Chemistry Q75 – JEE-MAIN 2025

Home Chemistry Coordination CompoundsQuestion #348

A metal complex with a formula

M C l_{4} \cdot 3 N H_{3}

is involved in

s p^{3} d^{2}

hybridisation. It upon reaction with excess of

A g N O_{3}

solution gives '

x

' moles of

A g C l

. Consider '

x

' is equal to the number of lone pairs of electron present in central atom of

B r F_{5}

. Then the number of geometrical isomers exhibited by the complex is _______.

Enter Calculated Numerical Value:

Clue 1 of 3: VSEPR Theory and Coordination Number

First, determine the number of lone pairs on the central atom of $B r F_{5}$ using VSEPR theory. Then, use the given hybridization to determine the coordination number of the metal complex.

🧠 Full Solution Path

Step 1: Determine 'x' and the coordination number of the complex✦ Active

For $B r F_{5}$ : Bromine (Br) is the central atom with 7 valence electrons. It forms 5 single bonds with 5 Fluorine (F) atoms, using 5 electrons. The remaining electrons are $7 - 5 = 2$ , which form 1 lone pair. Thus, $x = 1$ .

The complex has $s p^{3} d^{2}$ hybridisation, which corresponds to an octahedral geometry. An octahedral complex has a coordination number of 6.

Step 2: Determine the formula of the coordination complex○ Expand

The complex $M C l_{4} \cdot 3 N H_{3}$ reacts with excess $A g N O_{3}$ to give $x = 1$ mole of $A g C l$ . This indicates that 1 chloride ion is outside the coordination sphere and can be precipitated.

Since the coordination number is 6, the complex must contain $3 N H_{3}$ ligands and 3 $C l$ ligands within the coordination sphere. Therefore, the formula of the complex is $[M (N H_{3})_{3} C l_{3}] C l$ . The coordination entity is $[M (N H_{3})_{3} C l_{3}]$ .

Step 3: Determine the number of geometrical isomers○ Expand

The coordination entity $[M (N H_{3})_{3} C l_{3}]$ is an octahedral complex of the type $M A_{3} B_{3}$ , where $A = N H_{3}$ and $B = C l$ .

Complexes of the type $M A_{3} B_{3}$ exhibit two geometrical isomers: facial (fac) and meridional (mer).

Therefore, the number of geometrical isomers exhibited by the complex is 2.

💡 Teacher's Secret Hint

Remember the specific arrangements for fac and mer isomers in $M A_{3} B_{3}$ complexes.

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Chemistry Question 75 – JEE-MAIN 2025

Clue 1 of 3: VSEPR Theory and Coordination Number

🧠 Full Solution Path