Acetate Acetylacetonate Ampy Ruthenium(II) Complexes as Efficient Catalysts for Ketone Transfer Hydrogenation

Abstract

The mixed acetate acetylacetonate (acac) ruthenium(II) phosphine complexes Ru(OAc)(acac)P2 [P2=(PPh3)2, Ph2P(CH2)4PPh2 (dppb)] were prepared by protonation of Ru(OAc)2(PPh3)2 with acetylacetone in dichloromethane. Reaction of the dppb derivative with 2‐(aminomethyl)pyridine (ampy) affords the complex Ru(OAc)(acac)(ampy)(dppb), which converts to [Ru(acac)(ampy)(dppb)](OAc) in toluene at 90 °C. In the former derivative the ampy ligand is monodentate and coordinates through the NH2‐moiety. The isolated acac complexes are active catalysts for the transfer hydrogenation of ketones with loadings as low as 0.01 mol%, the ampy having a strong accelerating effect. Several aromatic and aliphatic ketone substrates are converted to their corresponding alcohols, and different electronic influences through substituents on acetophenone are tolerated.

Recent Advances in Ru Catalyzed Transfer Hydrogenation and Its Future Perspectives

“…Anderson and co-workers have reported extremely active proline based 2-aza-norbornyl amino alcohol ligands (Figure 4) for the ATH process. The [Ru(p-cymene) (13)] in presence of i PrOH catalyzed TH of acetophenone with S/C = 1000 to give ca. 97% conversion, ca.…”

“…These catalysts were highly selective to aromatic ketones over to aliphatic and aldehyde groups and showed efficient conversion (ca. 100%) of acetophenone to 1-phenylethanol in Blueprint of aza-norbornyl amino alcohol ligands (12,13) and low energy TS (13a) determined theoretically involving remote dipole interactions (Ref. [8]).…”

“…The second step was the coordination of i PrOH with the six-member TS (B). The third step was the formation of Ru-H species (C), which formed the substrate coordinated TS (D) and finally upon transfer of hydrogen led to the regeneration of species A [13].…”

“…Figure 4.Blueprint of aza-norbornyl amino alcohol ligands(12,13) and low energy TS (13a) determined theoretically involving remote dipole interactions (Ref [8]…”

Bulky Diphosphine Acetate Ruthenium Complexes: Synthesis and Catalytic Activity in Ketone Transfer Hydrogenation and Alkyne Dimerization

“…The presence of a CO ligand increases stability, retarding the catalyst deactivation that may occur through substrate decarbonylation. , It is worth pointing out that carboxylates are not innocent ligands and can play a pivotal role in catalysis (i.e., proton acceptors for H 2 splitting), as well as in the preparative scope, stabilizing monomeric species by switching from mono- to bidentate mode. Thus, ruthenium carboxylate complexes were found to catalyze the HY of the olefinic, , carbonyl, and carboxylic compounds, alcohol dehydrogenation, and TH . In addition, a higher activity in the TH has been observed for acetate vs chloride pincer complexes [RuX­(CNN)­(dppb)] (X = Cl, OAc) .…”