Question

what are pπ − pπ , dπ − pπ and dπ − dπ bonds?

Answer 1

In case of molecules, when one atom in the molecule has a vacant orbital and another atom in the molecule has lone pair of electrons, it donates the lone pair of electrons to the vacant orbitals of the atom. This type of bonds are called back-bonding. When both the vacant orbitals and the orbitals with lone pair of electrons are p orbitals they are called p π − p π. when both the vacant orbital and the orbitals with lone pair of electrons are d orbitals, then the bond is called d π − d π. p π −d π bonds are those when electrons from p orbital are donated to the vacant d-orbital.