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The redox chemistry of the heterobimetallic triple‐decker complexes [(Cp*Fe)(Cp′′′Co)(μ,η5:η4‐E5)] (E=P (1), As (2), Cp*=1,2,3,4,5‐pentamethyl‐cyclopentadienyl, Cp′′′=1,2,4‐tri‐tertbutyl‐cyclopentadienyl) and [(Cp′′′Co)(Cp′′′Ni)(μ,η3:η3‐E3)] (E=P (10), As (11)) was investigated. Compound 1 and 2 could be oxidized to the monocations 3 and 4 and further to the dications 5 and 6, while the initially folded cyclo‐E5 ligand planarizes upon oxidation. The reduction leads to an opposite change in the geometry of the middle deck, which is now folded stronger into the direction of the other metal fragment (formation of monoanions 7 and 8). For the arsenic compound 8, a different behavior is found since a fragmentation into an As6 (9) and As3 ligand complex occurs. The Co and Ni triple‐decker complexes 10 and 11 can be oxidized initially to the heterometallic monocations 12 and 13, which are not stable in solution and convert selectively into the homometallic nickel complexes 14 and 15 and the cobalt complexes 16 and 17. This behavior was further proven by the oxidation of [(Cp′′′Co)(Cp′′Ni)(μ,η3:η2‐P3)] (19, Cp′′=1,3‐di‐tertbutyl‐cyclopentadienyl) comprising two different Cp ligands. The transfer of {CpRM} fragments can be suppressed when a {W(CO)5} unit is coordinated to the P3 ligand (20) prior to the oxidation and the mixed cobalt and nickel cation 21 can be isolated. The reduction of 10 and 11 yields the heterometallic monoanions 22 and 23, where no transfer of the {CpRM} fragments is observed., The redox chemistry of heterobimetallic triple‐decker complexes (Fe/Co and Co/Ni) with polypnictogen ligands (E=P, As) was studied first by cyclic voltammetry and then experimentally. The complexes respond to the addition and withdrawal of electrons either by the rearrangement of the triple‐decker geometry, by the fragmentation of the En ligand and/or by the exchange of {Cp′′′M} fragments.

A new polyniobotungstate, Cs11K7[(Ge4W36Nb12O156)Ni(H2O)2]·29H2O (1) based on {GeW9Nb3O40} fundamental building units, was successfully obtained. Photocatalytic study has shown that 1 has efficient photocatalytic water splitting activity.

Sorption of nickel cations on natural sorbent silica clay was studied. The sorption isotherms were constructed and the quantitative characteristics of the process of sorption on a sorbent were determined.

International audience; The location of the divalent nickel cation exchanged in low amount in dehydrated NaX is identified by a combination of experimental (XAS) and theoretical (DFT) approaches. The Ni-O and Ni-T distances as well as the coordination numbers evaluated from experiments are in good agreement with the predicted models obtained from calculations. After dehydration, the migration of Ni2+ towards the hexagonal prism is confirmed and three distinct possible nickel sites are predicted. The results show the tendency of Ni2+ to get closer to the most basic framework oxygen atoms

A thermodynamic interpretation of the ligand field stabilization energy appropriate to pseudo-octahedral d 8 complexes is employed to estimate the synergistic enhancement of the glass transition temperature in blends of nickel acetate with poly(4-vinylpyridine) (P4VP). The maximum enhancement of T g is ≃100 o C, which occurs at a metal/polymer-repeat-unit concentration of approximately 1:2 on a molar basis. This suggests that the nickel cation coordinates to two pyridine ligands under favorable conditions

The complex of (TMA)2[Ni(H2O)6][β-Mo8O26] (I) has been synthesized via hydrothermal reaction under 130 °C. The crystal structure was determined by single crystal X-ray diffraction at room temperature. Crystal data: M=1498.62, Monoclinic, space group C2/c (No.15), a=15.9812(13) A, b=13.5690(11) A, c=16.7782(13) A, α=90°, β=96.760(2)°, γ=90°, and Z=4. It is composed of an inorganic cluster [β-Mo8O26]4−, six-hydrated bivalent nickel cation, and two organic amines TMA+.

The title compound, [Ni(chedam)(H2O)3]·1.5H2O [H2chedam = 4-hydroxy­pyridine-2,6-dicarboxylic acid, C7H5NO5], consists of one nickel cation, one chedam ligand, three coordinated water mol­ecules and 1.5 uncoordinated water mol­ecules. The nickel(II) cation is six-coordinate, with a distorted octa­hedral geometry.

In the title compound, [Ni(NCS)2(CH3CN)2]n, the NiII cation is coordinated by two N-bonded and two S-bonded thio­cyanate anions, as well as two acetonitrile mol­ecules in an octa­hedral NiN4S2 coordination mode. The asymmetric unit comprises one nickel cation, two thio­cyanate anions and two actonitrile mol­ecules. In the crystal, the NiII cations are connected by bridging thio­cyanate anions into a three-dimensional coordination network.

The title compound, [Ni(C2H2N3)Cl]n, has been prepared by the hydro­thermal reaction of nickel(II) chloride and 1,2,4-triazole. The nickel cation is coordinated in a slightly distorted tetra­hedral environment, by one Cl atom and three N atoms from different triazolate ligands. The polymeric layer is formed by the triply bridging nature of the 1,2,4-triazolate bonded to three different Ni atoms through its three N atoms. The layer contains both binuclear units and tetra­nuclear cavities. In the binuclear unit, two Ni atoms are bridged by two nearly coplanar triazolate groups through the 1,2-positions, affording a six-membered ring around an inversion center. Each binuclear unit is further connected to four parallel units through the 4-positions of the triazolate groups. Four adjacent units, which are parallel in pairs, afford 16-membered tetra­nuclear cavities. In such a cavity, the two nearest-neighbor Ni atoms are bridged by a single triazolate group through the 1,4-positions.

