IUPAC NOMENCLATURE OF COORDINATION COMPOUNDS

 IUPAC NOMENCLATURE OF COORDINATION COMPOUNDS-The present system of nomenclature recommended by the Inorganic Nomenclature Committee of the I.U.P.A.C.

The main rules of naming of complexes are -

 I). If a coordination compound is ionic, the name of cation is given first whether or not it is the complex ion followed by the name of the anion just like naming a simple salt. The names of cation and anion are separated by a space.

       Ex.

                   K₄ [Fe (CN)₆]

 the naming of this complex starts with potassium.

(II) Within a complex ion/coordination entity, the ligands are named first followed by the metal ion.

i.e., ligands are named in alphabetical order before the name of the central     atom/ion

         The ligands be be neutral, anionic or cationic.

Names of the ligands

(i)            The neutral ligands are named as the molecule

ligand	IUPAC name	ligand	IUPAC name
C5H5N	(pyridine)	CO	carbonyl
(C6H5)3P	Triphenyl phosphine	NO	nitrosyl
H2N CH2CH2NH2	ethylene diamine	H2O	Aqua
		NH3 ammonia	ammine

 

                       

    (ii)(a) Anionic ligands ending with 'ide' are named by replacing the 'ide' with  suffix 'O' or  replacing ~e by -O.

           Example

anion	Symbol	IUPAC name
Chloride	Cl-	Chlorido
Bromide	Br-	Bromido
Nitride	N3–	Nitrido
Cyanide	CN-	Cyano/ Cyanido
Amide	NH2–	Amido
Imide	NH2–	Imido
Phosphide	P3-	Phosphido
Sulphide	S2–	Sulphido
Oxide	O2-	Oxo
Hydroxide	OH–	Hydroxo
(b)Ligands whose names end in 'ite' or 'ate' by replacing the ending 'e' with 'o' as follows.
anion	symbol	IUPAC name of ligand
Carbonate	CO32–	Carbonato
Sulphite	SO32–	Sulphito
Oxalate	C2O42–	Oxalato (Ox)2–
Acetate	CH3COO—	Acetato
Sulphate	SO42–	Sulphato
Nitrite	ONO — (bonded through oxygen)	Nitrito-O-
	NO2 — (bonded through nitrogen)	Nitrito-N- [ or Nitro]
Thiosulphate	S2O3 –2	Thiosulphato

                          (EDTA^4-)- ethylenediaminetetraacetate

                          (EDTA^3-)- ethylenediaminetriacetate

    iii).Positive ligands naming ends in 'ium'

NH₂—NH₃ ⁺ (Hydrazinium),

NO₂ ⁺ (nitronium);

NO⁺ (nitrosonium)

(III) If ligands are present more than once, then their repetation is indicated by prefixes   like di, tri, tetra etc. However, when the name of the ligand includes a number. 

Ex. - dipyridyl, ethylene diamine, then bis, tris, tetrakis are used in place of di, tri, tetra,             etc.

 Example-

                    [Pt(NH₃)₆]Cl₄      Hexaamineplatinum(IV) chloride

                       [Cu(en)₂] S0₄   Bis (ethane-l,2-diamine) copper(II) sulphate

(IV)Order of naming ligands: When more than one type of ligands are present, they are   named in alphabetical order without separation by hyphen.

 Example-

                       [Co(NH₃)₄H₂OC1]Cl  Tetraaquamineaquochloridocobait(llI) chloride

                       [Cr(H₂0)₄Cl₂]⁺            Tetraaquodichloridochromium(III) ion

(V)The oxidation state of the central metal is shown by Roman numeral in small bracket     (parenthesis) followed by its name. Ex-

               [Cr(H20)₄Cl₂]⁺  Tetraaquodichloridochromium(III) ion

(VI) Complex positive ions and neutral coordination compounds have no special ending but complex negative ions always end in the suffix -ate. In most of the cases, the  suffix -ate is fixed to English names of the metals but in some cases -ate is fixed with Latin names of metals.  

Example-

        K₃[Fe (CN)₅NO]     

 Potassium pentacyanonitrosylferrate(II)