nickel Complexes of N/O -Functionalized N-Heterocyclic Carbenes as Precatalysts for Michael Reactions in Air at Room Temperature Under the Much Preferred Base-Free Conditions

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2009
Sriparna Ray
Abstract A series of several new nickel precatalysts supported overN/O -functionalized N-heterocyclic carbenes (NHC) for the Michael reactions of ,-dicarbonyl, ,-keto ester, ,-diester, and ,-cyano ester compounds with ,,,-unsaturated carbonyl compounds in air at ambient temperature under the much preferred base-free conditions are reported. Specifically, the nickel complexes, [1-(R1 -aminocarbonylmethyl)-3-R2 -imidazol-2-ylidene]2Ni [R1 = 2-C6H4(OMe); R2 = Me (1b), iPr (2b), CH2Ph (3b) and R1 = 2-CH2C4H3O; R2 = Me (4b), CH2Ph (5b)] carried out the highly convenient base-free Michael addition of the activated C,H compounds across ,,,-unsaturated carbonyl compounds in air at room temperature. The complexes 1b,5b were synthesized by the direct reaction of the respective imidazolium chloride salt with NiCl2·6H2O in CH3CN in the presence of K2CO3 as a base. The exceptional stability of 1b,5b has been attributed to the deeply buried nickel,NHC ,-bonding molecular orbitals as evidenced from the density functional theory (DFT) studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


Nickel Complexes and Cobalt Coordination Polymers with Organochalcogen (S, Se) Ligands Bearing an N -Methylimidazole Moiety: Syntheses, Structures, and Properties,

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2008
Wei-Guo Jia
Abstract The organochalcogen ligands (S, Se) derived from 3-methylimidazole-2-thione/selone groups mbit (2a), mbis (2b), ebit (2c), and ebis (2d) [mbit = 1,1,-methylenebis(1,3-dihydro-3-methyl-2H -imidazole-2-thione), mbis = 1,1,-methylenebis(1,3-dihydro-3-methyl-2H -imidazole-2-selone), ebit = 1,1,-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H -imidazole-2-thione), ebis = 1,1,-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H -imidazole-2-selone)] were synthesized and characterized. Mononuclear NiII complexes NiBr2mbit (3a), NiBr2mbis (3b), NiBr2ebit (3c), and NiBr2ebis (3d) were obtained by the reactions of Ni(PPh3)2Br2 with 2a, 2b, 2c, and 2d, respectively. However, when the corresponding ligands 2a, 2b, 2c, and 2d were treated with CoCl2 in thf solution CoII 1D coordination polymers (CoCl2mbit)n (4a), (CoCl2mbis)n (4b), (CoCl2ebit)n (4c), and (CoCl2ebis)n (4d) were obtained. All compounds were fully characterized by IR spectroscopy and elemental analysis. The crystal structures of 2c, 3a, 3b, 3c, 4a, 4b, and 4c were determined by X-ray crystallography. The local geometry around the nickel atom in complexes 3a,c was distorted tetrahedron with coordinated S(Se) and two Br atoms, and the organochalcogen ligands form an eight- or a nine-membered ring with the nickel atom included. The cobalt atom coordination polymers 4a and 4b coexist as left-handed and right-handed helical chains, but 4c formed a zigzag chain with a CH3CN solvent molecule taken up in the channel structure. After activation with methylaluminoxane (MAO), the nickel complexes exhibited high activities for addition polymerization of norbornene (1.42,×,108 g,PNBmol,1,Nih,1 for 3a). The effects of the Al/Ni ratio, reaction temperature, and reaction time to norbornene polymerization were also investigated.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


Nickel Complexes with N2O Donor Ligands: Syntheses, Structures, Catalysis and Magnetic Studies

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 32 2007
Jishnunil Chakraborty
Abstract Two new terephthalato-bridged tetranuclear polymeric NiII complexes, namely [Ni4L41(,-tp-,4 -O)(H2O)2(,-tp-,2 -O)]·2C2H5OH·CH3OH·3H2O (1) and [Ni4L42(,-tp-,4 -O)(H2O)2(,-tp-,2 -O)]·3H2O (2) [L1 = N -(3-aminopropyl)-5-bromosalicylaldimine and L2 = N -(3-aminopropyl)salicylaldimine], are reported along with the syntheses and structures of the dicyanoargentate-bridged polymeric complexes [Ni(L1)(H2O){Ag(CN)2}], (3) and [Ni(L3)(MeOH){Ag(CN)2}], (4) [L3 = N -(3-amino-2,2-dimethylpropyl)-5-bromosalicylaldimine]. All four complexes are found to be effective heterogeneous catalysts for the epoxidation of alkenes such as styrene, ,-methylstyrene and cyclohexene in the presence of tert -butyl hydroperoxide. The variable-temperature magnetic susceptibility measurements (300,2 K) of complex 1 show a fair degree of antiferromagnetic coupling between the NiII centers.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]


