Among the following complexes, the one showing the highest rate of substitution of a CO ligand on heating… · ABC26IN0286

Subject: Inorganic Chemistry · Chapter: Organometallic Compounds · Topic: Organometallic Compounds – General · Exam: CSIR NET 2020 · Marks: 2 · Difficulty: Medium

Among the following complexes, the one showing the highest rate of substitution of a CO ligand on heating with one equivalent of $\mathrm{PPh_3}$ in decalin, is
(a)$(\eta^5\text{-}\mathrm{C_5H_5})\mathrm{Mn(CO)_3}$
(b)$(\eta^5\text{-}\mathrm{C_5Ph_5})\mathrm{Mn(CO)_3}$
(c)$(\eta^5\text{-}\mathrm{C_5Me_5})\mathrm{Mn(CO)_3}$
(d)$(\eta^5\text{-indenyl})\mathrm{Mn(CO)_3}$
Answer
Answer (as printed): D
Explanation
The highest rate of substitution of a CO ligand on heating with PPh3 is easy where slippage of haptacity is easy. For slippage is easy because it is not at the cost of aromatic character (η5 → η3). But η5 – Cp* , complexes, rate decreases because with respect Cp slippage of haptacity is due to at the cost of aromatic character.

Explanation as extracted from the printed page; notation may be imperfect.

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