Novel ruthenium(ii) complexes containing imino- or aminophosphineligands for catalytic transfer hydrogenation

Abstract

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-Ph₂PC₆H₄CHNR (R = Ph (1a); 2′,6′-C₆H₃Me₂ (1b); 2′-C₆H₄OMe (1c)) lead to the chelate iminophosphine complexes [RuCl₂(κ²-P,N-2-Ph₂PC₆H₄CHNR)(PPh₃)] (R = Ph (3a); 2′,6′-C₆H₃Me₂ (3b)) and [RuCl₂(κ³-P,N,O-2-Ph₂PC₆H₄CHN-2′-C₆H₄OMe)(PPh₃)] (3c), respectively. Similarly, reactions with aminophosphine ligands 2-Ph₂PC₆H₄CH₂NHR (R = Ph (2a); ⁱPr (2d); (S)-CHMeCy (2e)) afford the 16-electron complexes [RuCl₂(κ²-P,N-2-Ph₂PC₆H₄CH₂NHR)(PPh₃)] (R = Ph (5a); ⁱPr (5d); (S)-CHMeCy (5e)). The iminophosphines 2-Ph₂PC₆H₄CHNR (R = ⁱPr (1d); (S)-CHMeCy (1e)) react with [RuCl₂(DMSO)₄] to lead to the bis-iminophosphine complexes [RuCl₂(κ²-P,N-2-Ph₂PC₆H₄CHNR)₂] (R = ⁱPr (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].