Read the IUPAC Naming Rules Before You Name a Complex
IUPAC naming is mechanical once you fix the order: ligands alphabetically (ignoring multiplying prefixes), then the metal, then its oxidation state in Roman numerals, with '-ate' added only for anionic complexes.
Chemistry questions first require the material, particles or reaction condition to be identified before a formula or rule is selected.
Ligands first, alphabetically, then the metal
For [Pt(NH3)2Cl2], 'ammine' comes before 'chlorido' alphabetically, and platinum keeps its own name (a neutral/cationic complex doesn't get the '-ate' suffix): diamminedichloridoplatinum(II) — the oxidation state is +2 here since the two Cl- balance a neutral overall complex.
Anionic complexes get the metal's Latin '-ate' name
When the whole complex ion carries a negative charge, the metal name switches to its Latinate '-ate' form: platinum becomes 'platinate', gold becomes 'aurate'. For a salt built from a cationic gold-en-aqua complex and an anionic gold-oxalato complex, the cation keeps 'gold' and the anion becomes 'aurate': diaquobis(ethylenediamine)gold(III) tris(oxalato)aurate(III).
Going from formula to name and back again
The same alphabetical-ligand, metal-then-oxidation-state logic runs in reverse when you're asked for a formula from a name. Diammine dichlorodicyano chromate(III) tells you: 2 NH3 + 2 Cl- + 2 CN- around Cr(III); since the complex carries the '-ate' suffix it must be anionic — the four anionic ligands outweigh the +3 metal charge, giving [CrCl2(CN)2(NH3)2]-.
OlympIQ exam lens
- ✓Order ligands alphabetically by name, ignoring di-/tri-/tetra- multiplying prefixes.
- ✓A negatively-charged complex ion always gets the metal's Latinate '-ate' name (platinate, aurate, ferrate).
- ✓Oxidation state in Roman numerals comes right after the metal name, derived from overall charge balance.
- ✓When a formula shows two different complex ions as cation and anion, name each independently.
Don't alphabetise by the multiplying prefix (di-, tris-) — 'dichlorido' is alphabetised under 'c', not 'd'. And the '-ate' suffix only applies when the complex ion itself is anionic, not just because an anion appears somewhere in the full salt.
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