Question

Which of the following metal ion forms unstable complex with ${CN}^{-}$ :

• A. Ag(I)
• B. Zn (II)
• C. Cu (II)
• D. Cr (II)

Answer 1

The correct option is C Cu (II)

Since $d^9$ system has jahn-Teller distortion effect due to non-degensate eg. orbital, hence it does not form stable complex with cyanide ligand. Also $Cu$ is soft center so it attracts softer ligand than $CN$ like $N{H}_3,H_{2}O$ etc.