Question

I need to get a brief explanation on the phenomenon of back bonding in a lucid manner with examples.. Please

Answer 1

Back bonding is the phenomena where elcetrons from a more electronegative element are trasnferred to lesser electronegative element. This happens when orbitals of more electronegative element are empty and can accomodate electrons from the more electronegative element.
It occurs in many cases, most common being the case of organometallic compounds where electrons from the metal are used to bond to the ligand, in the process relieving the metal of excess negative charge.
Some, cases like that of BF3 also shows back bonding as in BF3 boron has sp2 hybridization and is a planar molecule .the fluorine atom has three lone pairs of electrons in the 2p orbital. Due to the small size of fluorine atom and strong repulsions pΠ- pΠ back bonding takes place .Due to this pΠ- pΠ back bonding B-F bond acquires some kind of double bond nature. (Here both boron and fluorine had electrons in 2p orbital so it was easy to transfer electron)
Talking of the elements , Carbon takes part in back bonding as CO,-NC, alkenes and alkynes, nitrogen as NO (all ligand), Phoshphorus as phosphine.
Back bonding in organo-metallic compounds.7