Treatment of (5-C 5H 5) 2Ni with Na/Hg in ethanol gives major product .

$(\eta^5-C_5H_5)(\eta^3-C_5H_5)Ni$

GATE 2023 CY – Question 41

Inorganic Chemistry · Organometallics: 18-Electron rule; metal-alkyl, metal-carbonyl, metal-olefin and metal-carbene complexes and metallocenes. Fluxionality in organometallic complexes. Types of organometallic reactions. Homogeneous catalysis – Hydrogenation, hydroformylation, methanol to acetic acid process, olefin metathesis and Wacker oxidation. Heterogeneous catalysis – Fischer-Tropsch reaction, Ziegler-Natta polymerization. · 2 marks · Multiple choice

Treatment of $(\eta^5-C_5H_5)_2Ni$ with Na/Hg in ethanol gives major product ______.

$(\eta^5-C_5H_5)(\eta^3-C_5H_5)Ni$
$(\eta^3-C_5H_5)_2Ni$
$(\eta^5-C_5H_5)(\eta^3-C_5H_7)Ni$
$(\eta^3-C_5H_7)_2Ni$

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (C) $(\eta^5-C_5H_5)(\eta^3-C_5H_7)Ni$

Explanation

Reduction and protonation hydrogenate one Cp ring to C5H7 while the other retains η5 coordination. The new ring binds as an η3 allyl fragment. Electron count is Ni(II)d8+Cp6e+allyl4e=18e, consistent with **(η5-C5H5)(η3-C5H7)Ni, C**. A/B only alter hapticity without the protonation chemistry.