Phosphine ligands often play an important role in controlling reactivity and selectivity in transition metal catalyzed reactions. However, one common drawback of the phosphine ligands is the undesired occurrence of an interchange between P bound aryl and M bound aryl or alkyl groups in the catalytic cycle. This results in the formation of undesirable coupling products as well as changes in catalyst structure through the replacement of the phosphine ligand. This review discusses approaches to 2 understand this metathesis reaction between P-C and M-C and its productive application in catalytic reactions.