Question

What is the coordination number of Cobalt in $[Co(en)_3]^{3+}$?

• A. 3
• B. 4
• C. 6
• D. 2

Hint:

Bidentate ligands like \(en\) contribute two bonds each. Multiply number of ligands by their denticity to find coordination number.

Answer 1

The Correct Option is C

Topic - Coordination Compounds (Ligands and Coordination Number):
The coordination number is determined by the total number of sigma bonds formed between the ligands and the central metal atom.
Step 1: Understanding the Question:
The goal is to find the coordination number of Cobalt in the complex ion \([Co(en)_3]^{3+}\).
Step 2: Key Formula or Approach:
Coordination Number (C.N.) = (Number of ligands) \(\times\) (Denticity of the ligand).
\(en\) stands for ethylenediamine, which is a bidentate ligand.
Step 3: Detailed Solution:
1. Identify the ligand: \(en\) (ethylenediamine) is \(H_2N-CH_2-CH_2-NH_2\).
2. Determine denticity: Since it has two donor nitrogen atoms, its denticity is 2.
3. Calculate C.N.: There are 3 such ligands.
\[ \text{C.N.} = 3 \times 2 = 6 \] This means there are 6 coordinate bonds formed with the Cobalt ion.
Step 4: Final Answer:
The coordination number is 6.