Why only transition metals are known to form `pi` complexes ?

Explanation

To understand why only transition metals are known to form π complexes, we can break down the explanation into several steps:

### Step 1: Understanding π Complexes
- **Definition**: π complexes are formed when ligands donate their π electrons to the empty orbitals of a metal center. This interaction typically involves π bonds from the ligands.

### Step 2: Role of Ligands
- **Ligands**: Ligands that can participate in π bonding typically contain π electrons, such as those found in alkenes, aromatic compounds, or other unsaturated systems. These ligands can donate their π electrons to the metal.

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