The catalytic activity of transition elements is related to their :

The ability of transition elements to adopt multiple oxidation states and form complexes is attributed to their catalytic activity. Transition metals exhibit catalytic behaviour for the following reasons.

 The presence of unoccupied d orbitals. They have the ability to have varying valencies. They have a proclivity for forming complex compounds.

The ability of transition metals and their compounds to adopt multiple oxidation states and complexes is attributed to their catalytic activity.