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Q.
Among the following, the $\pi$-acid ligand is
KVPYKVPY 2010Coordination Compounds
Solution:
The $\pi$-acid ligands are those ligands, which have filled orbitals that can donate electrons to metals and also have empty anti-bonding orbitals, which can also accept electrons from the central metals. Among the given options $CN$ is a $\pi$-acid ligand.