Nickel Derivatives Research Articles

Nickel(II) Complexes Incorporating Pyridyl, Imine and Amino Chelate Ligands: Synthesis, Structure, Isomer Preference, Structural Transformation and Reactivity Towards Nickel(III) Derivatives

AbstractFacile condensation of 2‐acetylpyridine with ethylenediamine in a 1:1 or 2:1 molar ratio yielded two neutral ligands with different denticity: 1‐amino‐4‐(2‐pyridyl)‐3‐azapent‐3‐ene (tridentate, L1) and 2,7‐bis(2‐pyridyl)‐3,6‐diazaocta‐2,6‐diene (tetradentate, L3), respectively. Replacing the ketone with 2‐pyridinecarboxaldehyde gave a similar set of condensates (L2 and L4). The tridentate mono‐Schiff bases (L1 and L2) react smoothly with Ni(ClO4)2·6H2O furnishing the brown bis‐chelate complexes (1a and 1b) with an NiN6 coordination sphere, while the tetradentate bis‐Schiff bases (L3 and L4) form green pseudo‐octahedral complexes (2a and 2b) in which NiII is present in an N4O2 coordination environment. The isomer specificity for both types of complexes is conspicuous from the representative X‐ray structures of 1a and 2a. cis‐trans‐cis and cis‐cis‐trans isomers are found exclusively for 1 and 2, respectively. The crystal structure of 2a reveals O−H···O hydrogen bond interactions assembling alternating cations and anions in an infinite chain‐like array. Cyclic voltammetric measurements of 1 and 2 in MeCN solution show a quasi‐reversible one‐electron oxidation near 0.95 and 0.87 V (vs. SCE), respectively, attributed to a NiIII‐NiII redox couple. Another irreversible NiIV‐NiIII redox response was observed at higher potential near 1.70 and 1.80 V (vs. SCE) for 1 and 2, respectively. Complexes 1 and 2 display a weak, broad d‐d transition band along with a charge‐transfer transition. Magnetic susceptibility measurements (at 298 K) confirmed that the spin states of the NiII centres in 1 and 2 are same, S = 1, in agreement with an octahedral configuration. Complexes 1 form stable reddish‐brown NiIII complexes (3) under exhaustive constant‐potential electrolysis treatment. The NiIII complexes display axial EPR spectra both at 298 K and 77 K with g⊥ > g|| indicating the presence of an unpaired electron primarily on the metal centre. Complexes of type 1 and 3 exhibit virtually superimposable cyclic voltammograms in a reverse electrode scan study which confirms no change in the coordination sphere on going from 1 to 3. The effective magnetic moment values (ca. 2.10 μB) of 3 suggest a significant orbital contribution to the paramagnetism, consistent with a tetragonally distorted low spin 3d7 system. A colour change phenomenon has been observed for type 2 complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

X-ray magnetic circular dichroism of Pseudomonas aeruginosa nickel(II) azurin.

We show that X-ray magnetic circular dichroism (XMCD) can be employed to probe the oxidation states and other electronic structural features of nickel active sites in proteins. As a calibration standard, we have measured XMCD and X-ray absorption (XAS) spectra for the nickel(II) derivative of Pseudomonas aeruginosa azurin (NiAz). Our analysis of these spectra confirms that the electronic ground state of NiAz is high-spin (S = 1); we also find that the L(3)-centroid energy is 853.1(1) eV, the branching ratio is 0.722(4), and the magnetic moment is 1.9(4) mu(B). Density functional theory (DFT) calculations on model NiAz structures establish that orbitals 3d(x2-y2) and 3d(z2) are the two valence holes in the high-spin Ni(II) ground state, and in accord with the experimentally determined orbital magnetic moment, the DFT results also demonstrate that both holes are highly delocalized, with 3d(x2-y2) having much greater ligand character.

