Transition Metal Complexes
- Page ID
- 222047
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Chemical Concept Demonstrated
- Transition metal chemistry
Demonstrations
Nickel
- Dissolve 1-1.5 g NiCl2 in 40 mL concentrated HCL to form the yellow-green NiCl64- complex ion.
- Decant NiCl64- into 500 mL water to produce the blue-green Ni(H2O)62+ complex ion. Divide this solution into two portions: 350 mL and 175 mL.
- Add 1.5 g solid EDTA and about 45 mL 2 M NaOAc to the smaller portion of the Ni(H2O)62+ complex to form the blue Ni(EDTA) complex.
- Add 30 mL concentrated NH3 to the larger portion of the Ni(H2O)62+ complex to form the blue Ni(NH3)62+complex ion. Divide this solution into two equal portions.
- Add a dilute aqueous solution of ethylene diamine to one portion of the Ni(NH3)62+ complex to form a lavender complex for which the formula Ni(en)(NH3)42+ has been proposed.
- Add a solution of dimethyl glyoxime in ethanol to the other portion of the Ni(NH3)62+ complex to form the red Ni(DMG)2 complex.
Cobalt
- Dissolve several grams of CoCl2 in concentrated HCl to form the deep-blue CoCl42- complex ion. Pour some of this solution into water to form the pink Co(H2O)62+ complex. Divide this solution into three equal portions.
- Add a dilute aqueous solution of ethylene diamine to one portion of the CoCl42- solution to form the brown Co(en)32+ complex.
- Add a solution of dimethyl glyoxime in ethanol to another portion of the CoCl42- solution to form the orange-brown Co(DMG)2 complex.
- Add concentrated NH3 to the third portion of the CoCl42- solution to form the blue Co(NH3)62+ complex.
Iron
- Add an aqueous solution of KSCN drop by drop to an aqueous solution of the Fe3+ ion to form a mixture of the Fe(SCN)2+ and Fe(SCN)2+ ions.
Chromium
- Dissolve a few grams of Cr(NO3)3 in 45 mL concentrated HCl and decant the resulting solution into 200 mL of water. Divide the solution into two portions.
- Add a dilute aqueous solution of ethylene diamine to one portion of the Cr3+ solution to form the lavender Cr(en)33+ complex.
- Add concentrated NH3 to the other portion of the Cr3+ solution to form a green solution of the Cr(NH3)63+complex.
- Add a few drops of concentrated HCl to a yellow solution of the CrO42- ion and note the change in the color of the solution to orange as the Cr2O72- ion is formed.
- Add concentrated NH3 to the orange Cr2O72- solution and note the change in the color of the solution as the CrO42- ion is formed.
Copper
- Prepare a saturated solution of the Cu2+ ion in concentrated HCl and note the green color of the solution due to the presence of the CuCl42- ion.
- Pour 20 mL of the CuCl42- ion solution into 200 mL of water and note the formation of the light blue Cu(H2O)62+ complex.
- Add 6 M NH3 drop by drop to a fresh solution of the Cu2+ ion until Cu(OH)2 precipitates.
- Continue adding 6 M NH3 until the solution turns the deep blue color of the Cu(NH3)42+ ion.
Contributors
- Dr. George Bodner (Purdue University)