Question

The secondary valency of Pt in \( [Pt(en)_2Cl_2]^{2+} \) is

• A. 6
• B. 5
• C. 4
• D. 2

Hint:

Ethylenediamine (en) is a very common bidentate ligand. Always multiply its count by 2 when calculating the coordination number.

Answer 1

The Correct Option is A

Step 1: Conceptual Understanding:
In coordination chemistry, the secondary valency of a metal atom refers to its coordination number, which is the total number of ligand donor atoms that are directly bonded to the metal. This coordination number is important for understanding the structure and bonding in coordination complexes.
Step 2: Detailed Explanation:
Consider the complex \( [Pt(en)_2Cl_2]^{2+} \):
1. 'en' (ethylenediamine) is a bidentate ligand, meaning each 'en' molecule donates two pairs of electrons to the metal. Since there are 2 'en' molecules, the contribution to the coordination number is \( 2 \times 2 = 4 \).
2. 'Cl' (chloride) is a monodentate ligand, meaning each chloride ion donates one pair of electrons to the metal. There are 2 chloride ions, so the contribution to the coordination number is \( 2 \times 1 = 2 \).
The total coordination number (C.N.) is \( 4 + 2 = 6 \), which represents the secondary valency of the metal in this complex.
Step 3: Final Answer:
The secondary valency of Pt in the given complex is 6.