Synthesis and characterization of meso-ferrocenylethynyl 5,15-diphenylporphyrins

A series of four meso-ferrocenylethynyl (5,15-diphenylporphyrinato)nickel(II) derivatives have been synthesized by Sonogashira coupling reactions. Three of these compounds contain the electron-withdrawing groups including –CHO, –CHC(CN) 2, and –CCC 6H 4NO 2 at the remaining meso position, with a view to preparing push–pull chromophores, in which ferrocene serves as the electron donor. All the new compounds have been characterized spectroscopically and the molecular structure of one of these porphyrins (compound 11) has also been determined. The studies show that although the ferrocenylethynyl group can extend the π system of the central porphyrin core, the cyclopentadienyl rings of ferrocene are almost orthogonal to the porphyrin ring. This hinders ferrocene serving as a good electron donor in these systems.

Temperature-induced solid-state valence tautomeric interconversion in two cobalt-Schiff base diquinone complexes.

The mixed-ligand complexes [Co(III)(tpy)(Cat-N-SQ)]Y and [Ni(II)(tpy)(Cat-N-BQ)]PF(6) (tpy = 2,2':6',2' '-terpyridine; Cat-N-BQ, Cat-N-SQ = mononegative and radical dinegative Schiff base diquinone ligand; Y = PF(6), BPh(4)) were prepared. Structural and spectroscopic data support the different charge distribution of the two compounds. The temperature-dependent electronic and spectral properties of solutions containing the [Co(III)(tpy)(Cat-N-SQ)](+) suggest that this compound undergoes a thermally driven valence tautomeric interconversion to [Co(II)(tpy)(Cat-N-BQ)](+) complex, the metal ion being in high-spin configuration. The comparison of the electrochemical properties of the cobalt and nickel derivatives supports the observed behavior. The same interconversion process was found to occur also in the solid state with a significant higher T(c) value than in solution. It was found that the previously reported [Co(III)(Cat-N-BQ)(Cat-N-SQ)] shows a similar behavior. The large difference between the interconversion T(c) in the solid state and in solution is suggested to come from the entropy changes associated with the modifications of vibronic interactions.

Syntheses, characterization and crystal structures of novel amine adducts of metal saccharinates, orotates and salicylates

Seven novel adducts of ethylenediamine (en), N, N′-dimethylethylenediamine (dmen) and N, N-dimethylethylenediamine (ndmen) with saccharinate, orotate and salicylate as counter-ions were synthesized and characterized with physico-chemical methods (IR and UV/vis spectroscopy, magnetic susceptibility and thermoanalytical measurements) and X-ray diffraction. Reaction of dmen with tetraaquabis(saccharinato- N)copper(II) dihydrate yielded diaquabis(dmen)copper(II) saccharinate, whereas with the corresponding nickel derivative it afforded bis(dmen)bis(saccharinato- O)nickel(II). In the copper complex the coordinated water and the primary nitrogen end of the donor ligand interact with the saccharinate anion [O1w⋯O3=2.833(2), N1⋯N2=2.992(2) Å]. Adjacent molecules are linked by two more hydrogen bonds into a layer structure. In the nickel compound, the dmen ligand also chelates the metal atom, which is bonded to the carbonyl oxygen of the anionic group. The negatively-charged nitrogen atom of the anion is intramolecularly linked to the dmen [N1⋯N2=2.968(2) Å]; hydrogen bonds link the molecules into layers. Under mildly basic conditions, the reaction of orotic acid with cobalt(II) afforded tetraaqua(2,6-dioxo-1,2,6-trihydropyrimidine-4-carboxylato- N, O)cobalt(II) hydrate. The complex was oxidatively reacted with en to give a mixed-ligand cobalt(III) adduct which includes both mono- and bisdeprotonated orotate ions. The metal atom in tetraaqua(2,6-dioxo-1,2,6-trihydropyrimidine-4-carboxylato- N, O)cobalt(II) hydrate is chelated by the orotato dianion through the carboxyl oxygen and 3-pyrimidyl nitrogen atoms, and its octahedral geometry is completed by four water molecules. The 1-pyrimidyl nitrogen atom engages in hydrogen bonding with the lattice water molecule. The cobalt atom is similarly chelated by the orotato dianion in bis(en)(2,6-dioxo-1,2,6-trihydropyrimidine-4-carboxylato- N, O)cobalt(III) 2,6-dioxo-1,2,3,6-tetrahydropyridimidine-4-carboxylate pentahydrate. The copper atom in the five-coordinate aqua(en)orotatocopper(II) monohydrate is chelated by the en ligand, the deprotonated N1 pyrimidine atom and the orotate carboxylate oxygen; the water molecule completes the square-pyramidal coordination. The nickel and copper atoms in bis(en)bis(salicylato- O)nickel(II) and bis(ndmen)bis(salicylato- O)copper(II) monomeric octahedral complexes are coordinated by the salicylato monoanion through the carboxylate oxygen in a monodentate fashion and by the en and ndmen molecules through the two amine nitrogen atoms in a bidentate chelating manner. In the copper complex, the carboxylate oxygen atom engages in hydrogen bonding with the lattice water molecule.

