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Question #44558

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The Question

Consider the bimetallic coordination complex with the empirical formula $\ce{FeNi(en)3F6}$ (where $\ce{en}$ = ethylenediamine). Two coordination isomers, $\mathbf{P}$ and $\mathbf{Q}$ , can be synthesized. Isomer $\mathbf{P}$ is found to be entirely diamagnetic at $298\text{ K}$ and both of its metal centers strictly obey the Effective Atomic Number (EAN) rule. Isomer $\mathbf{Q}$ is paramagnetic.

Which of the following statements is CORRECT regarding the electronic and structural features of these isomers?

Options

A.
In Isomer $\mathbf{P}$ , the oxidation states of Fe and Ni are +3 and +3 respectively, yielding an EAN of 35 for both metal centers.
B.
Isomer $\mathbf{Q}$ consists of $[\ce{Ni(en)3}]^{2+}$ and $[\ce{FeF6}]^{2-}$ where the EAN of Ni is 38 and Fe is 34, reflecting its lower kinetic stability compared to $\mathbf{P}$ .
C.
The diamagnetism of the $[\ce{NiF6}]^{2-}$ sphere in Isomer $\mathbf{P}$ proves that $\ce{F^-}$ acts as a strong-field ligand, forcing an $sp^3d^2$ hybridization.
D.
Both metal centers in Isomer $\mathbf{P}$ utilize $sp^3d^2$ hybridization because the EAN rule mandates the use of outer d-orbitals for 3d metals.

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Coordination Isomerism|EAN Rule (Sidgwick's Rule)|Valence Bond Theory Hybridization

Why This Question Is Tricky

Common Mistakes

This problem tests the intersection of Coordination Isomerism, the EAN rule, and Crystal Field Theory.

The primary trap is assuming oxidation states remain static across coordination isomers.

Students must deduce that exchanging ligands forces a shift in formal oxidation states to maintain charge balance and stability.

A secondary 'Hidden Variable' trap lies in Option C: students rigidly memorize F- as a weak-field ligand associated with sp3d2 hybridization, forgetting that a +4 oxidation state (like Ni4+) drastically increases the crystal field splitting energy (CFSE), forcing a low-spin d2sp3 configuration regardless of the ligand's position in the spectrochemical series.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Coordination Compounds - Class 12
Concept	Coordination Isomerism
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free