Nickel divalent state

Cobalt. The speciation of radiocobalt has been selected for discussion in this chapter because it exemplifies an element for which much information already exists regarding its stable chemical speciation, yet there are additional species which have become environmentally important as a result of the activities of the nuclear industry Cobalt, the middle member of the first triad of group VIII transition metals in the Periodic Table (iron, cobalt, nickel), is most stable in the divalent state when in simple compounds. Studies of radionuclide releases from nuclear power plants under tropical conditions in India seem to indicate that... 

In the divalent state nickel forms a very extensive series of compounds. This is the only oxidation state of importance in the aqueous chemistry of nickel, and, with the exception of a few special complexes of nickel in other oxidation states, Ni11 is also the only important oxidation level in its non-aqueous chemistry. 

LiNio sMnj 5O4 is an interesting derivative of LiMn204 with the nickel ions in a divalent state and the manganese ions in a tetravalent state [AMI 97, ZHO 97, HU 13b, MAN 14]. It is characterized by a high potential in the order of 4.7 V versus LiVLi at the limit of the stability window for convention electrolytes, and delivers a reversible capacity in the order of... 

Solid-state, esr spectra of [Cu(Et2dtc)] and [Cu S2P(OPr )2 2] dissolved in coordinating and noncoordinating solvents have been compared with single-crystal and powdered samples diluted with the corresponding complexes of divalent nickel and zinc. With noncoordinating... 

Reduction lowers the charge to radius ratio of transition metal ions, promoting higher rates of ligand substitution. Reduced, divalent oxidation states of manganese, iron, cobalt, and nickel are also quite soluble (Table II). 

As indicated in Figure 3.2, this is probably just the binding of hydrogen (presumably as -1- H ) to the active site at some distance from nickel. This binding induces the oxidation of the nickel center (Ni Ni ), whereby the electron initially enters the proximal Fe-S cluster. CO can bind to the divalent nickel in the Nia-S state and thereby fixes the active site in the Nia-S-CO state ... 

Cobalt and nickel are Group VlllA and copper Group IB elements. They occur predominantly in the +2 oxidation state in soils as divalent cations, though Co + may be oxidized to Co forming very insoluble compounds with Mn oxides, and... 

The high affinity shown by carboxylic acids for copper (II) compared with the remaining divalent metals of the first transition series appears to be due in part to the stabilization of the extracted complexes by the formation of the well-known dimeric structure (1) in which copper(II) carbox-ylates exist in the solid state and in non-donor solvents.54 The axial ligands, L, consist of undissociated carboxylic acid molecules55 or, in the absence of an excess amount of extractant, they may consist of water or other solvent molecules.56 Copper was successfully removed from nickel sulfate solutions on the base-metal plant at Matthey Rustenburg Refiners in South Africa by being extracted into Versatic 10 acid at a controlled pH value. The process is believed to have been discontinued only because improvements in the selective leaching of copper and nickel rendered it unnecessary. 

As is the case with Fe(III) compounds, the colors of the familiar Ni2+ solutions used as laboratory reagents are not representative of the colors of the salts themselves. The majority of anhydrous nickel salts are yellow but as with copper(II), the color may deepen markedly as the polarizability of the anion increases. Thus NiBr2 is yellow, Ni(SCN)2 brown, and Nil2 black. The green color of aqueous nickel solutions is, of course, that associated with the ion, Ni(H20) +. Although divalent nickel may, in the presence of suitable complexing agents be oxidized to the +3 and +4 or reduced to the +1 state, such reactions are rarely carried out, and the +2 state is by far the most important. 

As hinted at previously, Vogel and coworkers have recently offered an alternative interpretation of what occurs when corroles are reacted with divalent metals." This work, which has been largely focused on nickel and copper, has served to call into question the structural and metal oxidation state assignments not only of the... 

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