PNNP Macrocycles: A New Class of Ligands for Asymmetric Catalysis

We report the first examples of enantiomerically pure P₂N₂ macrocycles containing either a diimino (1a) or diamino donor set, as well as their ruthenium(II) dichloro complexes. Unexpectedly, the diimino derivative 2a is a more efficient catalyst in the transfer hydrogenation of acetophenone than its diamino analogue.