The International Union of Pure and Applied Chemistry(IUPAC) publication
Nomenclature of Inorganic Chemistry(1989), Blackwell Scientific Publishers,
contains the rules for the systematic naming of coordination compounds.
The basic rules are summarized here:
(1) Cationic part is named first followed by anionic part.
e.g K4[Fe(CN)6] 4K+ + [Fe(CN)6]4—
Here K+ is positive(cationic) part. So the name is Potassium hexacyanoferrate(II)
(2) Non-ionic or molecular complexes are given one word name.
e.g. in above complex hexacyanoferrate(II) is one word name.
(3) Naming of complexes starts from capital letter followed by small letter.
e.g. Potassium hexacyanoferrate(II) , Hexaamminecobalt(III) chloride.
(4) When writing the name of a complex, the ligands are quoted in alphabetical
order, regardless of their charges followed by central metal.
e.g. [CoCl(NH3)5]2+ Pentaamminechlorocobalt(III) ion
If the complex is represented by cation or anion, the word “ion” is written in the last.
(5) When writing the formula of complexes, the complex ion should be enclosed by square brackets. The metal is named first, then the coordinated groups are listed in the order: negative ligands, neutral ligands, positive ligands (and alphabetically according to the first symbol within each group).
(i) The names of negative ligands ends in -o, for example
F— fluoro H— hydrido HS— mercapto Cl-Chloro
OH— hydroxo S2— thio O2— oxo CN—Cyano
Br— Bromo O2
2— peroxo SO4
2—sulphato SO3
2— sulphito
NO3—nitrato
(ii) Neutral ligands have no special endings. Examples:
H2O = aqua, NH3 = ammine, O2 = dioxygen, CO= carbonyl, NO= nitrosyl
Organic ligands are usually given their common names as: phenyl, methyl, ethylenediamine, pyridine, triphenylphosphine.
(iii)Positive ligands end in -ium, examples:
NH2—NH2 hydrazinium, NO2 + nitronium
(6) Where there are several ligands of the same kind, the prefexes di-, tri- tetraare used to show the number of the ligands of that type. But the name of the ligand includes a number like -dipyridyl, ethylenediammine. In this case, bis-,
tris- , tetrakis-, pentakis- are used to avoid confusion and the name of the
ligand is enclosed in square brackets. Examples:
[Fe(C5H5)2] = Bis(cyclopentadienyl)iron(II)
(7) The oxidation state of the central metal is shown by a Roman numeral in brackets immediately following its name, example:-titanium(III)
(8) Complex positive ions and neutral molecules have no special ending but
complex negative ions end in -ate. Example:-
[CoCl(NH3)5]2+ Pentaamminechlorocobalt(III) ion
[Fe(CN)6]4— Hexacyanoferrate(II) ion
(9) If there are several ligands of different kind, they are named alphabetically
despite of the number. Examples:
K2[Cr(CN)2O2(O2)NH3] Potassium amminedicyanodioxoperoxochromate(vI)
Some Examples
Write IUPAC names of the given examples.
(i) [Ni(CO)4]0
Tetracarbonylnickel(0)
(ii) K4[Fe(CN)6] Potassium hexacyanoferrate(II)
(iii) Na[Ag(CN)2] Sodium dicyanosilver(I)
(iv) K2[HgI4 ] Potassium tetraiodomercurate(II)
(v) Na3[Al(C2O4)3] Sodium trioxalatoaluminate(III)
(vi) [Co(NH3)2(en)2]Cl3 Diamminebis(ethylenediamine)cobalt(III) chloride
(vii) K3[Fe(C2O4)3] Potassium trioxalatoferrate(III)
(viii) [Co(NH3)5SO4]Br Pentaamminesulphatocobalt(III) bromide
(ix)[Cr(H2O)6]2+ Hexaaquachromium(II) ion
(x) [Ni(CN)4]2— Tetracyanonickelate(II) ion
(xi)[Fe(H2O)6 ]SO4 Hexaaquairon(II) sulphate
(xii)[Pt(Py)4] [PtCl4] Tetrapyridine platinum(II) tetrachloroplatinate(II)
Engineering 