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Question #44908

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The Question

Consider the reaction of \textit{trans}-dichloridobis(tricyclohexylphosphane)palladium(II) with excess \ce{KSCN} in a suitable solvent at 298 K. The reaction yields a thermodynamically stable, mononuclear square planar complex $X$ .

Given:

\ce{Pd^{2+}} is a soft Lewis acid.
The Tolman cone angle of tricyclohexylphosphane (\ce{PCy3}) is $170^\circ$ .
The \ce{M-N-C} bond angle in N-bonded thiocyanate is $\approx 180^\circ$ , whereas the \ce{M-S-C} bond angle in S-bonded thiocyanate is $\approx 100^\circ$ .

According to IUPAC 2005 recommendations, what is the correct IUPAC name of complex $X$ ?

Options

A.
\textit{trans}-dithiocyanato- $\kappa N$ -bis(tricyclohexylphosphane)palladium(II)
B.
\textit{trans}-bis(tricyclohexylphosphane)dithiocyanato- $\kappa N$ -palladium(II)
C.
\textit{trans}-dithiocyanato- $\kappa S$ -bis(tricyclohexylphosphane)palladium(II)
D.
\textit{trans}-bis(tricyclohexylphosphane)dithiocyanato- $\kappa S$ -palladium(II)

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Step-by-Step Solution

Explanation

How the Examiner Thinks

Exception_Exposure

Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.

Concepts Behind This Question

IUPAC Nomenclature Priority|Nucleophilic Addition Sterics

Why This Question Is Tricky

Common Mistakes

This question tests the student's ability to decouple thermodynamic HSAB rules from steric constraints in coordination chemistry.

Students often blindly apply the HSAB principle (\ce{Pd^{2+}} is soft -> S-bonding) without considering the physical geometry of the binding modes (bent vs linear) and the steric bulk of auxiliary ligands (Tolman cone angle).

Furthermore, it tests a subtle IUPAC nomenclature rule: multiplicative prefixes that are intrinsic to the ligand's name (like 'tri' in tricyclohexylphosphane) MUST be included in alphabetical sorting, unlike prefixes indicating the number of ligands (like 'bis' or 'di').

Quick Facts About This Question

Question Information

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