$\mathrm{PEt}_3$ and $\mathrm{AsPh}_3$ as ligands can form $$\mathrm{d} \pi-\mathrm{d} \pi$$ bond with transition metals

The $$\mathrm{N}-\mathrm{N}$$ single bond is as strong as the $$\mathrm{P}-\mathrm{P}$$ single bond

Nitrogen has unique ability to form $p \pi-p \pi$ multiple bonds with nitrogen, carbon and oxygen

Nitrogen cannot form $$\mathrm{d} \pi-\mathrm{p} \pi$$ bond as other heavier elements of its group