P-Stereogenic threonine derived Ir–P,N complexes. Reversiblecyclometallation and asymmetric hydrogenation reactions

Abstract

A threonine-derived phosphine-oxazoline iridium catalyst is reported, showcasing excellent selectivity in thehydrogenation of N-Boc-2,3-diarylallylamines. The reversible cyclometallation process between the squareplanar Ir(I) complex and the corresponding octahedral Ir(III) species is thoroughly investigated, while consideringthe influence of substitution at the phenyl group of the oxazoline on this equilibrium. X-Ray analysis revealsthat the cyclometallated tridentate ligand adopts a fac coordination mode. Furthermore, the catalyticperformance of these complexes in the asymmetric hydrogenation is evaluated and the utilization of Ir(III) precatalystsor Ir(I)/Ir(III) mixtures in hydrogenation reactions is proposed based on the observed equilibriumdynamics.