Nickel complexes equilibrium constants

Spiro TG, Ballhausen CJ (1961) Complexes of l,3-diamino-2-aminomethylpropane with nickel(II). Equilibrium constants and visible spectra. Acta Chem Scand 15 1707... 

An equilibrium constant for binding of 3.8c to the nickel(II)(L-tryptophan) complex of 805 M has been obtained, compared to 530 M in the presence of glycine... 

Note that for the nickel complex, the equilibrium constant corresponds to less than one free Ni2 ion per liter of solution of 0.01 M Ni2 in I M NaCN. The other complexes are even more stable. 

Equilibrium Constants and Thermodynamic Parameters for the Blue-Yellow Interconversion of Nickel(II) Complexes... 

When styrene is added to HNi[P(0-o-tolyl)3]3CN, the solution goes from yellow to red and the hydride is quantitatively converted to alkyl complex. However, addition of excess styrene to HNiL3CN—B(p-tolyl)3 causes a color to change to orange and leaves most of the nickel as hydride complex, as shown by both IR and NMR spectroscopy. Thus, the Lewis acid decreases the equilibrium constant for reaction (26) relative to reaction (25). 

Tolman has shown that the equilibrium constants for the reactions of 38 substituted ethylenes with Ni[P(0-o-tolyls)]3 in benzene, to form (ENE)bis-(tri-o-tolylphosphite)nickel complexes, is sensitive to the ethylene s structure, eqn. (2) (ref. 7). Values of Ki at 25° vary from 10 for cyclohexene to... 

The equilibrium constant for the monomer trimer reaction of bis[(2,6-dimethyl-heptane-3,5-dione)nickel(ii), in benzene at 30°C, is 2 x 10312 mol 2. Adduct formation with pyridine to form Ni2L4py and NiL2py2 was also examined.518 The reactions between Lewis bases and the square-planar bis-(2,2,6,6-tetramethylheptane-3,5-dione)nickel(n) to form complexes were examined in solution and equilibrium constants and enthalpies determined.519... 

Adduct formation between nitrogen bases (py, substituted py, o-phen) and bis(mono-thio- 3-diketonato)nickel(ii) (137) in solution has been examined and equilibrium constants were determined. Electronic spectra point to a planar four-co-ordinate structure for the (137) complexes and a six-co-ordinate one for the adducts.585... 

Progressive addition of Eu(fod)3 to the nickel complex in CDCI3 showed shifts depicted in Fig. 10.25. It is clear that 1 1 adduct is formed with an adduct formation constant of K 103 M-1 as estimated from the equilibrium... 

Although a statistical factor contributes to the equilibrium constants for many types of reactions, it is in reactions of the type being considered here—the replacement of one neutral ligand by another neutral ligand— that this factor may be the principal factor in causing variation of Kn with n. Other series of reactions of this type are the formation of ammonia complexes in aqueous solution. The variation of Kn with n observed for the chromium (III)/water-methyl alcohol system is slightly smaller than observed for ammonia complexes of cobalt(II) (18) and nickel(II) (19) ... 

Bis(alkylxanthato)nickel(ii) complexes [19] are highly suited for NMR study. Proton shifts and equilibrium constants for the equilibrium ... 

Tolman has shown that the equilibrium constants for the reactions of 38 substituted alkenes with Ni[P(0-o-tolyl)3]3 (13) in benzene, to form (ENE)bis(tri-o-tolylphosphite)nickel complexes (14), are sensitive to the structure of the alkene (equation 13). Values of K[ at 25 °C vary from 10 to 4 x 10. The stability of the complex is enhanced by electron-withdrawing substituents such as cyano and car-boxy and lowered by alkyl groups. That resonance involving unshared electrons on the oxygen of an al-koxy group overpowers the inductive effect is indicated by the relative values of Ki for allyl methyl ether, 1-hexene and vinyl butyl ether which diminish in that order by factors of 3 1 0.006. 

The polarographic determination of manganese, iron, cobalt and nickel is not so often used as that of the above mentioned elements. Probably, competition with other analytical methods is the main reason. However, the polarography of these metals has been thoroughly investigated and it is frequently used for studies of equilibrium constants of their complexes. 

The kinetics of butadiene polymerized by bis(7T-allyl nickel trifluoro-acetate) has been studied by Teyssie et al. [173]. Equilibrium constants for the formation of the complex (with aromatic compounds which give the equibinary polymer), calculated from cryoscopic measurements or polymer micro-structure, are 6—7 and 26—35 respectively for benzene and nitrobenzene. The higher concentration of active centres compared with... 

Nickel is extracted from alkaline ammonia solutions by LIX 64N, but its equilibrium constant is five orders of magnitude smaller than that of copper.8 Also, it forms ammonia complexes more extensively than copper, which enhances the selectivity of LIX 64N for copper over nickel. Under conditions of simultaneous extraction the parameters of the chemical-reaction model for each individual metal are able to predict the iwo-metal equilibria provided that the equilibrium distribution of species in the aqueous phase is taken into account. 

Amine-extraction equilibria can also be modeled by chemical-reaction equilibrium constants. Figure 8.3-3 indicates that cations such as iron(IIl), zinc, cobelt(ll) and coppeifU) exhibit high distribution coefficients with chloride solutions, wherese nickel. iron(II), and manganese are not extracted to any great extent. The besis for the differences in distribution coefficients lies mainly in the tendency for the former group of cations to fonn chloride complexes. Stability constants for these complexes are available in the literature,11 and they can be used to develop quantitative phase-equilibrium models. 

Nickel, tris( 1,10-phenanthroline)-racemization, 24,466 solid state, 467 structure, 64 Nickel(I) complexes magnetic properties, 274 Nickel(II) complexes, 470 allogonism, 207 equilibrium constants solvent effect, 516 isomerism, 184 liquid-liquid extraction, 544 magnetic properties, 274 5-mcrcaptoamine alkydation, 417 photoreactivity, 407... 

The relative stabilities of the thioether complexes vary depending on both the metal and the other ligands present. Cobalt, nickel and copper in their -h 2 oxidation state form more stable complexes with thioethers than with ether ligands, whereas Zn shows the opposite behavior. For RSCH2CO2H the equilibrium constants decrease in the order Ag > Cu > Cd Co > Mn a Zn > Ni . For the ligand S(CH2C02H)2 a similar series has been found, with Ni (more typical) between Cu and Co". ... 

Analogous investigations were performed by Madeja et al. [Ma 76] with the mixed complex consisting of the hydrogen-bond containing nickel(II) macrocyclic complex (I) and thiocyanate ion. The equilibrium constants determined in solutions prepared with various donor solvents are listed in Table 4.8. By comparison with Table 4.7, it can be seen that, with the exception of acetonitrile, the stability of the thiocyanate complex is higher than that of the iodide complex in every solvent this... 

Hill and Irving [Hi 69] used calorimetric measurements and Rao and Mathur [Ra 71] studied the temperature dependence of the equilibrium constants both groups found that the heat of the protonation of acetylacetone was higher in water-dioxane mixtures than in water. The heats of formation of the copper and nickel complexes, determined by the latter workers, reflect a similar tendency. 

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