Understanding Rh‐catalysed Hydroformylation with Phosphite Ligands through Catalyst Speciation Analysis by Operando FlowNMR Spectroscopy

Abstract

AbstractPhosphites are industrially important ligands for the Rh‐catalysed hydroformylation of olefins because they produce more active catalysts than phosphines, which is mainly due to their strong π‐acceptor properties facilitating CO dissociation from the metal centre. Herein, the effect of three prominent phosphite ligands (triphenylphosphite, Alkanox and BiPhePhos) on catalyst speciation during turnover is investigated using multi‐nuclear operando FlowNMR spectroscopy. The quantitative catalyst distribution maps derived explain activity trends across a range of catalytic reaction conditions that show how phosphites produce more active catalysts, including reduced formation of inactive Rh0 dimers in the absence of substrate during pre‐activation and at the end of the reaction. Additionally, [(alkanox)Rh(acac)] complexes have been found to be of high stability which can be exploited for post‐catalytic Rh recovery by simple addition of 2,4‐pentanediones.