Question

Write IUPAC names of the following coordination compounds:
(i) [PtCl_2(en)_2]SO_4
(ii) (NH_4)_2[CoF_4]

Hint:

Remember: Anionic complexes use metal names ending in ``ate'' such as ferrate, cobaltate, cuprate and argentate.

Answer 1

Concept:
According to IUPAC nomenclature of coordination compounds:

• Name the cation first and the anion later.

• Ligands are named before the central metal atom.

• Oxidation state of the metal is written in Roman numerals.

• If the complex ion is anionic, the metal name ends with ``ate''.

• Neutral ligands such as ethylenediamine are named before anionic ligands according to alphabetical order.

Step 1: Name compound (i).
The compound is: \[ [PtCl_2(en)_2]SO_4 \] The coordination entity is: \[ [PtCl_2(en)_2]^{2+} \] because sulphate ion is: \[ SO_4^{2-} \] and the whole compound is neutral.

Step 2: Find oxidation state of platinum.
Let oxidation state of platinum be \(x\). Each chloride ligand has charge: \[ -1 \] Two chloride ligands contribute: \[ -2 \] Ethylenediamine (\(en\)) is a neutral ligand. Overall charge on complex ion: \[ +2 \] Therefore: \[ x-2=+2 \] \[ x=+4 \] Thus platinum is in oxidation state \(+4\).

Step 3: Name the ligands.
Two chloride ligands: dichlorido Two ethylenediamine ligands: bis(ethane-1,2-diamine) Since ethylenediamine is a complex ligand, the prefix ``bis'' is used.

Step 4: Write complete name.
\[ [PtCl_2(en)_2]SO_4 \] is named as: Dichloridobis(ethane-1,2-diamine)platinum(IV) sulphate.

Step 5: Name compound (ii).
The compound is: \[ (NH_4)_2[CoF_4] \] The cation is ammonium. The complex ion is: \[ [CoF_4]^{2-} \]

Step 6: Find oxidation state of cobalt.
Let oxidation state of cobalt be \(x\). Each fluoride ligand has charge: \[ -1 \] Four fluoride ligands contribute: \[ -4 \] Overall charge on complex ion: \[ -2 \] Therefore: \[ x-4=-2 \] \[ x=+2 \]

Step 7: Write complete name.
Since the complex ion is anionic, cobalt becomes cobaltate. Four fluoride ligands give: tetrafluorido Therefore: \[ (NH_4)_2[CoF_4] \] is named as: Ammonium tetrafluoridocobaltate(II). Hence: \[ (i)\;\text{Dichloridobis(ethane-1,2-diamine)platinum(IV) sulphate} \] \[ (ii)\;\text{Ammonium tetrafluoridocobaltate(II)} \]