Heterobimetallic Cu(I)–Rh(I) and Cu(I)–Ir(I) Complexes: Synthesis, Catalytic Applications in Transfer Hydrogenation, and Photophysical Properties

The syntheses and structural characterization of Cu(I)–Rh(I) and Cu(I)–Ir(I) complexes are reported. These complexes are synthesized via the reaction of a previously reported copper amidinate complex, Cu 2 L 2 (L= {Ph 2 PC≡CC(NDipp) 2 }, Dipp = N , N ′‐2,6‐diisopropylphenyl), with [M(cod)Cl] 2 , (M= Rh, Ir; cod = 1,5‐cyclooctadiene) yielding complexes [{(M(cod)Cl)Ph 2 PC≡CC(NDipp) 2 } 2 Cu 2 ] (M= Rh, Ir). Additionally, an alternative one‐pot synthetic route is explored by the reaction of lithium salt of the ligand, [M(cod)Cl] 2 , (M= Rh, Ir), and CuCl, resulting in improved yields of [{(M(cod)Cl)Ph 2 PC≡CC(NDipp) 2 } 2 Cu 2 ]. Further, reaction of lithium salt of the ligand with [M(cod)Cl] 2 , (M= Rh, Ir) leads to the formation of intermediate complexes [{(M(cod)Cl)Ph 2 PC≡CC(NDipp) 2 }Li(thf) 3 ] (M= Rh, Ir), which upon hydrolysis, yielded protonated amidinate derivatives [(M(cod)Cl)Ph 2 PC≡CC(NDipp)(NHDipp)] (M= Rh, Ir). In the second pathway, lithium salt of the ligand is hydrolyzed to obtain [Ph 2 PC≡CC(NDipp)(NHDipp)] 2 and further reaction with [M(cod)Cl] 2 , (M= Rh, Ir) yields [(M(cod)Cl)Ph 2 PC≡CC(NDipp)(NHDipp)] via an alternative reaction pathway. The catalytic potential of Cu(I)–Ir(I) complex [{(Ir(cod)Cl)Ph 2 PC≡CC(NDipp) 2 } 2 Cu 2 ] is evaluated for transfer hydrogenation (TH) of aryl aldehydes using isopropanol as a hydrogen transfer source. Furthermore, the Ir complexes [{(Ir(cod)Cl)Ph 2 PC≡CC(NDipp) 2 } 2 Cu 2 ] and [(Ir(cod)Cl)Ph 2 PC≡CC(NDipp)(NHDipp] are found to be luminescent in the solid state at 77 K with an emission maximum around 580 nm.