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Homework Help: Solution check for Complex Molecule IUPAC Naming

  1. May 10, 2009 #1
    1. The problem statement, all variables and given/known data
    a) Given the IUPAC name to the chemical formulas: [tex]{\left[ {Ni{{\left( {N{H_3}} \right)}_6}} \right]^{2 + }}[/tex] [tex]\left[ {CrC{l_3}{{\left( {N{H_3}} \right)}_3}} \right][/tex] [tex]{\left[ {Co{{\left( {N{O_2}} \right)}_6}} \right]^{3 - }}[/tex]

    b) Give the metal oxidation state, Coordination number and distinguish the donar atoms for each complex.

    2. The attempt at a solution
    [tex]{\left[ {Ni{{\left( {N{H_3}} \right)}_6}} \right]^{2 + }}{\rm{ - hexaaminenickate ion}}\left( {II} \right)[/tex] CN - 6, Metal oxidation state - 2+

    [tex]\left[ {CrC{l_3}{{\left( {N{H_3}} \right)}_3}} \right]{\rm{ - trisaminetriclorocromate}}\left( {III} \right)[/tex] CN - 6, Metal oxidation state - 3+

    [tex]{\left[ {Co{{\left( {N{O_2}} \right)}_6}} \right]^{3 - }}{\rm{ - hexanitrocobalt}}\left( {III} \right){\rm{ ion}}[/tex] CN - 6, Metal oxidation state 3+

    are these soluions correct?
    many thanks, pavadrin
  2. jcsd
  3. Jan 30, 2017 #2


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    Gold Member

    Well, the good news is you got the oxidation states and coordination numbers right.
    Compounds that end in -ate are anions. So the only compound that can be an -ate here is the cobalt one. Starting with the nickel compound, the proper name for a NH3 ligand is ammine, with 2 m's. So the name of [Ni(NH3)6]2+ is hexaamminenickel(II). You can add "ion" to that to make it clear that you're not talking about a neutral species.
    For the chromium species, you're almost right: triamminetrichlorochromium(III).
    For the cobalt, since the overall species is negative, you can write hexanitrocobaltate(III). Sigma also lists it as hexanitritocobaltate(III). See below.

    The reason for the two names has to do with the donor atom question. In the case of ammonia, it's pretty clear the ligand binds through the N atom. For the nitro case, there could be linkage isomerism: meaning that the NO2 group could bind through the nitrogen (in which case it's a "nitro" species), or through the oxygen (in which case it's a "nitrito" species).
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