Hydrogen Isotope Exchange with Iridium(I) Complexes Supported by Phosphine‐Imidazolin‐2‐imine P,N Ligands

Abstract

Abstract Phenylene‐bridged hybrid phosphine‐imidazolin‐2‐imine R P,N R′ ligands (R=Ph, Cy, i‐ Pr, t‐ Bu; R′=Me, i‐ Pr) were prepared from 1,2‐dibromobenzene by palladium‐catalyzed C–N coupling with 1,3,4,5‐tetramethylimidazolin‐2‐imine or 1,3‐diisopropyl‐4,5‐dimethylimidazolin‐2‐imine, followed by lithiation with tert ‐butyllithium and reaction with the chlorophosphines (R 2 PCl). Their reaction with the dimeric iridium complex [Ir(cod)Cl] 2 (cod=1,5‐cyclooctadiene) and subsequent anion exchange with sodium tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate (NaBArF 24 ) or potassium hexafluorophosphate (KPF 6 ) afforded iridium complexes of the type [( R P,N R′ )Ir(cod)]BArF 24 or [( R P,N R′ )Ir(cod)]PF 6 , respectively. The latter PF 6 salts were structurally characterized, revealing short Ir—N bonds as an indication of electron‐rich nitrogen donor atoms. The former complexes were tested for their applicability in catalytic H/D exchange. In particular, the complex with the ligand t‐ Bu P,N Me showed remarkable performance in H/D exchange with a broad range of aromatic substrates, including ketones, amides, esters, heterocycles and nitro compounds, and also promoted H/D exchange at aromatic Boc‐protected amines, benzylamines and methoxy derivatives. magnified image