Cyclometalated Ruthenium(II) Complexes as Highly Active Transfer Hydrogenation Catalysts

Abstract

The cyclometalated complex 2 is easily obtained in high yield from the 14-electron complex [RuCl2{(2,6-Me2C6H3)PPh2}2] (1) by reaction with formaldehyde in the presence of triethylamine. The molecular structure of 2 has been determined by an X-ray investigation and reveals a five-coordinate complex with a δ-agostic interaction of one ortho-methyl group. By displacement of one phosphane from 2, a series of new cyclometalated complexes can be obtained. The derivative 4 bearing 2-(aminomethyl)pyridine is a highly active catalyst for hydrogen transfer reactions. Thus, a large number of ketones can be quantitatively converted to alcohols with very high TOF values (up to 63000 h-1)

Cyclometalation Using d-Block Transition Metals: Fundamental Aspects and Recent Trends

“…67,270,271 Moreover, ruthenacycles are amongst the most active catalysts known to date for transfer hydrogenation reactions. 272,273 An excellent review has recently appeared, 28 which compiles a vast range of precursors and ligand settings used for cycloruthenation. Perhaps the two most important conclusions from this overview are that, first, cycloruthenation is extremely versatile and of very broad scope.…”

Cyclometalated Complexes of Ruthenium, Rhodium and Iridium as Catalysts for Transfer Hydrogenation of Ketones and Imines

“…[9] However, a few groups have recently described promising catalytic results using N À C À N, [10] P À C À P, [10a,11] C À P, [12] and C À N À N [13] cycloruthenated or cycloiridiated [14] ligands. Our contribution to this field was triggered by the discovery that cycloruthenated chiral benzylamines are also attractive catalyst precursors for the reduction of acetophenone.…”

Transfer Hydrogenation Reactions Catalyzed by Free or Silica‐Immobilized [RuCl2(ampy){RN(CH2PPh2)2}] Complexes

“…Recently, we reported the synthesis of a series of phosphanyl-Ru II complexes bearing the (2-aminomethyl)pyridine (ampy) [5][6][7][8] ligand or the related 6-(4Ј-methylphenyl)-2-pyridylmethylamine ligand, [9,10] and examined their ability to catalyze the reduction of ketones. Among complexes with the ampy ligand, exceptionally high catalytic activity was observed for complexes also bearing diphosphane ligands ( Figure 1) with the cis isomer showing higher efficiency.…”