Question

ethene molecule has no lone pair of electrons yet it can form bonds with metal atom with synergic mechanism.explain(for 2 marks)

Answer 1

Asin metal-carbonyls, electrons are partially transferred from a d-orbital of themetal to anti-bonding molecular orbitals of the alkenes and alkynes. This electron-transfer (i) strengthens the metal-ligand bond and (ii) weakens the C-C bonds within the ligand. In the case of metal-alkenes and alkynes, the strengthening of the M-C₂R₄ and M-C₂R₂ bond is reflected in bending of the C-C-R angles which assume greater sp³ and sp² character, respectively. Thus strong pi-backbonding causes ametal-alkene complex to assume the character of a metallacyclopropane. Electronegative substituents exhibit greater pi backbonding.