Tetranuclear Nickel Complexes Composed of Pairs of Dinuclear LNi2 Fragments Linked by 4,4,-Bipyrazolyl, 1,4-Bis(4,-pyrazolyl)benzene, and 4,4,-Bipyridazine: Synthesis, Structures, and Magnetic Properties

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2007
Vasile Lozan
Abstract The ability of the ligands 4,4,-bipyrazolyl (H2bpz), 1,4-bis(4,-pyrazolyl)benzene (H2bpzb), and 4,4,-bipyridazine (bpdz) to link two dioctahedral LNi2 units has been examined. Thefollowing complexes were prepared: [L1NiII2(Hbpz)][BPh4] (6[BPh4]), [L1NiII2(bpdz)][ClO4]2 (7[ClO4]2), [(L1NiII2)2(bpzb)][BPh4]2 (8[BPh4]2), and [(L2NiII2)2(bpz)][BPh4]2 (9[BPh4]2), where (L1)2, and (L2)2, represent macrocyclic hexaaza-dithiophenolate ligands. All complexes have been characterised by UV/Vis spectroscopy, IR spectroscopy, and X-ray crystallography. Whereas (Hbpz), and bpdz in 6[BPh4]2 and 7[ClO4]2 act as bidentate ligands coordinating to only one [LNi2]2+ unit, in 8[BPh4]2 and 9[BPh4]2 the (bpzb)2, and(bpz)2, units are tetradentate linkers. This is qualitatively explained in terms of the absence or presence of steric repulsions between the tBu groups of the supporting ligands and the length of the coligands. The structures of the tetranuclear complexes differ mainly in the distance between the center of the Ni···Ni axes of the isostructural [LNi2] units {14.040(1) Å in 8[BPh4]2, 9.184(1) Å in 9[BPh4]2}. The two Ni2pyrazolato planes in 9[BPh4]2 are coplanar. An analysis of the temperature-dependent magnetic susceptibility data for 9[BPh4]2 reveals the presence of weak ferromagnetic exchange interactions between the NiII ions in the binuclear [L2Ni2] subunits with values for the magnetic exchange constant J1 of 23.97 cm,1 (H = ,2JS1S2). The exchange coupling across the dipyrazolato bridge is less than 0.1 cm,1, suggesting that no significant interdimer exchange coupling occurs in 9[BPh4]2. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]


Curing Behavior of Epoxy Resin Using Controllable Curing Agents Based on Nickel Complexes

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2006
Abdollah Omrani
Abstract Summary: The curing reaction kinetics and mechanism of the diglycidyl ether of bisphenol A (DGEBA) with three complexes of Ni(II) with diethylentriamine (Dien), Pyrazole (Pz) and Pyridine (Py) as ligands have been studied using differential scanning calorimetry (DSC). The curing reaction was characterized by high cure onset and peak maximum temperatures. The kinetics of the curing reaction were evaluated using the Ozawa method. The average values of activation energy for the three nickel complexes increased in the order: Dien-based curing agent,>,Pz-based curing agent,>,Py-based curing agent. Three main curing mechanisms (catalytic, complex cation and free ligand polymerization path) have been proposed depending on the cure temperature. It was also shown that the cure kinetics of DGEBA with Dien- and Py-based complexes could be described by the Sestak-Berggren equation. The water absorption, chemical resistance and thermal stability of the thermosets were also studied. The results showed that the thermoset obtained with the Py-based complex was more thermally stable than those obtained with the other two curing agents. Activation energy versus conversion plots for the epoxy systems studied. [source]


ChemInform Abstract: Nickel Complexes of a Pincer Amidobis(amine) Ligand: Synthesis, Structure, and Activity in Stoichiometric and Catalytic C,C Bond-Forming Reactions of Alkyl Halides.

CHEMINFORM, Issue 32 2009
Oleg Vechorkin
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


ChemInform Abstract: Selective Dimerization of 1,6-Diynes Catalyzed by Ionic Liquid-Supported Nickel Complexes in an Ionic Liquid/Toluene Biphasic System.

