Tetracyanonickelate

The oxidation-number system is easily extended to include other coordination compounds. Even the interesting substances represented by the formulas Na4Ni(CN)4 and K4Pd(CN)4 create no nomenclature problem they become sodium tetracyanonickelate(0) and potassium tetracyanopaHadate(0), respectively. 

Dichlorine monoxide, which exists in very low equiUbrium concentrations in dilute HOCl solutions, is nevertheless a kineticaHy significant reactant. Eor example, although tetracyanonickelate(II) can be oxidized by chlorine in aqueous solution to /n j -Ni(III) (CN)4(H20)2 , the second-order rate constant at 25°C for oxidation with CI2O is 40 times greater than for CI2 and 2.6 x 10 greater than for HOCl (31). 

Silver halides can be dissolved in a solution of potassium tetracyanonickelate(II) in the presence of an ammonia-ammonium chloride buffer, and the nickel ion set free may be titrated with standard EDTA using murexide as indicator. 

The procedure involved in the determination of these anions is virtually that discussed in Section 10.58 for the indirect determination of silver. The anion to be determined is precipitated as the silver salt the precipitate is collected and dissolved in a solution of potassium tetracyanonickelate(II) in the presence of an ammonia/ammonium chloride buffer. Nickel ions are liberated and titrated with standard EDTA solution using murexide as indicator ... 

The method may be illustrated by the determination of bromide details for the preparation of the potassium tetracyanonickelate are given in Section 10.58. 

Pipette 25.0 mL of the bromide ion solution (0.01-0.02M) into a 400 mL beaker, add excess of dilute silver nitrate solution, filter off the precipitated silver bromide on a sintered glass filtering crucible, and wash it with cold water. Dissolve the precipitate in a warm solution prepared from 15 mL of concentrated ammonia solution, 15 mL of 1M ammonium chloride, and 0.3 g of potassium tetracyanonickelate. Dilute to 100-200 mL, add three drops of murexide indicator, and titrate with standard EDTA (0.01 M) (slowly near the end point) until the colour changes from yellow to violet. 

Silva-Avalos J, Richmond MG, Nagappan O, et al. 1990. Degradation of the metal-cyano complex tetracyanonickelate (II) by cyanide-utilizing bacterial isolates. Microbiol 56 3664-3670. 

Alkali metal salts of such tetracyanonickelate(II) anion may be crystallized from such solutions as hydrates, K2 [Ni(CN)4 3H2O upon evaporation of the solution. In strong cyanide solution, a pentacyano complex anion, red penta-cyanonickelate(ll), [Ni(CN)5] forms. Strong acids decompose cyanonickelate salts, precipitating nickel cyanide. 

D. [OCTAKIS Af, N, A "-TRIMETHYL-l,4,7-TRIAZACYCLONONANE)-CHROMIUMail) HEXAKIS TETRACYANONICKEL(II) ] BROMIDE HYDRATE, [Cr8Ni6(Me3tacn)s(CN)24]Bri2 ISHiO... 

A cyanide solution with a volume of 12.73 mL was treated with 25.00 mL of Ni2+ solution (containing excess Ni2+) to convert the cyanide into tetracyanonickelate(II) ... 

The tetracyanonickelate(II) ion is the most extensively studied square planar complex of nickel(II). TTie electronic spectrum is characterized by d-d bands at 31 000-32 000 cm-1 (eM 500-800) and charge transfer bands (eM = 6000-15 000) at 33 000-37 000 cm-1. In Figure 22 the electronic and MCD spectra of K2Ni(CN)4 are shown. In the MCD spectrum of the low energy band (d-d), since C terms are zero because the ground state is lAlg, the presence of the... 

Hydrated Ni(CN)2 dissolves in aqueous KCN and the yellow diamagnetic potassium tetracyanonickelate(II) K2Ni(CN)4 (92) crystallizes upon evaporating the solvent (equation 111). 

The compounds M(NH3)2Ni(CN)4 (M = Zn or Cd), which consist of two-dimensional polymeric sheets of tetracyanonickelate ions bridged by coordinating diamminemetal(II) cations, function as host lattices for clathration of small aromatic molecules such as thiophene, furan, pyrrole or pyridine IR studies indicate the presence of hydrogen bonding between the host lattice ammonia and the aromatic guest molecules.132,133 A crystal structure determination of the related clathrate Cd(en)Ni(CN)4(pyrrole)2 has been reported.134 Similarly, the complex Cd(py)2Ni(CN)4 consists of polymeric [Cd—Ni(CN)4] layers held together by Cd-bound pyridine.135... 

Beach, M.W. and Margerum, D.W. (1990) Kinetics of oxidation of tetracyanonickelate(II) by chlorine monoxide, chlorine, and hypochlorous acid and kinetics of chlorine monoxide formation. Inorg. Chem. 29, 1225-1232. 

The precipitate is readily soluble in excess reagent, when a yellow solution appears owing to the formation of tetracyanonickelate(II) complex ions ... 

If the solution of tetracyanonickelate(II) is heated with sodium hypobromite solution (prepared in situ by adding bromine water to sodium hydroxide solution), the complex decomposes and a black nickel(III) hydroxide precipitate is formed (difference from cobalt ions) ... 

HYDROCYANATION Diethylaluininum cyanide. Disodium tetracyanonickelate-(II). Organoaluminum cyanides. 

Disodium tetracarbonylferrate, 205-207 Disodium tetrachloropalladate, 207 Disodium tetracyanonickelate, 207 N,N -Disuccinimidyl carbonate, 208 cndo-Disulfides, 435-436... 

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