Observations of rhodium-containing reaction intermediates using HPLC with ICP-MS and ESI-MS detection

HPLC with ICP-MS or ESI-MS detection has been used to investigate metal-containing reaction intermediates in the ligand exchange process leading to formation of the well known Rh-2(MEPY)(4) catalyst. A variety of intermediates are observed along the pathway to formation of the desired tetrasubstituted product, including isomeric species from di-, tri-, or tetrasubstitution that were previously believed to be absent.