Substitution of L with other ligands will be easiest for the species
(a)
(b)
(c)
(d)
Answer
Answer: C ✓ checked by 4AB · confidence high
Explanation
Indenyl effect: η⁵ → η³ ring slippage restores the benzene ring's aromaticity, opening a site for associative substitution. Indenyl complexes substitute far faster than Cp, Cp* or arene complexes (c).