Nickel(II) and nickel(0) derivatives of bis(diphenylphosphino)amine: [N(PPh 2) 2] 2Ni, (Ph 3P) 2Ni[(Ph 2P) 2NH]. Synthesis, characterization, and some properties

Disproportionation of nickel(I) bis(triphenylphosphino)bis(trimethylsilyl)amide, (Ph 3P) 2NiN(SiMe 3) 2, in the presence of bis(diphenylphosphino)amine, (Ph 2P) 2NH, yields Ni(II) and Ni(0) phosphinoamide complexes: [N(Ph 2P) 2] 2Ni ( 1), (Ph 3P) 2Ni[(Ph 2P) 2NH] ( 2). Ether solution, containing 2 and Ph 3P (1:2) reacts with dioxygen (one equivalent) to form triphenylphosphinoxide adduct (Ph 3P) 2Ni[(Ph 2P) 2NH⋯OPPh 3] ( 3) in high yield. The crystal structures of compounds 1 and 3 have been determined by X-ray diffraction method.

Adamantane-like cluster complexes of mixed-valent copper-copper and nickel-copper thiolates.

Square-planar copper(II) and nickel(II) derivatives of the cis-dithiolate N(2)S(2) ligand bis(N,N'-2-mercapto-2-methylpropyl)-1,5-diazocyclooctane, (bme*daco)M, nucleate four Cu(I)Cl moieties, forming M(II)(2)Cu(I)(4)S(4) clusters with unusual triply bridging thiolates, mu(3)-SR, in the topological form of adamantane. As determined by X-ray crystallography, the (bme*daco)M (M = Cu or Ni) metallothiolate serves as a bidentate ligand that bridges four Cu(I) ions, utilizing all lone pairs on sulfurs. Further characterization by electrochemical and electronic spectral measurements suggests greater electron delocalization in the all-copper complex as compared to the NiCu heterometallic complex. Mass spectral data imply that the mixed-metal Ni(II)(2)Cu(I)(4)S(4) is more stable toward CuCl loss than Cu(II)(2)Cu(I)(4)S(4), a result that is corroborated by extraction of Cu(I) by 1,2-bis(diphenylphosphino)ethane in the latter but not the former.

Hexacyanometalate molecular chemistry: di-, tri-, tetra-, hexa- and heptanuclear heterobimetallic complexes; control of nuclearity and structural anisotropy.

Following a bottom-up approach to nanomaterials, we present a rational synthetic route to high-spin and anisotropic molecules based on hexacyanometalate [M(CN)(6)](3-) cores. Part 1 of this series was devoted to isotropic heptanuclear clusters; herein, we discuss the nuclearity and the structural anisotropy of nickel(II) derivatives. By changing either the stoichiometry, the nature of the terminal ligand, or the counterion, it is possible to tune the nuclearity of the polynuclear compounds and therefore to control the structural anisotropy. We present the synthesis and the characterisation by mass spectrometry, X-ray crystallography and magnetic susceptibility of bi-, tri-, tetra-, hexa- and heptanuclear species [M(CN)(n)(CN-M'L)(6-n)](m+) (with n=0-5; M=Cr(III), Co(III), M'=Ni(II); L=pentadentate ligand). Thus, with M=Cr(III), d(3), S=3/2, a dinuclear complex [Cr(III)(CN)(5)(CN-NiL(n))](9+), (L(n)=polydentate ligand) was built and characterised, showing a spin ground state, S(G)=5/2, with a ferromagnetic interaction J(Cr,Cu)=+18.5 cm(-1). With M=Co(III) (d(6), S=0) were built di-, tri-, tetra-, hexa and hepanuclear CoNi species: CoNi, CoNi(2), CoNi(3), CoNi(5) and CoNi(6). By a first approximation, they behave as one, two, three, five and six isolated nickel(II) complexes, respectively, but more accurate studies allow us to evaluate the weak antiferromagnetic coupling constant between two next-nearest neighbours M'-Co-M'.

