Novel ruthenium(II) complexes containing imino- or aminophosphine ligands for catalytic transfer hydrogenation

Five- and six-coordinate ruthenium(II) complexes containing imino- and aminophosphines have been prepared by ligand exchange processes. Thus, reactions of [RuCl2 (PPh3)(3)] with 2-Ph2PC6H4CH = NR (R = Ph (1a); 2',6'-C6H3Me2 (1b); 2'-C6H4OMe (1c)) lead to the chelate iminophosphine complexes [RuCl2 (kappa(2)-P,N-2Ph(2) PC6H4CH= NR) (PPh3)] (R = Ph (3a); 2',6'-C6H3Me2 (3b)) and [RuCl2 (kappa(3)-P,N,O-2-Ph2PC6H4CH= N-2'-C6H4OMe) (PPh3)] (3c), respectively. Similarly, reactions with aminophosphine ligands 2-Ph2PC6H4CH2NHR (R = Ph (2a); Pr-i (2d); (S)-CHMeCy (2e)) afford the 16-electron complexes [RuCl2 (k(2)-P,N-2-Ph2PC6H4CH2NHR) (PPh3)] (R = Ph (5a); Pr-i (5d); (S)-CHMeCy (5e)). The iminophosphines 2-Ph2PC6H4CH=NR (R = Pr-i (1d); (S)-CHMeCy (1e)) react with [RuCl2 (DMSO)(4)] to lead to the bis-iminophosphine complexes [RuCl2 (k(2)-P,N-2-Ph2PC6H4CH = NR)(2)] (R = Pr-i (4d); (S)-CHMeCy (4e)). The crystal structure of 4d has been determined by X-ray diffraction. Complexes 3a-c, 4d,e and 5a,d,e are active in catalytic transfer hydrogenation of acetophenone. All of them are more efficient than the precursor [RuCl2 (PPh3)(3)].