The Negishi Catalysis: Full Study of the Complications in the Transmetalation Step and Consequences for the Coupling Products

Abstract

In addition to the expected products, trans- and cis- [PdRfMe(PPh3)2], the transmetalation between ZnMe2 and trans- [PdRfCl(PPh3)2] yields [PdMeCl(PPh3)2] and ZnRfMe as the result of secondary transmetalation processes. ZnRfMe is also formed by reaction of trans and cis-[PdRfMe(PPh3)2] with ZnMe2. The different competitive reaction mechanisms that participate in the transmetalations have been studied experimentally and by DFT calculations. The relative contribution of each reaction pathway in the formation of the unwanted product ZnRfMe has been measured. The effect of excess ligand (PPh3) on the several transmetalations has been stablished.