IUPAC NOMENCLATURE OF MONONUCLEAR
The rules are outlined below
1. In naming the entire complex, the name of the cation is given first and the anion second (just as for sodium chloride), no matter whether the cation or the anion is the complex species.
2. In the complex ion, the name of the ligand or ligands precedes that of the central metal atom (This procedure is reversed for writing formulae).
3. Ligand names generally end with 'O' if the ligand is negative ('chloro' for Cl-, 'cyano' for CN-, 'hydrido' for H-) and unmodified if the ligand is neutral ('methylamine' for MeNH2).
4. Special ligand names are 'aqua' for water, 'ammine' for ammonia, 'carbonyl' for CO, nitrosyl' for NO.
5. A Greek prefix (mono, di, tri, tetra, penta, hexa, etc.) indicates the number of each ligand (mono is usually omitted for a single ligand of a given type). If the name of the ligand itself contains the terms mono, di, tri, like triphenylphosphine, ligand name is enclosed in parentheses and its number is given with the alternate prefixes bis, tris, tetrakis instead.
For example, [Ni(PPh3)2Cl2] is named dichlorobis(triphenylphosphine) nickel(II).
6. A Roman numeral or a zero in parentheses is used to indicate the oxidation state of the central metal atom.
7. If the complex ion is negative, the name of the metal ends in 'ate' for example, ferrate, cuprate, nickelate, cobaltate etc.
8. If more than one ligand is present in the species, then the ligands are named in alphabetical order regardless of the number of each. For example, NH3 (ammine) would be considered as 'a' ligand and come before Cl-(chloro).
Some additional notes
i) Some metals in anions have special names
B Borate Au Aurate Ag Argentate Fe Ferrate
Pb Plumbate Sn Stannate Cu Cuprate Ni Nickelate
ii) Use of brackets or enclosing marks.
Square brackets are used to enclose a complex ion or neutral coordination species.
[Co(en)3]Cl3 - tris(ethylenediamine)cobalt(III) chloride
[Co(NH3)3(NO2)3] triamminetrinitrocobalt (III)
note that it is not necessary to enclose the halogens in brackets.
A systematic approach to drawing and naming coordination complexes
For the complex K3[Cr(C2O4)3].3H2O
Q1) What is the central metal ion? A1) Central metal is Chromium
Q2) What is its oxidation state? A2) O.S. is III
Q3) What is its electronic configuration? A3) electronic configuration is d3
Q4) What is its coordination number? A4) C.N. is 6(3 bidentate ligands
Q5) What is the shape of the ion? A5) structure is octahedral
Q6) Can the structure have isomers? A6) Yes, optical isomers are possible
Q7) What is the IUPAC name of the complex?
A7) Potassiumtris(oxalato) chromate(III) trihydrate
IUPAC Nomenclature of mono nuclear coordination compounds
[CoIII (NH3)5Cl]2+ pentaamminechlorocobalt(III) ion
[CoIII (NH3)6]Cl3 - Hexaamminecobalt(III) chloride
[CrIII (en)3]Cl3 - Tris (ethylenediamine)chromium(III) chloride
K4[FeII(CN)6] - Potassium hexacyanoferrate(II)
[NiII(CN)4]2- - Tetracyanonickelate(II) ion
[CuII(NH3)4]2+ - Tetraamminecopper(II) ion
[PtII Cl2(NH3)2] - Diamminedichloroplatinum(II)
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