The purpose of this paper is to study the anodic passivity of the nickel in sulphuric and hydrofluoric acids. Theoretical expressions for the current and the impedance are established and compared with experimental data. We conclude, that, in anodic range, the electrode surface is always covered by an intermediate of reaction where the nickel cation is partial or full oxided.

Reversible potentials (E R) have been measured for nickel hydroxide/oxyhydroxide couples over a range of KOH concentrations from 0·01–10 M. It is shown that the couples derived from the parentα- andβ-Ni(OH)2 systems can be distinguished by the relative change in KOH level on oxidation and reduction. In the case of couples derived from theα-class of materials a dependence of 0·470 moles of KOH per 2e change is found compared with 0·102 moles of KOH per 2e change for theβ-class of materials. Couples derived from theα- andβ-Ni(OH)2 systems can be encountered in a series of ‘activated’ and ‘de-activated’ forms having a range of formal potentialsE 0 ′ . ‘Activated’. and ‘de-activated’β-Ni(OH)2/β-NiOOH couples are found to lie in the range 0·443–0·470 V whilstα-Ni(OH)2/γ-NiOOH couples lie in the range 0·392–0·440 V w.r.t. Hg/HgO/KOH. It is demonstrated for ‘de-activated’,β-Ni(OH)2/β-NiOOH couples thatE R is independent of the degree of oxidation of the nickel cation between states of charge of 25% and 70%. SimilarlyE R is constant for states of charge between 12% and 60% for ‘activated’α-Ni(OH)2/γ-NiOOH couples. The constant potential regions are considered to be derived from heterogeneous equilibria between pairs of co-existing phases both containing nickel in upper and lower states of oxidation. Differences inE 0 ′ between the ‘activated’ and ‘de-activated’ couples are considered to be related to the degree of order/disorder in the crystal lattice.

Komplexe Methylnickelverbindungen werden durch kationische Methylierung von L4Ni (L = (CH3)3P) dargestellt. Die oxidative Addition von Methyljodid an L4Ni, die in weniger polaren Losungsmitteln zu L3NiJ2 fuhrt, bleibt in Acetonitril auf der Stufe des Methyltetrakis(trimethylphosphin)nickel-Kations stehen. Methylnickelkomplexe entstehen auch bei der Reaktion von L4Ni mit Acetylverbindungen. Dabei decarbonyliert ein Teil des L4Ni die primar gebildete Acetylnickelverbindung. Aus der Reaktion von L3Ni(CO) mit Acetylchlorid kann komplexes Acetylnickelchlorid erhalten werden. Fur die bekannten Ni°-Komplexe L4Ni, L3Ni(CO) und L2Ni(CO)2 (L = (CH3)3P) werden einfache, ergiebige Synthesen angegeben. Stable Methylnickel Compounds, VI: Syntheses via Cationic Methylation Methylnickel complexes are synthesized via cationic methylation of L4Ni(L =(CH3)3P). Oxidative addition of methyl iodide to L4 Ni, which leads to L3NiI2in less polar solvents, affords only the methyltetrakis(trimethylphosphine)nickel cation as a first product in acetonitrile. Methylnickel complexes are also obtained by the reaction of L4Ni with acetyl compounds whereby part of the L4Ni decarbonylates the acetylnickel complexes initially formed. From the reaction of L3Ni(CO) with acetyl chloride acetylnickel compounds can be obtained. Convenient high yield syntheses for the complexes L4Ni, L3Ni(CO), and L2Ni(Co)2 (L = (CH3)3P) are described.

The equilibrium between the nickel cation and phosphite anion was studied on the basis of potentiometric pH measurement in aqueous solution. The procedure selected to study the equilibria was subjected to statistical analysis, from which the experimental and calculatory conditions of its applicability were concluded. The association constant for the particle NiH2PO3+ was found to be K1 = 28 ± 6, for the particle NiHPO3 this is K2 = (3·6 ± 2·6) 103.

International audience; Peat moss, a natural inexpensive material, is able to play an important rrle in treatment processes of metal-bearing industrial effluents since it adsorbs, complexes or exchanges various metal cations. This paper presents kinetics and thermodynamics of batch metal removal reactions by 50 g/l (dry wt) eutrophic or oligotrophic peat particles using Cu 2+, Cd 2÷, Zn 2÷ and Ni 2÷ concentrations ranging from 0.01 to 100 mM. Metal cation removal reactions are moderately rapid in l0 mM metal unbuffered solutions: the forward kinetic constant ranges between 0.005 and 0.17 M-1 s-1, and equilibrium is reached within about 1 h. Under these conditions of pH (2.2-4.2) and concentrations, apparent binding equilibrium constants were found to range between 2 and 3150 M-1 depending upon the peat origin and the metal cation. In 0-6.5 pH-buffered metal cation solutions, the four cations binding reactions behaved differently demonstrating that metal binding equilibrium constant decrease in the order Ni 2+ > Cu 2+ > Cd 2+ = Zn 2÷. When pH is higher than 6.7, more than 90% of a 10 mM metal cation solution is removed by 50 g/l peat particles and metal binding capacities equal 200 mmol kg-1 dry wt, whatever the metal nature and the peat origin. Except for nickel cation which is very strongly bound to peat, all metal cations are completely released when pH is fixed below 1.5.