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Coordination Compounds - Nomenclature of Coordination Compounds

Grade 12CBSEChemistry

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The name of the cation is written first in both positively and negatively charged coordination entities, followed by the anion.

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Ligands are named in an alphabetical order before the name of the central atom/ion. This is a change from previous rules where negative ligands preceded neutral ones.

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Names of anionic ligands end in −o-o (e.g., Cl−Cl^- becomes chlorido, CN−CN^- becomes cyanido, OH−OH^- becomes hydroxido). Neutral ligands keep their names, with exceptions like H2OH_2O (aqua), NH3NH_3 (ammine), COCO (carbonyl), and NONO (nitrosyl).

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Prefixes like mono, di, tri, etc., indicate the number of individual ligands. If the ligand name already includes a numerical prefix (e.g., ethane-1,2-diamine), then terms like bis, tris, tetrakis are used, and the ligand name is placed in parentheses.

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The oxidation state of the metal is indicated by a Roman numeral in parentheses following the name of the metal.

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If the complex ion is a cation, the metal is named same as the element. If the complex ion is an anion, the name of the metal ends with the suffix −ate-ate (e.g., FeFe becomes ferrate, AgAg becomes argentate, CuCu becomes cuprate).

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Ambidentate ligands are named either by using different names (e.g., nitro and nitrito) or by placing the symbol of the coordinating atom after the name of the ligand (e.g., SCN−SCN^- is thiocyanato-S or thiocyanato-N).

📐Formulae

Oxidation Number of Metal+∑Charges of Ligands=Net Charge of the Complex\text{Oxidation Number of Metal} + \sum \text{Charges of Ligands} = \text{Net Charge of the Complex}

[M(L)n]x  ⟹  Name: [Prefix][Ligand Name][Metal Name](Oxidation State)[M(L)_n]^x \implies \text{Name: [Prefix][Ligand Name][Metal Name](Oxidation State)}

[Co(NH3)6]Cl3→Hexaamminecobalt(III) chloride[Co(NH_3)_6]Cl_3 \rightarrow \text{Hexaamminecobalt(III) chloride}

K4[Fe(CN)6]→Potassium hexacyanidoferrate(II)K_4[Fe(CN)_6] \rightarrow \text{Potassium hexacyanidoferrate(II)}

💡Examples

Problem 1:

Write the IUPAC name for [Pt(NH3)2Cl(NH2CH3)]Cl[Pt(NH_3)_2Cl(NH_2CH_3)]Cl.

Solution:

Diamminechlorido(methylamine)platinum(II) chloride

Explanation:

Ligands are ammine (NH3NH_3), chlorido (Cl−Cl^-), and methylamine (NH2CH3NH_2CH_3). Alphabetically: ammine > chlorido > methylamine. The oxidation state of PtPt is calculated as x+2(0)+(−1)+0=+1x + 2(0) + (-1) + 0 = +1, so x=+2x = +2.

Problem 2:

Write the formula for Iron(III) hexacyanidoferrate(II).

Solution:

Fe4[Fe(CN)6]3Fe_4[Fe(CN)_6]_3

Explanation:

The cation is Fe3+Fe^{3+}. The complex anion is hexacyanidoferrate(II), which is [Fe(CN)6]4−[Fe(CN)_6]^{4-}. To balance the charges (+3 and -4), the formula becomes Fe4[Fe(CN)6]3Fe_4[Fe(CN)_6]_3.

Problem 3:

Write the IUPAC name for [Co(en)3]2(SO4)3[Co(en)_3]_2(SO_4)_3.

Solution:

Tris(ethane-1,2-diamine)cobalt(III) sulfate

Explanation:

The ligand 'en' is ethane-1,2-diamine. Since it is a polydentate ligand with a numerical prefix in its name, we use 'tris'. The oxidation state of CoCo is xx in [Co(en)3]3+[Co(en)_3]^{3+}, so x+3(0)=+3x + 3(0) = +3.

Nomenclature of Coordination Compounds Revision - Class 12 Chemistry CBSE