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Transition Metal Complexes

  • Page ID
    3098
  • 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)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 CoCl42solution to form the brown Co(en)32+ complex.
    • Add a solution of dimethyl glyoxime in ethanol to another portion of the CoCl42solution to form the orange-brown Co(DMG)2 complex.
    • Add concentrated NH3 to the third portion of the CoCl42solution 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)2ions.

    Chromium

    • Dissolve a few grams of Cr(NO3)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 Cr3solution 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 Cr2O72ion is formed.
    • Add concentrated NH3 to the orange Cr2O72solution and note the change in the color of the solution as the CrO42ion is formed.

    Copper

    • Prepare a saturated solution of the Cu2ion in concentrated HCl and note the green color of the solution due to the presence of the CuCl42- ion.
    • Pour 20 mL of the CuCl42ion solution into 200 mL of water and note the formation of the light blue Cu(H2O)62+ complex.
    • Add 6 NHdrop by drop to a fresh solution of the Cu2+ ion until Cu(OH)precipitates.
    • Continue adding 6 NH3 until the solution turns the deep blue color of the Cu(NH3)42+ ion.

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