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2.1.6: Naming Transition Metal Complexes

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    It's useful to be able to read the name of a complex or compound and understand what that means. First, let's get straight on some vocabulary:

    COMPLEXES (metal directly bonded to ligands)

    • Complex Cation: This is a metal complex with an overall positive charge. e.g. \([CO(NH_3)_6]^{3+}\)
    • Complex Anion: This is a metal complex with an overall negative charge. e.g. \([CoCl_4(NH_3)_2]^-\)
    • Neutral Complex: This is a metal complex with zero overall charge. e.g. \([CoCl_3(NH_3)_3]\)

    COMPOUNDS (salt of one or more complexes)

    • Coordination Compounds: This is a salt where either the cation and/or the anion are metal complexes. e.g. \(K_4[Fe(CN)_6]\)

    The Rules: Naming Complexes and Coordination Compounds

    1. Naming a coordination compound (salt):
    Cation first, then anion. Also list cation first in formula.

    (just like gen chem: NaCl = sodium chloride)

    Screen Shot 2019-12-29 at 4.43.21 PM.png

    2. Naming a complex/complex ion:
    ligands first, metal second, written as one long word.

    *in the formula, the complex ion is written in
    [square brackets] and the metal is written first

    Screen Shot 2019-12-29 at 4.35.36 PM.png*if the ligand itself includes one of the prefixes, or is complicated, a second set of prefixes is used. Screen Shot 2019-12-29 at 4.36.45 PM.png

    4. Ligands are named in alphabetical order. (see example above)

    5. Anionic ligands are given “o” suffix. Neutral Ligands retain usual name. (see example above)
    Screen Shot 2019-12-29 at 4.42.29 PM.png

    6. Oxidation number of transition metals is given by (Roman Numeral).
    *for negative oxidation numbers, charge is given by (-#)

    7. Negatively charged complex ion is given suffix “-ate”.

    Screen Shot 2019-12-29 at 4.44.48 PM.png

    8. Arrangement of ligands must be specified for stereoisomers: Cis / Trans, Δ / Λ , mer / fac.

    Screen Shot 2019-12-29 at 4.46.44 PM.png

    9. Bridging Ligands between metal ions have prefix μn (n=# of atoms bridged, usually dropped if n=2).

    Screen Shot 2020-07-20 at 9.12.47 PM.png

    10. Ambidentate ligands use κ-X

    Screen Shot 2019-12-29 at 4.48.16 PM.png

    The Rules: Writing Formulas of Coordination Complexes

    The formula of a coordination complex is written in a different order than its name. The chemical symbol of the metal center is written first. The ligands are written next, with anion ligands coming before neutral ligands. If there is more than one anion or neutral ligand, they are written in alphabetical order according to the first letter in their chemical formula.

    In a coordination compound's name, when one of the ions is just an element, the number of atoms is not indicated with a prefix. Since it still has to be written in the formula, it is determined by balancing the overall charge of the compound. (For example, tetrafluorochromium(VI) chloride becomes [CrF4]Cl2.

    Exercise \(\PageIndex{1}\)

    Provide names for the following complexes:

    a) K[Cr(ox)2(OH2)2] b) [Co(NH3)5Br](NO3)2 c) [Cr(en)2Cl2]PF6 d) [Co(bpy)2(OH)Cl]ClO4

    e) [TiCl3(OH2)3] f) K3[Fe(CN)6] g) Na[Au(bpy)(CN)2]

    Answer a):

    potassium diaquabis(oxalato)chromate(III)

    Answer b):

    pentaamminebromocobalt(III) nitrate

    Answer c):

    dichlorobis(ethylenediamine)chromium(III) hexafluorophosphate

    Answer d):

    bis(bipyridine)chlorohydroxocobalt(III) perchlorate

    Answer e):


    Answer f):

    potassium hexacyanoferrate(III)

    Answer g):

    sodium bipyridinedicyanoaurate(I)

    Bipyridine is sometimes called "bipyridyl".

    Exercise \(\PageIndex{2}\)

    Draw the following structures:

    a) dicarbonylbis(1,2-dimethylphosphino)ethaneruthenium (0)

    b) potassium bipyridyltetracyanoferrate(II)

    c) pentaamminechlorochromium(III) perchlorate

    d) tetraacetonitrilecopper(I) tetrafluoroborate

    e) sodium ethylenediaminebis(oxalato)cobalt(III)

    f) chlorotris(triphenylphosphine)rhodium(I)

    Answer a):

    Screen Shot 2020-01-25 at 12.50.00 PM.png

    Answer b):

    Screen Shot 2020-01-25 at 12.50.07 PM.png

    Answer c):

    Screen Shot 2020-01-25 at 12.50.14 PM.png

    Answer d):

    Screen Shot 2020-01-25 at 12.50.21 PM.png

    Answer e):

    Screen Shot 2020-01-25 at 12.50.29 PM.png

    Answer f):

    Screen Shot 2020-01-25 at 12.50.38 PM.png


    Curated or created by Kathryn Haas

    This material is adapted from:

    This page titled 2.1.6: Naming Transition Metal Complexes is shared under a not declared license and was authored, remixed, and/or curated by Kathryn Haas.

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