Decomposition pathways of homogeneous catalysts

Homogeneous catalysts can decompose in a variety of ways: metal deposition, ligand decomposition, reaction with impurities, dimer formation, and reaction of the metal center with the ligand. Sometimes these side reactions lead to temporary deactivation only and the catalyst activity can be restored. Without attempting to be complete, I have collected a range of examples of catalyst decomposition. Our examples will concentrate on homogeneous reactions of commercial interest, such as polymerization, oxidation, oligomerization, hydroformylation, carbonylation, hydrocyanation, and cross-coupling reactions.