Question

Write IUPAC names of the following coordination compounds:
(i) [PtCl₂(en)₂](NO₃)₂
(ii) [Cr(NH₃)₆][Co(CN)₆]

Hint:

Balance charges from the counter ions to get the metal oxidation number, use bis(ethane-1,2-diamine) for en, and end the anionic metal in -ate.

Answer 1

We name each compound by first fixing the metal oxidation state from the overall charge balance, then listing ligands alphabetically.
Compound (i) [PtCl₂(en)₂](NO₃)₂:
Step 1: Two NO₃^- counter ions mean the complex ion bears a +2 charge.
Step 2: Chloride contributes -1 each and en is neutral, so Pt must be +4 to leave a net +2. Platinum is therefore platinum(IV).
Step 3: Because en already contains the prefix di- inside its name, we use bis(ethane-1,2-diamine); chlorido comes first alphabetically. Full name: dichloridobis(ethane-1,2-diamine)platinum(IV) nitrate.
Compound (ii) [Cr(NH₃)₆][Co(CN)₆]:
Step 1: Both ammine and cyanido counts are six. For neutrality the cationic Cr complex is +3 and the anionic Co complex is -3.
Step 2: Chromium is chromium(III); cobalt sits in an anionic sphere so it becomes cobaltate(III). Writing cation then anion: hexaamminechromium(III) hexacyanidocobaltate(III).