Color, solubility, and complex ion equilibria of nickel(II) species in aqueous solution

Abstract

Reagents are added in a specified order to a large beaker containing an aqueous solution of nickel sulfate. Complex ions of nickel (II) are prepared by using aqueous solutions of ammonia, ethylenediamine, dimethylglyoxime, and cyanide ion.As each complex ion is formed its color and solubility are observed. Two alternate procedures may be used. MaterialsProcedure A 1000-ml beaker magnetic stirrer with stirring bar 300 ml distilled water 20 ml lMNiS04 40 ml 5M NH3 20 ml 25% ethylenediamine 25 ml 1% dimethylglyoxime 200 ml 1 M KCN Alternate Procedure B 7 600-ml beakers 6 glass stirring rods 2100 ml distilled water 140 ml 1 M NiS04 40 ml 5 M NH3 30 ml 25% ethylenediamine 25 ml 1% dimethylglyoxime 80 ml 1 M KCN Alternate Procedure C 2-1 beaker, preferably with approximate graduations 4 1-1 beakers, preferably with approximate graduations 4 glass stirring rods

Inorganic chemistry laboratory experiment on an energetic nickel (II) coordination compound, aimed at third-year undergraduate students

“…With the ligand ethylenediamine C 2 H 4 (NH 2 ) 2 , tris(ethylenediamine)nickel (II) [Ni((NH 2 ) 2 C 2 H 4 ) 3 ] 2+ forms. These complexes differ in color (green, blue and purple respectively) due to differences in energy between the degenerate t 2g -e g orbitals which is in line with the differences in the Lewis basicity of the ligands (Roberts & Field, 1950;Shakhashiri, Dirreen, & Juergens, 1980;Summerlin, Borgford, & Ealy, 1987). Hydrazine N 2 H 4 is another ligand of Ni 2+ , leading to tris(hydrazine)nickel(II) [Ni(N 2 H 4 ) 3 ] 2+ .…”

Reactivity of nickel

“…Such a procedure is particularly useful for classroom demonstrations, especially to show the relative driving forces present in the various reactions. Some nickel one-pot reactions involving ammonia, ethylenediamine, dimethylglyoxime, and cyanide complex ions have been published elsewhere (10,11). The procedure described here is suitable for demonstration in small classrooms, If done individually by students, the procedure could readily be scaled down; if used in a large classroom, a larger scale could be used.…”

Crystal Field Splitting Energy (Δo) and Racah Parameters (B) of Some Metal-Saccharine and Metal-Saccharine-Ethylenediamine Complexes

“…In crystal field theory, the only role of the ligands in transition metal complexes has been to produce the splitting of the d-orbitals. The bonding between the metal and the surrounding ligand molecules was presumed to be purely ionic in nature [1][2] . The crystal field theory modified to admit that there is some covalent bonding in addition to electrostatic interaction between the metal ion and its ligands is known as the ligand field theory.…”