text: The insertion of carbon monoxide and alkenes into metal-carbon bonds is a widely exploited reaction with major industrial applications.
  Such reactions are subject to the usual parameters that affect other reactions in coordination chemistry, but steric effects are especially important in determining the stereochemistry and regiochemistry of the reactions. The reverse reaction, the de-insertion of CO and alkenes, are of fundamental significance in many catalytic cycles as well.
  Widely employed applications of migratory insertion of carbonyl groups are hydroformylation and the carbonylative production of acetic acid.  The former converts alkenes, hydrogen, and carbon monoxide into aldehydes.  The production of acetic acid by carbonylation proceeds via two similar industrial processes.  More traditional is the rhodium-based Monsanto acetic acid process, but this process has been superseded by the iridium-based Cativa process.  By 2002, worldwide annual production of acetic acid stood at 6 million tons, of which approximately 60% is produced by the Cativa process.
  The Cativa process catalytic cycle, shown above, includes both insertion and de-insertion steps.  The oxidative addition reaction of methyl iodide with (1) involves the formal insertion of the iridium(I) centre into the carbon-iodine bond, whereas step (3) to (4) is an example of migratory insertion of carbon monoxide into the iridium-carbon bond.  The active catalyst species is regenerated by the reductive elimination of acetyl iodide from (4), a de-insertion reaction.