Question

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

Hint:

Important naming rules for coordination compounds:

• Negative complex ions use metal names ending in ``-ate''.

• Oxalate ligand is named as ``oxalato''.

• For complex ligand names, use prefixes such as: bis, tris, tetrakis instead of di, tri, tetra

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

Answer 1

Concept: The IUPAC nomenclature of coordination compounds follows a systematic set of rules. To name a coordination compound correctly, we must identify:

• The cation and anion.

• The ligand(s) present.

• The oxidation state of the central metal atom.

• Whether the complex ion is cationic, anionic or neutral.
The naming of ligands is done before naming the central metal atom, and the oxidation state of the metal is written in Roman numerals within parentheses.

Step 1: Identifying the cation and complex ion. The given compound is \[ K_3[Cr(C_2O_4)_3] \] The cation present is \[ 3K^+ \] and the complex ion is \[ [Cr(C_2O_4)_3]^{3-} \] Since three potassium ions are required to neutralize the charge on the complex ion, the charge on the complex ion is \[ -3 \]

Step 2: Identifying the ligand. The ligand present is \[ C_2O_4^{2-} \] which is known as the \[ \boxed{\text{Oxalato}} \] ligand. Since there are three oxalato ligands attached to chromium, the prefix used is \[ \boxed{\text{tris}} \] The prefix ``tris'' is used instead of ``tri'' because the ligand name itself contains more than one syllable. Thus, the ligand portion of the name becomes \[ \boxed{\text{tris(oxalato)}} \]

Step 3: Calculating the oxidation state of chromium. Let the oxidation state of chromium be \(x\). Each oxalato ligand carries a charge of \[ -2 \] Since there are three oxalato ligands, \[ \text{Total ligand charge} = 3(-2) = -6 \] The charge on the complex ion is \[ -3 \] Therefore, \[ x-6=-3 \] \[ x=+3 \] Hence, the oxidation state of chromium is \[ \boxed{+3} \]

Step 4: Naming the metal atom. Since the complex ion carries a negative charge, the metal name ends with the suffix ``-ate''. Therefore, \[ \text{Chromium} \rightarrow \text{Chromate} \] The oxidation state is written as \[ (III) \] Thus, the metal part of the name becomes \[ \boxed{\text{chromate(III)}} \]

Step 5: Writing the complete IUPAC name. The cation is named first: Potassium followed by the name of the complex ion: tris(oxalato)chromate(III) Hence, the complete IUPAC name is \[ \boxed{\text{Potassium tris(oxalato)chromate(III)}} \]

Final Answer: \[ \boxed{\text{Potassium tris(oxalato)chromate(III)}} \]