Functional phosphines XV. Ruthenium complexes containing C 5H 8(PR 2) 2 and [formula omitted] ligands (R = Me, Ph, OPh; R′ = H, Me): synthesis and application to homogeneous [lbond2]C [dbnd]O hydrogenation and transfer hydrogenation

Abstract

Treatment of [Ru(η 4-C 8H 12){η 3-(CH 2) 2CMe} 2] with C 2 chiral cyclopentane-1,2-diyl-bis(phosphines) trans-1,2-C 5H 8(PR 2) 2 in hexane afforded the chelate complexes [Ru{η 3-(CH 2) 2CMe} 2{1,2-C 5H 8(PR 2) 2}], where R = Me ( 2), Ph ( 3), NC 5H 10 ( 4), and OPh ( 5). The mixed-ligand compounds [ RuCl 2 { 1 , 2 - C 5 H 8 ( PR 2 ) 2 } ( Ph 2 PCH 2 CR 2 ′ NH 2 ) ] [R′ = H: R = Me ( 6), Ph ( 7), OPh ( 8); R′ = Me: R = Ph ( 9)] were obtained by reactions of the bis(2-methylallyl) precursors 2, 3, and 5 with methanolic HCl in acetone, followed by the addition of the required aminophosphine in DMF. The ( P∩ P) 2- and ( P∩ N) 2-chelated complexes [RuCl 2{1,2-C 5H 8(PMe 2) 2} 2] ( 1) and [RuCl 2(Ph 2PCH 2CMe 2NH 2) 2] ( 10) resulted from RuCl 3 · 3H 2O and 1,2-C 5H 8(PMe 2) 2 or Ph 2PCH 2CMe 2NH 2 under reducing conditions. The crystal structures of 1, 3, 4, 6, 7, 9, and 10 were determined by single-crystal X-ray diffraction. Complexes 7, 9, and 10, activated by KOBu- t, i-PrOH, were used as catalysts for the transfer hydrogenation of acetophenone with i-PrOH as the hydrogen source. Base modified complex 10 also turned out to be an active catalyst for the direct hydrogenation of the ketone by H 2 under pressure.