Question

Write the IUPAC name of the following complex: \[ K_3[Cr(C_2O_4)_3] \]

Hint:

Negative complex → metal name ends with “-ate”. Fe → Ferrate, Cu → Cuprate, Cr → Chromate.

Answer 1

Step 1: Identify the Ligands and Metal Center.
The complex given is \( K_3[Cr(C_2O_4)_3] \), which consists of a chromium (Cr) metal center surrounded by three oxalate ligands (\( C_2O_4^{2-} \)). The oxalate ion is a bidentate ligand, meaning it bonds through two donor atoms.

Step 2: Determine the Oxidation State of the Metal.
The potassium ions (\( K^+ \)) balance the charge of the complex ion. Since three \( K^+ \) ions are present, the charge on the complex ion must be \( 3^+ \) to balance the overall charge of 0. Therefore, the oxidation state of chromium (Cr) in this complex is \( +3 \).

Step 3: Name the Ligands.
The oxalate ion (\( C_2O_4^{2-} \)) is named "oxalato" in the IUPAC nomenclature.

Step 4: Name the Complex.
- The name of the complex is based on the central metal atom (chromium), the oxidation state of the metal in parentheses, and the ligands. Since there are three oxalato ligands, we use the prefix "tris" to indicate the number of ligands.

- The full IUPAC name is: Potassium tris(oxalato)chromate(III).

Conclusion.
The IUPAC name of \( K_3[Cr(C_2O_4)_3] \) is Potassium tris(oxalato)chromate(III).