CHEMINFORM, Issue 25 2009
Avijit Goswami
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


Two Unprecedented Inorganic,Organic Boxlike and Chainlike Hybrids Based on Arsenic,Vanadium Clusters Linked by Nickel Complexes.

CHEMINFORM, Issue 21 2007
Yanfei Qi
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]


A Stable (Amino)(phosphino)carbene as Bidentate Ligand for Palladium and Nickel Complexes: Synthesis, Structure, and Catalytic Activity.

CHEMINFORM, Issue 29 2006
Emmanuelle Teuma
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]


Highly Stereoselective Ring-Opening Addition of Terminal Acetylenes to Bicyclic Olefins Catalyzed by Nickel Complexes.

CHEMINFORM, Issue 40 2002
Dinesh Kumar Rayabarapu
No abstract is available for this article. [source]


Modular Routes Towards New N,O-Bidentate Ligands Containing an Electronically Delocalised ,-Enaminone Chelating Backbone

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2008
Udo Beckmann
Abstract Polyketones are synthesised by a transition-metal-catalysed copolymerisation of olefins and carbon monoxide. Nickel complexes with N,O-chelating ligands turned out to be promising catalysts in that field. In this work a series of new N,O ligands with an electronically delocalised ,-enaminone backbone were synthesised and fully characterised. The ligand design was inspired by the ligand found in the most efficient nickel catalyst for polyketone synthesis and developed to a highly modular LEGO® -like arsenal of reactions to versatile substituted ,-enaminone ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


Structure and conformation of a nickel complex: {2-Hydroxo-3-piperidine-1-yl-methyl-N,N,(bis-5-bromobenzylpropylenediimine)nickel(II)perchlorate}

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2004
S. M. Malathy Sony
Abstract The title compound, a nickel complex [C23H26N3O2Br2Ni.(ClO4)] (CCDC 199520) crystallizes in triclinic space group P with the cell parameters a = 10.2560(4), b = 10.8231(4), c = 12.0888(5)Å, , = 99.404(1), , = 99.780(1), , = 92.252(1)° and V = 1301.49(9)Å3. The structure was solved by Patterson method and refined by full-matrix least-squares procedures to a final R = 0.0497 using 6287 observed reflections. In the complex, the piperidine ring takes chair conformation and the geometry around the Ni ion is slightly distorted square planar. The dihedral angle between the planes [N-Ni-N and O-Ni-O] is 9.4(1)°. The chelate ring containing both the nitrogen atoms adopts twisted boat conformation. The molecules in the crystal are stabilized by N-H,O and C-H,O types of hydrogen bonds in addition to a C-H,, interaction. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Double Modification of Electrode Surface for the Selective Detection of Epinephrine and Its Application to Flow Injection Amperometric Analysis

ELECTROANALYSIS, Issue 22 2009
Guang-Ri Xu
Abstract A glassy carbon electrode having two polymer layers has been applied to selectively detect epinephrine. The inner layer formed by electropolymerization of macrocyclic nickel complex functioned as an electrocatalyst for epinephrine oxidation and the outer layer composed of hydrolyzed polyurethane ,-benzyl L -glutamate as a screening layer. Differential pulse voltammetry showed almost 100% recovery of epinephrine even in 100-fold excess of interferents. When applied to a dual glassy carbon electrode as an amperometric detector in flow injection analysis, a linear response over 0.1,,M and 10,,M was obtained. Recovery tested for 5-fold diluted human urine samples was 97.5%. [source]


Oxidation of CH3NH2 and (CH3)2NH by NiIII(cyclam)(H2O)23+ in Aqueous Solutions

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2004
Dror Shamir
Abstract NiII(1,4,8,11-tetraazacyclotetradecane)2+, NiIIL2+, is a good electrocatalyst for the oxidation of CH3NH2 and (CH3)2NH but not of (CH3)3N. The oxidation kinetics of the amines by NiIIIL(H2O)23+ indicate that the amines are good axial ligands to the tervalent nickel complex. The complexes NiIIIL[N(CH3)iH3,i](H2O)3+ are stronger oxidants than the complexes NiIIIL[N(CH3)iH3,i]23+. The oxidation is base-catalyzed and obeys a second-order rate law in NiIIILX2. It is proposed that the key step is NiIII,L(H2O)[N(CH3)iH2,i]2+ + NiIIILX2 , LNiII,N(=CH2)(CH3)i,1H2,i + NiIIL2+ + H3O+ + 2 X. Naturally, N(CH3)3 is not oxidized by this mechanism. Of special interest is the observation that the axial ligands CH3NH2 and (CH3)2NH are oxidized by the central cation, while the cyclam ligand, which has four secondary amine groups bound to the nickel(III) ion, and axially bound pendant primary amine groups, which are covalently linked to the macrocyclic ligand, are relatively stable. This difference in the behavior of axially bound amine groups is attributed to the free rotation of the axially bound N(CH3)iH3,i ligands that is required for the oxidation to proceed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]


