Question

What is the co-ordination number of metal in [Fe(C$_2$O$_4$)$_3$]$^{3-}$?

• A. Two
• B. Three
• C. Six
• D. Four

Answer 1

The Correct Option is C

The coordination number of a metal ion in a complex refers to the number of ligand donor atoms bonded to the metal. In the complex [Fe(C₂O₄)₃]^3-, the ligand is oxalate (C₂O₄^2-), which is a bidentate ligand. This means each oxalate ligand can form two bonds with the metal ion.

Let's calculate: 

1. The complex contains three oxalate ligands: [Fe(C₂O₄)₃]^3-.
2. Each oxalate ligand coordinates with two donor sites.
3. Therefore, the total number of coordination sites is 3 ligands × 2 donor sites per ligand = 6.

Thus, the coordination number of the metal (Fe) in the complex is six.

Answer 2

The coordination number of iron (Fe) in the complex ion [Fe(C₂O₄)₃] ^3- is six. This is because each oxalate ion (C₂O₄^2-) is bidentate, meaning it can form two bonds with the central metal ion, iron (Fe). In this case, there are three oxalate ions, each attaching to the iron through two donor atoms, resulting in a total of six bonds, which gives the iron a coordination number of six.

The bidentate nature of the oxalate ion allows for the formation of a stable chelate, where the metal ion is surrounded by the donor atoms from the ligand, increasing the stability of the complex.