Ruthenium catalyzed asymmetric transfer hydrogenation based on chiral P,N,O Schiff base ligands and crystal structure of a ruthenium(II) complex bearing chiral P,N,O Schiff base ligands

A ruthenium catalyst, generated in situ by heating the chiral P,N,O Schiff base ligand L (L = (S)-Ph2PC6H4CNCHPhCH2OH) with Ru(DMSO)4Cl2 in 2-propanol, is active for asymmetric transfer hydrogenation with best enantioselectivity up to 81%. A ruthenium complex of formula RuL2Cl2 is prepared and its crystal structure revealed that the two chiral P,N,O Schiff ligands are in meridional configuration. This complex is also an active catalyst for asymmetric transfer hydrogenation. However, the '[Ru(DMSO)4]Cl2 + chiral P,N,O ligand' protocol displays better enantioselectivity.