On the mechanism of cis‐ligand insertion

For reactions of the type magnified image L‐O, generally called “cis‐ligand insertion”, there is increasing experimental evidence that the group<//UEQN> Q migrates. The present paper gives a theoretical analysis of this rearrangement, which is illustrated by the specific example of the growth reaction in Ziegler polymerizations of a‐olefins: magnified image As a first approximation to the reaction path the angular vibrabtion of R is analysed from a quantum‐mechanical point of view, showing the role that d orbitals in transition‐metal compounds play in the migration of alkyl groups to π‐bonded olefins. It appears that the migrating ligands finds a suitable combination of orbitals to remain bonded to the complex all along the reaction coordinate.