Cyclohexene hydrogenation using Group VIII metal complexes as catalysts in heterogeneous and homogeneous conditions

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2001
E Quiroga
Abstract The stability and catalytic behaviour of a ruthenium complex with chloride and tridecylamine as ligands were studied. The hydrogenation of cyclohexene carried out in mild conditions, both in homogeneous and heterogeneous conditions, was used as a test reaction. FTIR and XPS results show that the active species is the complex itself, which is stable under the reaction conditions. XPS determination shows that the ruthenium complex is tetra-coordinated, suggesting that its formula is [RuCl2(NH2(CH2)12CH3)2]. This ruthenium complex supported on ,-Al2O3 is more active and sulfur-resistant than the same complex unsupported and even more than a nickel complex with the above mentioned ligands. The Ru complex, supported or not, is also more active and sulfur-resistant than a conventional Ru/,-Al2O3 catalyst evaluated in the same operational conditions. © 2001 Society of Chemical Industry [source]


Polymerization of ,-pinene with Schiff-base nickel complexes catalyst: Synthesis of relatively high molecular weight poly(,-pinene) at high temperature with high productivity

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2007
Peng Yu
Abstract A series of easily accessible and stable Schiff-base nickel complexes (complex 1,4) in conjunction with methylaluminoxane (MAO) were employed for the synthesis of relatively high molecular weight ,-pinene polymers at high temperature with high productivity. The ligand structure of the complex had a substantial effect on the polymerization in terms of the productivity and the molecular weight. With complex 4 in the presence of MAO, high molecular weight polymers of ,-pinene (Mn , 10,900) were obtained at 40 °C with an extremely high productivity up to 1.25 × 107 g poly,-pinene/mol of Ni. 1H NMR analyses showed that the obtained ,-pinene polymer was structurally identical to that formed by conventional cationic Lewis acid initiators. The polymerization was presumably initiated by the nickel cation formed by the reaction of the schiff-base nickel complex and MAO, while the propagation proceeded in a manner typical for a conventional carbocationic polymerization process. Direct evidence for the carbocationic polymerization was offered by the fact that quenching of the polymerization with methanol at a low monomer conversion resulted in incorporation of a methoxyl end group into the polymer chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3739,3746, 2007 [source]


Copolymerization of norbornene and styrene catalyzed by a novel anilido,imino nickel complex/methylaluminoxane system

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2006
Haiyang Gao
Abstract Copolymerizations of norbornene with styrene were carried out with a catalytic system of anilido,imino nickel complex (ArNCHC6H4NAr)NiBr (Ar = 2,6-dimethylphenyl) and methylaluminoxane in toluene. The influence of the comonomer feed content and polymerization temperature on the conversion and composition of the copolymers with (ArNCHC6H4NAr)NiBr/methylaluminoxane was investigated. An increase in the initial styrene feed content led to an increase in the incorporated styrene content of the resulting copolymer. The determination of the reactivity ratios showed a much high reactivity for norbornene (reactivity ratio for styrene = 0.26, reactivity ratio for norbornene = 20.78), which was consistent with a coordination mechanism. NMR analysis of the end groups further confirmed that the chain was initiated through a styrene secondary insertion or a norbornene insertion into NiH and terminated through ,-H elimination from an inserted styrene unit. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5237,5246, 2006 [source]


Mono- and Binuclear Arylnickel Complexes of the ,-Diimine Bridging Ligand 2,2,-Bipyrimidine (bpym)

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2010
Axel Klein
Abstract The mono- and binuclear organometallic NiII complexes [(,-bpym){Ni(Mes)Br}n] (bpym = 2,2,-bipyrimidine; n = 1 or 2; Mes = mesityl = 2,4,6-trimethylphenyl) were prepared and characterised electrochemically and spectroscopically (NMR, UV/Vis/NIR) in detail. The long-wavelength absorptions for the binuclear complex reveal a marked electronic coupling of the two metal centres over the ligand bridge via their low-lying ,*-orbitals. While the mononuclear complex undergoes rapid dissociation of the bromido ligand after one-electron reduction the binuclear derivative exhibits reversible reductive electrochemistry and both of them yield stable radical anionic complexes with mainly bpym ligand centred spin density as shown by EPR spectroscopy of the free ligand bpym and the nickel complexes. The molecular structure of the binuclear bpym complex [(,-bpym){Ni(Mes)Br}2] was studied by EXAFS in comparison to the mononuclear analogue [(bpym)Ni(Mes)Br] revealing markedly increased Ni,C/N distance of the first coordination shell for the binuclear derivative suggesting an optimum overlap for the mononuclear complex, while two nickel complex fragments {Ni(Mes)Br} are seemingly too large to fit into the bis-chelate coordination site. [source]


