Ammine complexes nickel

The procedures described should serve as a general guide to the preparation of nickel ammine complexes. 

Calcining a silica supported nickel ammine complex gave a nickel silicate like material with nickel ions present in an octahedral coordination surrounded by oxygens. Heating the titania supported species, however, resulted in the formation of Ni 2 d Ni cations present in small patches of nickel oxide on the... 

Complex Structure. The violet-colored solution of very stable nickel ammine complexes also confirms, through the described experiments, that practically no free nickel ions exist in the complex solution (see E9.7). The analysis of... 

In the course of a study of nickel ammine complexes, in two experiments turbidity occurred, which was interpreted as an indication of formation of Ni(OH)2. When the solubility product (log,p = -13.8, 25°C) is extrapolated to / = 0 by means of the Davies equation the following constants were obtained (log, X°g= -14.64, log, X" = 13.36) [62DAV]. These values are in line with others which refer to freshly precipitated probably amorphous Ni(OH)2, see Table V-6 [380KA], [54FEI/HAR]. 

Ni + yields a green precipitate of hydroxide Ni(OH)2 once pH > 7.2, insoluble in excess of the reagent but soluble in ammonia through the formation of blue nickel ammine complexes, in particular of hexamminenickel(II) [Ni(NH3)6] " ". Nickel hydroxide can again be separated from this solution with an excess of sodium or potassium hydroxide. 

Nickel (II) ammine Complexes. See under Ammine or Ammoniate and Coordination in Vol 1, A275ff... 

Table 8-4. Stability constant data for copper(ii) and nickel(ii) ammine complexes.

The metal hydroxides that dissolve in an excess of aqueous NH3 to form ammine complexes are derived from the twelve metals of the cobalt, nickel, copper and zinc families. Therefore, when excess NH3 is added ... 

Since the octahedral and tetrahedral configurations have the same number of unpaired electrons (that is, 2 unpaired electrons), we cannot use magnetic properties to determine whether the ammine complex of nickel(II) is Octahedral or tetrahedral. But we can determine if the complex is square planar, since the square planar complex is diamagnetic with zero unpaired electrons. 

At high initial [Fe2+] in the absence of added substrates, the stoichiometric ratio [Fe3+]oo/[L(H20)Rh00H2+]0 approaches 2.0. At lower concentrations of Fe2+, the overall reaction produces less Fe2+ because some of the newly formed L(H20)Rh02+ decomposes, presumably by loss of NH3 from the ammine complex and intramolecular ligand oxidation in the macrocyclic compounds, as observed for similar complexes of high-valent nickel, cobalt, and iron (58,118-120). Competition experiments were carried out at sufficiently high [Fe2+] to ensure that no L(H20)Rh02 + was lost in self-decay. 

Bertini et al.497 and Lever et al.495 measured the electronic spectra of a series of tetragonal nickel(II) ammine complexes and found a relationship between the Ni—N distance and the ea parameter, e decreasing when the Ni—N distance increases. 

Evidently a low ammonia concentration (0.003 Af) and a high ammonium chloride concentration (1.5 to 2 M) are favorable for efficient separation of metal ions that do not form ammine complexes (Ca" ", Mg" ). In fact, a single precipitation has been found to be effective under these conditions.To separate iron(III) from copper, zinc, and nickel, high concentrations of both ammonia and ammonium chloride produced excellent results in a single precipitation. 

The curves for calcium ions differ from those for nickel in two ways, (i) Before the end point the curves are essentially independent of pH because calcium does not form ammine complexes. (2) After the end point the pM value is smaller than for nickel because of the smaller value of the formation constant Kc y-- For the same reason, at low pH values, ay and are so small that no pM break occurs at high pH, ay approaches unity, so it is advantageous to perform calcium titrations at pH 10 to 12. 

Nickel (Ni, at. mass 58.71) usually occurs in the II oxidation state, but some complexes contain nickel in higher oxidation states (111 and IV). Nickel(II) sulphide is precipitated at pH 4. Nickel(II) hydroxide (precipitated at pH 7) dissolves in ammonia owing to formation of ammine complexes, but is insoluble in excess of NaOH. Nickel(ll) also forms stable cyanide, oxalate, and EDTA complexes. 

Procedure Gradually add, in portions, ammonia solution to the green-colored nickel chloride solution until the color turns violet. Show and compare a 3D-model for the octahedron structure of the hexa ammine complex. Slowly add sodium hydroxide solution (drop by drop) into the violet-colored solution, for comparison also to the green-colored nickel chloride solution. 

Here, the copper ion acts as a Lewis acid, and the ammonia is a Lewis base. The Cu (hydrated) ion is pale blue in solution, while the ammonia (the ammine) complex is deep blue. A similar reaction occurs with the green hydrated nickel ion to form a deep blue anunine complex. 

Bonneviot L, Clause O, Che M, Manceau A, Dexpert H (1989b) EXAFS characterization of the adsorption sites of nickel ammine and ethyldiamine complexes on a silica surface. Catalysis Today 6 39-46 Bomebusch H, Clausen BS, Steffensen G, Liitzenkirchen-Hecht D, Frahm R (1999) A new approach for QEXAFS data acquisition. J Synchrotron Rad 6 209-211 Bostick BC, Fendorf S, Barnett MO, Jardine PM, Brooks SC (2002) Uranyl surface complexes formed on subsurface media from DOE facilities. Soil Sci Soc Am J (2002) 66 99-108 Bottero JY, Manceau A, Villieras F, Tchoubar D (1994) Structure and mechanisms of formation of iron oxide hydroxide (chloride) polymers. Langmuir 10 316-319 Bourg ACM, Joss S, Schindler PW, (1979) Ternary surface complexes 2. Complex formation in the system silica-Cu(II)-2,2 bipyridyl . Chimia 33 19-21... 

When aqueous ammonia is added to aqua complexes of d block elements such as those of nickel, copper and zinc, ligand exchange takes place and a solution of the ammine complex is formed. 

Nickel(ii) Complexes.—Ammine, Amine, and Related Ligands. [Ni(NH3)g](l3)2 has been prepared by dissolving a nickel(ii) salt in aqueous ammonia and adding iodine and a five-fold excess of The reaction of hydrazine hydrate with... 

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