● PEts and AsPh3 as ligands can form dπ−dπ bond with transition metals. ● The N−N single bond is weaker than the single P−P bond because of high inter-electronic repulsion of the non-bonding electrons. ● Nitrogen has unique ability to form pπ−pπ multiple bonds with itself, carbon and oxygen. ● Nitrogen cannot form dπ−pπ bond as other heavier elements of its group.