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Question #44584

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The Question

A researcher is investigating a diamagnetic, binuclear complex of Iron (Fe) containing terminal carbonyl (CO) and bridging nitrosyl (NO) ligands, with the general formula $\ce{Fe2(CO)_x(\mu-NO)_y}$ . The NO ligands act as 3-electron donors to the dimer.

Initially, the researcher predicts the stoichiometry $(x', y')$ by assuming the complex strictly obeys the 18-electron (EAN) rule with NO metal-metal bonds, while maintaining an octahedral geometry ( $d^2sp^3$ hybridization) around each Iron atom.

However, X-ray crystallography reveals the actual complex has the stoichiometry $(x, y)$ , maintains the $d^2sp^3$ hybridization, but contains exactly ONE Fe-Fe single bond.

What are the values of the predicted stoichiometry $(x', y')$ and the actual stoichiometry $(x, y)$ , respectively?

Options

A.
$(x', y') = (4, 4)$ and $(x, y) = (6, 2)$
B.
$(x', y') = (8, 2)$ and $(x, y) = (8, 1)$
C.
$(x', y') = (6, 2)$ and $(x, y) = (4, 4)$
D.
$(x', y') = (4, 4)$ and $(x, y) = (0, 6)$

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Numerical_Precision

Improve calculation stamina and avoid rounding errors in high-stakes competitive examinations.

Concepts Behind This Question

Valence Bond Theory Hybridization|EAN Rule (Sidgwick's Rule)|Coordination Compounds - Class 12

Why This Question Is Tricky

Common Mistakes

This problem tests the intersection of the Effective Atomic Number (EAN) rule and Valence Bond Theory (VBT) in multi-nuclear organometallic complexes.

The core trap is the dual role of a metal-metal bond: students often remember that it reduces the required Total Valence Electrons (TVE) by 2, but they frequently forget that it also occupies a physical coordination site (a hybrid orbital) in VBT.

Failing to account for the M-M bond in the Coordination Number calculation leads to incorrect stoichiometric predictions.

Additionally, it tests the knowledge of bridging NO as a 3-electron donor, distinguishing it from standard 2-electron donors.

Quick Facts About This Question

Question Information

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