Nickel Complexes of N/O -Functionalized N-Heterocyclic Carbenes as Precatalysts for Michael Reactions in Air at Room Temperature Under the Much Preferred Base-Free Conditions

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2009
Sriparna Ray
Abstract A series of several new nickel precatalysts supported overN/O -functionalized N-heterocyclic carbenes (NHC) for the Michael reactions of ,-dicarbonyl, ,-keto ester, ,-diester, and ,-cyano ester compounds with ,,,-unsaturated carbonyl compounds in air at ambient temperature under the much preferred base-free conditions are reported. Specifically, the nickel complexes, [1-(R1 -aminocarbonylmethyl)-3-R2 -imidazol-2-ylidene]2Ni [R1 = 2-C6H4(OMe); R2 = Me (1b), iPr (2b), CH2Ph (3b) and R1 = 2-CH2C4H3O; R2 = Me (4b), CH2Ph (5b)] carried out the highly convenient base-free Michael addition of the activated C,H compounds across ,,,-unsaturated carbonyl compounds in air at room temperature. The complexes 1b,5b were synthesized by the direct reaction of the respective imidazolium chloride salt with NiCl2·6H2O in CH3CN in the presence of K2CO3 as a base. The exceptional stability of 1b,5b has been attributed to the deeply buried nickel,NHC ,-bonding molecular orbitals as evidenced from the density functional theory (DFT) studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


Pseudo-Octahedral Schiff Base Nickel(II) Complexes: Does Single Oxidation Always Lead to the Nickel(III) Valence Tautomer?

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 27 2008
Olaf Rotthaus
Abstract With the aim of establishing correlations between the ligand structure and the oxidation site in nickel complexes from Schiff base ligands, five ligands and their nickel complexes have been synthesized. The prototypical asymmetric Schiff base ligand HL1 contains both phenol and pyridine pendant arms with a pivotal imine nitrogen atom. Ligands HL2,5 differ from HL1 by either their phenolate para substituent, the hybridization of the pivotal nitrogen atom, and/or the N-donor properties of the pyridine moiety. The five complexes [Ni(L1,5)2] are obtained by treating the corresponding ligands with 0.5 equiv. of Ni(OAc)2·4H2O in the presence of NEt3. X-ray crystal-structure diffraction studies as well as DFT calculations reveal that [Ni(L1,5)2] involves a high-spin nickel(II) ion within a pseudo-octahedral geometry. The two ligands are arranged in a meridional fashion when the pivotal nitrogen atom is an imine {as in [Ni(L1,2)2] and [Ni(L4,5)2]}, while the fac isomer is preferred in [Ni(L3)2] (amino pivotal nitrogen atom). [Ni(L1)2] is characterized by an oxidation potential at ,0.17 V vs. Fc+/Fc. The one-electron-oxidized species [Ni(L1)2]+ exhibits an EPR signal at g = 2.21 attributed to a phenoxyl radical that is antiferromagnetically coupled to a high-spin NiII ion. [Ni(L2)2] differs from [Ni(L1)2] by the phenolate para substituent (a tert -butyl instead of the methoxyl group) and exhibits an oxidation potential that is ca. 0.16 V higher. Compared to [Ni(L1)2]+ the cation [Ni(L2)2]+ exhibits a SOMO that is more localized on the metal atom. The EPR and electrochemical signatures of [Ni(L3)2]+ are similar to those of [Ni(L1)2]+, thus showing that an imino to amino substitution compensates for a methoxy to tert -butyl one. Replacement of the pyridine by a quinoline group in [Ni(L4,5)2] makes the complexes slightly harder to oxidize. The EPR signatures of the cations [Ni(L4,5)2]+ are roughly similar to those of the pyridine analogs [Ni(L1,2)2]+. The oxidation site is thus not significantly affected by changes in the N-donor properties of the terminal imino nitrogen atom.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


