Question

What is the coordination number of Fe in the complex \([Fe(C_2O_4)_3]^{3-}\)?

• A. 3
• B. 4
• C. 6
• D. 9

Hint:

Coordination number = number of donor atoms attached to the central metal atom. For bidentate ligands, multiply the number of ligands by \(2\).

Answer 1

The Correct Option is C

Concept: The coordination number of a metal ion in a complex is the number of donor atoms directly bonded to the central metal atom. A ligand may be:
• Monodentate (one donor atom)
• Bidentate (two donor atoms)

Step 1: Identify the ligand type. Oxalate ion \((C_2O_4^{2-})\) is a bidentate ligand.

Step 2: Count the ligands in the complex. \[ [Fe(C_2O_4)_3]^{3-} \] There are three oxalate ligands.

Step 3: Calculate the coordination number. Each oxalate ligand provides two donor atoms. \[ 3 \times 2 = 6 \] Thus, the coordination number of Fe is \(6\).