The IUPAC name of K3[Co(C2O4)3] is:
Coordination Compounds · Class 12 · JEE Main Previous Year Question
The IUPAC name of is:
- a
Potassium tris(oxalato)cobaltate(III)
- b
Potassium tris(oxalato)cobalt(III)
- c
Potassium trioxalatocobalt(III)
- d✓
Potassium trioxalatocobaltate(III)
Potassium trioxalatocobaltate(III)
🧠 The "-ate" Trigger
When the complex ion sits inside the brackets and bears a negative charge, the metal name flips to its anionic suffix. For Co, that's "cobaltate". For Fe, "ferrate". For Cu, "cuprate". For Ni, "nickelate". This metal-name change is the single most-tested fact in IUPAC anionic-naming questions.
🗺️ Construct the Name
The compound is — three potassium cations and one anion.
Ligands. 3 × oxalato. "Oxalato" is treated as a simple ligand name in NEET/JEE convention, so we use "trioxalato", not "tris(oxalato)".
Metal & oxidation state. Bracket charge . . Anion → cobaltate(III).
Cation. Potassium (no multiplier).
Stitched: Potassium trioxalatocobaltate(III).
⚡ "Cobaltate" Wins Over "Cobalt"
If the central metal sits in an anion (square brackets carry net negative charge), the metal always takes the -ate suffix. Quick filter: any option that says "...cobalt(III)" instead of "cobaltate(III)" is wrong by definition.
⚠️ Tris(oxalato) vs Trioxalato
Some textbook variants prefer "tris(oxalato)" because oxalato itself is a substituted ligand name. JEE accepts the simpler "trioxalato" form — and that's what this question's keyed answer uses. Read the options carefully and pick the one that matches the keyed convention.
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