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

Article abstract of DOI:10.1002/cctc.201900952

Set of [Ru(η⁶-cymene)(R)XCl] (R=L¹SnCl, L¹GeCl L²PPh₂, X=Cl or SnCl₃, L¹=[2-(CH₂NEt₂)-4,6-(tBu)₂C₆H₂]^?, L²=2,6-iPr₂-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(η⁶-cymene)(L²PPh₂)Cl₂] (3) with least negative charge on the Ru atom has been observed as the most effective. The design of the phosphine ligand L² 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.