Nickel Complexes and Cobalt Coordination Polymers with Organochalcogen (S, Se) Ligands Bearing an N -Methylimidazole Moiety: Syntheses, Structures, and Properties,

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2008
Wei-Guo Jia
Abstract The organochalcogen ligands (S, Se) derived from 3-methylimidazole-2-thione/selone groups mbit (2a), mbis (2b), ebit (2c), and ebis (2d) [mbit = 1,1,-methylenebis(1,3-dihydro-3-methyl-2H -imidazole-2-thione), mbis = 1,1,-methylenebis(1,3-dihydro-3-methyl-2H -imidazole-2-selone), ebit = 1,1,-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H -imidazole-2-thione), ebis = 1,1,-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H -imidazole-2-selone)] were synthesized and characterized. Mononuclear NiII complexes NiBr2mbit (3a), NiBr2mbis (3b), NiBr2ebit (3c), and NiBr2ebis (3d) were obtained by the reactions of Ni(PPh3)2Br2 with 2a, 2b, 2c, and 2d, respectively. However, when the corresponding ligands 2a, 2b, 2c, and 2d were treated with CoCl2 in thf solution CoII 1D coordination polymers (CoCl2mbit)n (4a), (CoCl2mbis)n (4b), (CoCl2ebit)n (4c), and (CoCl2ebis)n (4d) were obtained. All compounds were fully characterized by IR spectroscopy and elemental analysis. The crystal structures of 2c, 3a, 3b, 3c, 4a, 4b, and 4c were determined by X-ray crystallography. The local geometry around the nickel atom in complexes 3a,c was distorted tetrahedron with coordinated S(Se) and two Br atoms, and the organochalcogen ligands form an eight- or a nine-membered ring with the nickel atom included. The cobalt atom coordination polymers 4a and 4b coexist as left-handed and right-handed helical chains, but 4c formed a zigzag chain with a CH3CN solvent molecule taken up in the channel structure. After activation with methylaluminoxane (MAO), the nickel complexes exhibited high activities for addition polymerization of norbornene (1.42,×,108 g,PNBmol,1,Nih,1 for 3a). The effects of the Al/Ni ratio, reaction temperature, and reaction time to norbornene polymerization were also investigated.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


Studies on Nickel(II) Complexes with Amide-Based Ligands: Syntheses, Structures, Electrochemistry and Oxidation Chemistry

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2008
Jyoti Singh
Abstract The present work discusses the nickel chemistry in a set of amide-based open-chain ligands with subtle differences in the backbone or terminal amine substituents. The ligands coordinate to the Ni2+ ion through the Namide and Namine atoms maintaining a square-planar geometry. Absorption spectra and NMR studies reveal that the solid-state square-planar geometry is retained in solution. The electrochemical results suggest that the NiIII/NiII redox couple primarily depends on the N4 donors, which is composed of two Namide and twoNamine atoms and not on the peripheral substituents. All four ligands with variable backbone and substituents are equally competent in stabilizing the NiIII state. On the basis of electrochemical findings, chemical oxidations were carried out, and they reveal generation of the NiIII state in two cases, whereas decomposition was observed in others. Preliminary alkene epoxidation reactions suggest that the present nickel complexes transiently stabilize the higher oxidation state of the nickel ion that possibly participates in the oxidation of the substrates.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


Coordination Chemistry of 3-Mercapto-2-(mercaptomethyl)propanoic Acid (Dihydroasparagusic Acid) with Iron and Nickel

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2006
Phillip I. Volkers
Abstract The first transition-metal complexes bearing the natural product dihydroasparagusic acid, (HSCH2)2CHCO2H, as a ligand are reported. Various coordination modes and nuclearities are demonstrated for the chelating ligand by a series of iron and nickel complexes. Fe2[(SCH2)2CHCO2H](CO)6 retains carbonyl substitution reactivity typical of Fe2(SR)2(CO)6 complexes, yet carboxy coordination to FeI was unobserved. Coupling of the carboxylic acid with amines yields the corresponding amides Fe2[(SCH2)2CHC(O)NHR](CO)6 (R = Et, gly,O,tBu). Fe2[(SCH2)2CHCO2H](CO)4(PMe3)2 catalyzes H2 production, but no better than unfunctionalized alkyl dithiolate analogs. Reactions of the ligand with NiCl2(dppe) afforded mono-, di-, and trinuclear complexes. Noteworthy is Ni3[(SCH2)2CHCO2]2(dppe)2, which features an octahedrally coordinated NiII center linked to a pair of square-planar NiII centers. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