3-Fluoropyridyl nickel complexes as useful tools for the selective synthesis of new 2,4,5,6-tetrafluoropyridines: a route complementing the established methods to access fluorinated pyridines

Treatment of [Ni(COD)2] with 3-chlorotetrafluoropyridine in the presence of PEt3 or PCy3 effects the formation of the complexes trans-[NiCl(3-C5NF4)(PEt3)2] (1) and trans-[NiCl(3-C5NF4)(PCy3)2] (2), respectively. Reaction of 1 with MeLi gives trans-[NiMe(3-C5NF4)(PEt3)2] (3). Treatment of 3 with air yields 3-methyltetrafluoropyridine. The reaction of 1 with CO affords 1-(2,4,5,6-tetrafluoropyridin-3-yl)ethanone (6), which slowly converts into 1-(2,5,6-trifluoropyridin-3-yl)ethanone (7) in the presence of PEt3. The structure of the complexes 1 and 3 have been determined by X-ray crystallography. The Ni–C distances to the pyridyl ligand are 1.894(1) and 1.936(2) Å, respectively. The Ni–C bond length to the methyl group in 3 is 1.991(3) Å. The studies reported in this paper demonstrate the synthesis of nickel derivatives of tetrafluoropyridine with the metal in the 3-position as well as the preparation of otherwise not accessible 3-substituted tetrafluoropyridines by C–C coupling reactions.

Alkane Oxygenation with Hydrogen Peroxide Catalysed by Soluble Derivatives of Nickel and Platinum

Various alkanes can be oxidised by hydrogen peroxide in acetonitrile solution at 70°C if Ni(ClO4)2 (in the presence of 1,4,7-trimethyl-1,4,7-triazacyclononane) or H2PtCl6 are used as catalysts; whereas the nickel-catalysed reaction seems to proceed via attack of hydroxyl radicals on an alkane, the oxidation in the presence of platinum occurs possibly with participation of oxo or peroxo derivatives of this metal.

Vibrational characteristics of new double tungstates Li2MII(WO4)2 (M = Co, Ni and Cu)

AbstractFor the first time, Raman and IR studies were performed on new double tungstates Li2MII(WO4)2 (M = Co, Ni and Cu) crystallizing in the wolframite‐type structure. The observed vibrational modes were assigned to the respective motions of atoms in the unit cell. The vibrational properties of the Cu derivative differ significantly from those of the cobalt and nickel derivatives. The differences were attributed to the differences in the crystal structures. A comparison of the results with literature data for MIIWO4 and LiMIII(WO4)2 (MII = Zn, Fe, Cu; MIII = Fe, In, Sc), crystallizing in the wolframite‐like structure, revealed a very large splitting for a few bridging modes and large shifts of the low‐wavenumber modes towards higher wavenumbers in the case of Li2MII(WO4)2. These features were assigned to different arrangements of tungsten–oxygen interactions within the infinite chains, which results in the formation of two non‐equivalent oxygen bridges in the structure of the compounds studied. Copyright © 2002 John Wiley & Sons, Ltd.

