A theoretical model recently developed for describing reactions cataly
sed by transition metal complexes is applied to CO insertion in RML(n)
complexes (where M is a transition metal, R is aryl, alkyl, or anothe
r sigma-bonded ligand, and L stands for ancillary ligands). The effect
of the migrating group R, the metal M, and the number of ancillary li
gands L on the insertion step is studied. The mechanism of the double
carbonylation reactions of organic halides, catalysed by transition me
tal complexes, is analysed in the framework of the proposed model.