Quinine‐Derived Imidazolidin‐2‐imine Ligands: Synthesis, Coordination Chemistry, and Application in Catalytic Transfer Hydrogenation

Two new optically active bidentate N,N‐ligands, DMIQCI (3a) and DMIQCD (3b), containing a quinuclidine core and an imidazolidin‐2‐imine unit, were synthesized. The reaction of these ligands with [(η5‐C5Me5)RuCl]4 afforded the brick‐red ruthenium(II) complexes [(η5‐C5Me5)Ru(DMIQCI)Cl] (4) and [(η5‐C5Me5)Ru(DMIQCD)Cl] (5), which were used as catalysts in the transfer hydrogenation of acetophenone in boiling 2‐propanol. The reactions of 3a and 3b with [(COD)PdCl2] (COD = 1,5‐cycloocta‐diene) and with [(DME)NiBr2] (DME = 1,2‐dimethoxyethane) afforded the square‐planar palladium(II) complexes [(DMIQCI)PdCl2] (7) and [(DMIQCD)PdCl2] (8) or the tetrahedral nickel(II) complexes [(DMIQCI)NiBr2] (9) and [(DMIQCD)NiBr2] (10), respectively. The X‐ray crystal structures of 4, 7, 9·THF, and 10 are reported.