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Question #44599

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The Question

A neutral transition metal complex $\mathbf{X}$ has the empirical formula \ce{Ru(CO)4Cl2}. It strictly obeys the 18-electron rule. $\mathbf{X}$ exists as two geometric isomers, $\mathbf{P}$ and $\mathbf{Q}$ . Isomer $\mathbf{P}$ has a non-zero dipole moment, while isomer $\mathbf{Q}$ has a zero dipole moment.

When $\mathbf{P}$ is treated with one equivalent of triphenylphosphine (\ce{PPh3}) at 298 K in an inert solvent, it undergoes monosubstitution to form a single major product $\mathbf{Y}$ . The substitution occurs selectively at the most kinetically labile \ce{CO} ligand.

What is the Effective Atomic Number (EAN) of Ruthenium in $\mathbf{Y}$ , and what is the stereochemical arrangement of the remaining \ce{CO} ligands in $\mathbf{Y}$ ?

Options

A.
54, facial (\textit{fac})
B.
54, meridional (\textit{mer})
C.
56, facial (\textit{fac})
D.
56, meridional (\textit{mer})

Check Your Answer

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

EAN Rule (Sidgwick's Rule)|Geometric Isomerism Requirements|Optical Isomerism Logic

Why This Question Is Tricky

Common Mistakes

The question tests the intersection of the Effective Atomic Number (EAN) rule, geometric isomerism, and the kinetic trans-effect in organometallic complexes.

The hidden variable is the differential kinetic lability of identical ligands (\ce{CO}) based on their trans-partners.

Students often memorize that strong $\sigma$ -donors exert a strong trans-effect, but fail to recognize that for strong $\pi$ -acceptors like \ce{CO}, mutual competition for metal $d_{\pi}$ electrons destabilizes the bond.

If a student misidentifies the polar isomer $\mathbf{P}$ as trans, or incorrectly assumes the \ce{CO} trans to \ce{Cl^-} is more labile, they will incorrectly predict a meridional (\textit{mer}) geometry for the product.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Coordination Compounds - Class 12
Concept	EAN Rule (Sidgwick's Rule)
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free