Synthesis and characterisation of ring-coupled cyclopentadienyl and indenyl bimetallic derivatives of nickel

The reaction of NiCl 2(PPh 3) 2 with 0.5 equivalents of the salts Li 2[CMe 2(C 5H 4) 2] ( 1), Li 2[CMe 2(C 9H 6) 2] ( 2) or Li 2[(C 5H 4)CMe 2(C 9H 6)] ( 3) is an efficient route to the synthesis of ring-coupled cyclopentadienyl and indenyl homobimetallic nickel derivatives. The new binuclear complexes [Cl(PPh 3)Ni{μ-(η-C 5H 4)CMe 2(η-C 5H 4)}Ni(PPh 3)Cl] ( 4), [(PPh 3) 2Ni{μ-(η-C 5H 4)CMe 2(η-C 5H 4)}Ni(PPh 3) 2][PF 6] 2 ( 5), [(PPh 3) 2Ni{μ-(η-C 9H 6)CMe 2(η-C 9H 6)}Ni(PPh 3) 2][PF 6] 2 ( 6), [Cl(PPh 3)Ni{μ-(η-C 5H 4)CMe 2(η-C 9H 6)}Ni(PPh 3)Cl] ( 7), [(PPh 3) 2Ni{μ-(η-C 5H 4)CMe 2(η-C 9H 6)}Ni(PPh 3)Cl][PF 6] ( 8), [(PPh 3) 2Ni{μ-(η-C 5H 4)CMe 2(η-C 9H 6)}Ni(PPh 3) 2][PF 6] 2 ( 9) have been prepared and characterised. The X-ray crystal structure of 5 is reported.

Complexation of nickel(II) and lead(II) cations with the tripodal nitrilo-tris(methylenephenylphosphinic) acid (H 3L). X-ray crystal structure of the dimer [Ni(HL)(DMSO)] 2·2DMSO

A series of dimeric complexes have been isolated by the reaction of M(CH 3COO) 2· xH 2O (M II=Ni, Pb) with nitrilo-tris(methylenephenylphosphinic) acid (H 3L) in dimethylsulfoxide or pyridine or water. A complete single crystal structure determination has been carried out on the nickel derivative, which displays a dimeric structure [Ni(HL)(DMSO)] 2·2DMSO. All the compounds have been characterized through magnetic measurements, thermogravimetric and calorimetric analyses.

A structural and theoretical analysis of transition metalloporphodimethenes and their relationship with metalloporphyrins.

The paper reports the synthesis of the first-row transition metal hexaethylporphodimethene derivatives [(Et6N4)M] [M=Mn, 3; M=Co, 5; M = Cu, 7] on a multigram scale, which makes them easily available for reactivity studies. After synthesis they were converted into the corresponding five-coordinate [(Et6,N4)M(L)] [M = Mn, L =THF, 8; M =Co, L = Py, 9] and six-coordinate [(Et6,N4)M(L)2] [M = Mn, L = THF, 10; M = Mn, L = Py, 11] derivatives. The compounds mentioned above and those recently reported, namely the iron and nickel derivatives 4, 6, 12, and 13, permit the presentation of the first coherent report on the structural, optical, magnetic, and electronic characteristics of the first-row transition metal porphodimethene derivatives. The experimental results, coupled with a detailed theoretical analysis (Density Functional Theory, DFT), give the appropriate background for future development of the porphodimethene skeleton, which paves the way from porphyrinogen to porphyrins. In addition, this report, encompassing the entire first row of transition metal ion porphodimethenes, allows a valuable comparison to be made with the corresponding metallated porphyrins, thus establishing the peculiar differences in terms of structural and electronic properties and potential reactivity.

1H and 13CNMR studies of 1,4,8,11,15,18-hexadecyl-22,25-bis(6-hydroxyhexyl)phthalocyanine and its nickel derivative

1,4,8,11,15,18-Hexadecyl-22,25-bis(6-hydroxyhexyl)phthalocyanine and its nickel derivative have been studied by 1 H and 13 C NMR in deuterochloroform solution at ambient probe temperature. The assignments of the proton atoms and carbon atoms in the studied phthalocyanines have been confirmed by 2D COSY NMR and 2D heteronuclear COSY NMR respectively.

