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Q.
$ C{{N}^{-}} $ is a strong field ligand. This is due to the fact that
JamiaJamia 2011
Solution:
Cyanide ion is strong field ligand because of the presence of negative charge which makes it a stronger a donor than CO but it also weak the effectiveness of $ C{{N}^{-}} $ as a $ \pi $ acceptor. Thus, $ C{{N}^{-}} $ have the ability to form $ \sigma - $ bond and $ \pi - $ bond.