Cobalt and Nickel Complexes Bearing Pyrazolyliminophosphorane Ligands: Synthesis, Characterisation and Catalytic Ethylene Oligomerisation Behaviour

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2006
Cheng Zhang
Abstract Treatment of 1-(2,-azidophenyl)-3,5-dimethylpyrazole (1) with Ph2PR (R = Ph, Me) and (Ph2P)2CH2, respectively, affords the pyrazolyliminophosphoranes 2, 3 and 4. Reaction of 2 or 3 with [NiCl2(dme)] or NiBr2 yields the N,N-chelate nickel complexes 5,8, and with CoCl2 complexes 9 and 10. Reaction of 4 with [NiCl2(dme)], NiBr2 and CoCl2, respectively, affords the N,N,P-chelate complexes 11,13. Compounds 2,4 were characterised by 1H, 13C, 31P NMR and IR spectroscopy and elemental analysis, while complexes 5,13 were characterised by IR spectroscopy and elemental analysis. The structures of complexes 5, 9 and 12 were further characterised by single-crystal X-ray diffraction techniques. Complexes 5,13 are active catalysts for ethylene oligomerisation upon activation with alkylaluminium derivatives(Et2AlCl, MAO or MMAO). These complexes exhibit good to high catalytic activities (up to 3.54,×,106 g,mol,1,h,atm for the nickel complexes and 5.48,×,105 g,mol,1,h,atm for the cobalt complexes). The effects of varying ethylene pressure, temperature and aluminium co-catalyst/Ni or Co ratios with complexes 5, 9, 11 and 12 are reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


The Synthesis of the Dimethyl Ester of Quino[4,4a,5,6- efg]-Annulated 7-Demethyl-8-deethylmesoporphyrin and Three of Its Isomers with Unprecedented peri -Condensed Quinoline Porphyrin Structures.

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2004
Molecules with Outstanding Properties as Sensitizers for Photodynamic Therapy in the Far-Red Region of the Visible Spectrum
Abstract The mesoporphyrin dimethyl ester nickel complex has been formylated via the Vilsmeier method. The four possible mono meso-formyl derivatives were isolated and characterized. Wadsworth,Emmons coupling with the anion of (diethylphosphono)acetonitrile converted these aldehydes into the four novel meso acrylonitriles. Brief treatment of these acrylonitrile systems in hot trichloroacetic acid resulted in the formation of four achiral porphyrin derivatives with unprecedented nickel complexes of quino-fused porphyrins. Subsequent removal of the nickel gave four quino-porphyrin free bases: quino[4,4a,5,6- efg]-annulated 7-demethyl-8-deethylmesoporphyrin dimethyl ester 6a, 2,-(methoxycarbonyl)quino[4,4a,5,6- jkl]-annulated 12-demethyl-13-de[2,-(methoxycarbonyl)ethyl]mesoporphyrin dimethyl ester 6b, 2,-(methoxycarbonyl)quino[4,4a,5,6- qrs]-annulated 18-demethyl-17-de(2,-methoxycarbonylethyl)mesoporphyrin dimethyl ester 6c and quino[4,5,6,7- abt]-annulated 2-demethyl-3-deethylmesoporphyrin dimethyl ester 6d. The structures of these systems were unambiguously determined via mass spectroscopy and a plethora of NMR techniques. In the same way, etioporphyrin and octaethylporphyrin were converted into the corresponding peri -condensed quinoporphyrins as products, which shows that the formation of novel pericondensed quino-porphyrins is a general reaction in the porphyrin series and will have a wide scope in this field. Also, a plausible reaction mechanism for the formation of the quinoporphyrin systems was derived. As a first test for the use of these systems as sensitizers in far-red phototherapy, the quantum yield of singlet oxygen generation by 6a in toluene was studied. This quantum yield is 0.77, which is even higher than the singlet oxygen generation by sensitized meso-tetraphenylporphyrin. Secondly, when Chinese Hamster ovary (CHO) cells were incubated in medium which contained up to 15 ,g/ml of 6a, the survival rate of the cells in the dark is complete within experimental error, showing that under these conditions, 6a is not toxic to CHO cells. When CHO cells incubated in medium containing 6a in concentrations of 1 ,g/ml and higher were treated with white light of intensity 30 mW/cm2 for 15 minutes, complete cell death was observed. Based on these facts, we expect that all four achiral systems will show very promising properties to form the basis of a photodynamic therapy in far-red light. The fact that these systems are achiral is an additional bonus for medical applications. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]