Unit cell determination of 2,3,9,10,16,17,23,24- octapentoxyphthalocyanine and its nickel derivative using electron and X-ray powder diffraction

2,3,9,10,16,17,23,24-Octapentoxyphthalocyanine and its nickel derivative have been studied by means of electron and X-ray powder diffraction. The results reveal that the metal-free compound forms monoclinic crystals (space group C2/c) with unit cell constants a = 4.202 nm , b = 0.4977 nm , c = 3.345 nm , β = 98.9 ° and Z = 4 molecules per unit cell. 2,3,9,10,16,17,23,24-Octapentoxyphthalocyaninatonickel(II) is likely to be isomorphous to its metal-free analogue, but occurs in a second phase which is also stable at room temperature. This is identified to be a crystalline primitive hexagonal phase with cell constants a = b = 2.50 nm and c = 0.33 nm . It is assumed that the molecules form a columnar structure along the c-axis, whereas the hexagonal cross-section in the ab-plane goes back to the molecular disc shape. Imaging of monoclinic crystals of 2,3,9,10,16,17,23,24-octapentoxyphthalocyanine in an energy-filtering transmission electron microscope (EFTEM) can be performed to resolve 2 nm structures only, owing to specimen damage. According to the diffraction pattern, the micrograph provides a view along [001] and shows directly that the structure can be described in terms of parallel columnar stacks of molecules along the b-axis, the distance between neighbouring stacks being [Formula: see text]. The results show that the structures of both the metal-free compound and its nickel analogue are dominated by π–π interactions between the macrocycles, which is a marked difference from the structures of 1,4,8,11,15,18,22,25-octasubstituted phthalocyanines.

Chemistry of nickel tetrafluoropyridyl derivatives: their versatile behaviour with Brønsted acids and the Lewis acid BF3 †

Treatment of trans-[NiF(2-C5NF4)(PEt3)2] (C5NF4 = tetrafluoropyridyl) (1) with HCl effects the formation of the air stable chloride complex trans-[NiCl(2-C5NF4)(PEt3)2] (2). The reaction of 2 with excess HCl slowly yields 2,3,4,5-tetrafluoropyridine (4). On reaction of 4 with [Ni(COD)(PEt3)2], the C–F activation product trans-[NiF(2-C5NF3H)(PEt3)2] (5) is formed instantly. The bifluoride compound trans-[Ni(FHF)(2-C5NF4)(PEt3)2] (6) is obtained on treatment of 1 with Et3N·3HF. Reaction of 2 with HBF4 yields the binuclear complex [NiCl{μ-κ2(C,N)-(2-C5NF4)}(PEt3)]2 (7). The X-ray crystal structure of 7 reveals a “butterfly”-shaped dimeric complex with square-planar coordination at both nickel atoms, with Ni–N distances of 1.965(4) and 1.955(4) A and Ni–C distances of 1.884(5) and 1.875(5) A. Treatment of 1 with BF3·OEt2 in the presence of acetonitrile yields the cationic compound trans-[Ni(2-C5NF4)(NCMe)(PEt3)2]BF4 (8), while reaction of trans-[Ni(OTf)(2-C5NF4)(PEt3)2] (3) with NaBAr′4 and acetonitrile gives trans-[Ni(2-C5NF4)(NCMe)(PEt3)2]BAr′4 (9) [Ar′ = 3,5-C6H3(CF3)2]. The studies reported in this paper provide methods for the synthesis of tetrafluoropyridines substituted in the 2-position and demonstrate the behaviour of nickel derivatives with Bronsted acids and the Lewis acid BF3.

A Convenient Synthetic Route to Polyether-Tagged Cyclam Ligands andTheir Nickel Derivatives

A Convenient Synthetic Route to Polyether-Tagged Cyclam Ligands andTheir Nickel Derivatives

A Convenient Synthetic Route to Polyether-Tagged Cyclam Ligands andTheir Nickel Derivatives

A Convenient Synthetic Route to Polyether-Tagged Cyclam Ligands andTheir Nickel Derivatives

A Convenient Synthetic Route to Polyether-Tagged Cyclam Ligands andTheir Nickel Derivatives

A specific strategy is described for the synthesis of stable polyethylene oxide tagged tetraazamacrocycles (PEO-cyclam) in five steps (overall yields for 12 and 13 48% and 22%, respectively). Various attempts via classical pathways demonstrated: (i) the low reactivity of PEO derivatives, and (ii) the necessity of a stabiliser arm between the cyclam and the PEO chain. Nickel complexes have been prepared and characterised by electrochemistry.