IUPAC Nomenclature: Formula → Name

CHENomenclature & Numbers

Given a formula, you name the complex by stating ligands alphabetically before the metal, with the metal's oxidation state in Roman numerals in parentheses. Anionic complexes take the suffix -ate, and getting ligand names, prefixes and ordering right is the whole battle.

Order: name ligands first (alphabetically by ligand name), then the central metal; cation is named before anion as in any salt.
Anionic ligands end in -o: $Cl^-$ chlorido, $CN^-$ cyanido, $OH^-$ hydroxido, $C_2O_4^{2-}$ oxalato, $SO_4^{2-}$ sulfato; neutral ligands keep their name except $H_2O$ = aqua, $NH_3$ = ammine, CO = carbonyl, NO = nitrosyl.
Number of ligands: di, tri, tetra for simple ligands; bis, tris, tetrakis for ligands that already contain a prefix or are complex (e.g. ethane-1,2-diamine $\rightarrow$ bis(ethane-1,2-diamine)).
If the complex ion is an anion, the metal name takes the suffix -ate, often built on the Latin stem: ferrate (Fe), cuprate (Cu), argentate (Ag), aurate (Au), stannate (Sn), plumbate (Pb); a few use the English stem, e.g. zincate (Zn) and nickelate (Ni).
Oxidation state of the metal is written as a Roman numeral in parentheses right after the metal name, with no space: e.g. cobalt(III), iron(II).
Worked patterns: $[Co(NH_3)_6]Cl_3$ = hexaamminecobalt(III) chloride; $K_4[Fe(CN)_6]$ = potassium hexacyanidoferrate(II); $[Ni(CO)_4]$ = tetracarbonylnickel(0); $Na_2[Zn(OH)_4]$ = sodium tetrahydroxidozincate(II).
Alphabetise by the ligand name ignoring the multiplying prefix: in $[CoCl_2(NH_3)_4]Cl$ , ammine (a) precedes chlorido (c) $\rightarrow$ tetraamminedichloridocobalt(III) chloride.
The name is written as one continuous word with no spaces inside the complex; the only space is between the cation name and the anion name (as in any salt).
Ambidentate-ligand names specify the donor atom: $NO_2^-$ bound through N = nitrito-N (older: nitro), through O = nitrito-O (older: nitrito); $SCN^-$ = thiocyanato-S, and bound through N = isothiocyanato (thiocyanato-N).
For bridging ligands (rarely needed at ISC) the prefix $\mu$ is used, e.g. $\mu$ -hydroxido linking two metals; ordinary terminal ligands need no such prefix.
Write the oxidation number, not the ionic charge of the complex: name from the metal's oxidation state. The overall ion charge is implied by the counter-ions, not stated in the name.

Where the marks go

Alphabetising by the multiplying prefix instead of the ligand name (e.g. ordering by 'tetra-' or 'di-') — ignore di/tri/tetra and bis/tris when alphabetising.
Forgetting the -ate suffix (and the Latin stem) for anionic complexes: it is ferrate, cuprate, plumbate — not 'ironate', 'copperate', 'leadate'.
Putting the metal's overall ion charge in parentheses instead of its oxidation number — the Roman numeral is the oxidation state.
Using the old name 'chloro' for $Cl^-$ : current IUPAC uses chlorido (the -ido ending applies to anionic ligands).
Inserting a space inside the complex name or before the parenthesised oxidation state — the complex name is one unbroken word, e.g. 'cobalt(III)' not 'cobalt (III)'.

How the board asks it

Structure / namingalphabetical ligand order, -ate suffix and oxidation-state roman numeral
Write the IUPAC name of each of the following coordination compounds: (i) $[Co(NH_3)_4Cl_2]Cl$ (ii) $K_4[Fe(CN)_6]$ (iii) $[Ni(CO)_4]$ .
Structure / namingbuilding the complex ion from ligands, charges and counter-ions
Write the formula of each of the following coordination compounds: (i) potassium tetrahydroxidozincate(II) (ii) sodium hexafluoridoaluminate(III).
Structure / namingcharge balance in the complex ion fixing the roman numeral
In the complex $Na_2[Zn(OH)_4]$ , calculate the oxidation state of zinc and hence write the IUPAC name of the compound.
Give reasonslatin versus english stems for anionic complexes
Account for the fact that the anionic complex of copper is named cuprate and not 'copperate', whereas that of zinc is named zincate.
Structure / namingdonor-atom specification for ambidentate ligands
Give the IUPAC name used when the $NO_2^-$ ligand is bound to the metal through nitrogen and the name used when it is bound through oxygen, giving one example of each.

Practise this topic

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Written for Sublevo. Question text quoted anywhere in these notes is the Council’s and carries its year and paper; the board’s own diagrams are not reproduced.