Ligands that can interact with a metal center by forming a -bond are commonly called -acids and

Ligands that can interact with a metal center by forming a π-bond are commonly called π-acids and p-bases. The definitions of π-acid and π-base are similar to those used for Lewis acidity. A π-acid is a ligand that can accept electrons by using π-orbitals, and a π-base donates electrons by using π-orbitals.

(a) On the basis of these definitions, describe each of the following ligands as either a π-acid, a π-base, or neither: (i) CN^–; (ii) Cl^–; (iii) H₂O; (iv) en.

(b) Place them in order of increasing ligand field splitting.