Highly Active and Selective Ru-PNH Catalyst in Aerobic Oxidation of Benzyl Amines

Set of [Ru(eta(6)-cymene)(R)XCl] (R=(LSnCl)-Sn-1, (LGeCl)-Ge-1 (LPPh2)-P-2, X=Cl or SnCl3, L-1=[2-(CH2NEt2)-4,6-(tBu)(2)C6H2](-), L-2=2,6-iPr(2)-C6H3-NH-) catalysts was tested in aerobic oxidations of primary amines. The activity of studied catalysts depends on the charge of the Ru atom that has been influenced either by donating ligands R or by character of X. Typical Ru/P catalyst [Ru(eta(6)-cymene)((LPPh2)-P-2)Cl-2] (3) with least negative charge on the Ru atom has been observed as the most effective. The design of the phosphine ligand L-2 containing amino-phosphine PNH moiety provided efficient anchoring of complex 3 to silica gel via hydrogen bonding of the PNH functional group to SiO2 to give heterogeneous catalyst 3-silica. This complex has been also efficiently tested in aerobic oxidation as recyclable catalyst with cumulative TON up to 6930.