Ruthenium complexes of P-stereogenic phosphines with a heterocyclic substituent. Issue 20 (27th April 2016)

• Record Type: Journal Article
• Authors: Clavero, Pau; Grabulosa, Arnald; Rocamora, Mercè; Muller, Guillermo; Font-Bardia, Mercè
• Is Part Of: Dalton transactions. Volume 45:Issue 20(2016)
• Page Start: 8513
• Page End: 8531
• Publication Date: 2016-04-27
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c6dt00995f
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Optically pure P -stereogenic monophosphorus ligands containing a heterocyclic substituent have been prepared. They have been coordinated to Ru-η 6 -arene moieties in which the ligands act as mono- or bidentate. The complexes catalyse asymmetric transfer hydrogenation reactions with up to 70% ee. Abstract : The synthesis via phosphine-boranes of 13 new optically pure P -stereogenic diarylphosphines P(Het)PhR (Het = 4-dibenzofuranyl (DBF), 4-dibenzothiophenyl (DBT), 4-dibenzothiophenyl- S, S -dioxide (DBTO2 ) and 1-thianthrenyl (TA); R = OMe, Me, i-Pr, Fc (ferrocenyl)) following the Jugé–Stephan method is described. The ligands were designed with the aim of having a heteroatom in a position capable of interacting with a metal upon coordination. The ligands and their precursors have been fully characterised, including the determination of two crystal structures of phosphine-boranes. Ru neutral complexes of the type [RuCl2 (η 6 -arene)(κ P -P )] (arene = p -cymene and methyl benzoate) have been prepared and characterised, including three crystal structure determinations. Treatment of solutions of the complexes with TlPF6 allowed the preparation of well-defined cationic complexes [RuCl(η 6 -arene)(κ 2 P, S -P )]PF6 for DBT- and TA-based phosphines. The complexes possess a stereogenic Ru atom and in most of the cases they are present as a single isomer in solution. All the Ru complexes have been used in the asymmetric transfer hydrogenation of acetophenone in refluxing 2-propanol, with good activities and up to 70% ee.