Solar-thermochromism of Pseudocrystalline Nanodroplets of Ionic Liquid,NiII Complexes Immobilized inside Translucent Microporous PVDF Films

ADVANCED MATERIALS, Issue 7 2009
Xianjun Wei
Translucent composite films of poly(vinylidene fluoride), ionic liquid, and nickel complexes are successfully fabricated using thermal modulation of dissolution, casting, and drying. These films exhibit high stability in ambient storage and reversible thermochromic responses in air at temperatures achievable under sunlight, promising intelligent windows for controlling solar heat entering the built environment. [source]


Vinyl polymerization of norbornene by mono- and trinuclear nickel complexes with indanimine ligands

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2008
Guangrong Tang
Abstract A series of new indanimine ligands [ArNCC2H3(CH3)C6H2(R)OH] (Ar = Ph, R = Me (1), R = H (2), and R = Cl (3); Ar = 2,6- i -Pr2C6H3, R = Me (4), R = H (5), and R = Cl (6)) were synthesized and characterized. Reaction of indanimines with Ni(OAc)2·4H2O results in the formation of the trinuclear hexa(indaniminato)tri (nickel(II)) complexes Ni3[ArN = CC2H3(CH3)C6H2(R)O]6 (Ar = Ph, R = Me (7), R = H (8), and R = Cl (9)) and the mononuclear bis(indaniminato)nickel (II) complexes Ni[ArNCC2H3(CH3)C6H2(R)O]2 (Ar = 2,6- i -Pr2C6H3, R = Me (10), R = H (11), and R = Cl (12)). All nickel complexes were characterized by their IR, NMR spectra, and elemental analyses. In addition, X-ray structure analyses were performed for complexes 7, 10, 11, and 12. After being activated with methylaluminoxane (MAO), these nickel(II) complexes can polymerize norbornene to produce addition-type polynorbornene (PNB) with high molecular weight Mv (106 g mol,1), highly catalytic activities up to 2.18 × 107 gPNB mol,1 Ni h,1. Catalytic activities and the molecular weight of PNB have been investigated for various reaction conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 489,500, 2008 [source]


Polymerization of ,-pinene with Schiff-base nickel complexes catalyst: Synthesis of relatively high molecular weight poly(,-pinene) at high temperature with high productivity

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2007
Peng Yu
Abstract A series of easily accessible and stable Schiff-base nickel complexes (complex 1,4) in conjunction with methylaluminoxane (MAO) were employed for the synthesis of relatively high molecular weight ,-pinene polymers at high temperature with high productivity. The ligand structure of the complex had a substantial effect on the polymerization in terms of the productivity and the molecular weight. With complex 4 in the presence of MAO, high molecular weight polymers of ,-pinene (Mn , 10,900) were obtained at 40 °C with an extremely high productivity up to 1.25 × 107 g poly,-pinene/mol of Ni. 1H NMR analyses showed that the obtained ,-pinene polymer was structurally identical to that formed by conventional cationic Lewis acid initiators. The polymerization was presumably initiated by the nickel cation formed by the reaction of the schiff-base nickel complex and MAO, while the propagation proceeded in a manner typical for a conventional carbocationic polymerization process. Direct evidence for the carbocationic polymerization was offered by the fact that quenching of the polymerization with methanol at a low monomer conversion resulted in incorporation of a methoxyl end group into the polymer chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3739,3746, 2007 [source]


Curing Behavior of Epoxy Resin Using Controllable Curing Agents Based on Nickel Complexes

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2006
Abdollah Omrani
Abstract Summary: The curing reaction kinetics and mechanism of the diglycidyl ether of bisphenol A (DGEBA) with three complexes of Ni(II) with diethylentriamine (Dien), Pyrazole (Pz) and Pyridine (Py) as ligands have been studied using differential scanning calorimetry (DSC). The curing reaction was characterized by high cure onset and peak maximum temperatures. The kinetics of the curing reaction were evaluated using the Ozawa method. The average values of activation energy for the three nickel complexes increased in the order: Dien-based curing agent,>,Pz-based curing agent,>,Py-based curing agent. Three main curing mechanisms (catalytic, complex cation and free ligand polymerization path) have been proposed depending on the cure temperature. It was also shown that the cure kinetics of DGEBA with Dien- and Py-based complexes could be described by the Sestak-Berggren equation. The water absorption, chemical resistance and thermal stability of the thermosets were also studied. The results showed that the thermoset obtained with the Py-based complex was more thermally stable than those obtained with the other two curing agents. Activation energy versus conversion plots for the epoxy systems studied. [source]