Transfer Hydrogenation Including the Meerwein‐Ponndorf‐Verley Reduction

Neutral η6-arene ruthenium complexes with monodentate P-donor ligands

“…In contrast to the extensive literature regarding the mechanism of TH with Ru complexes bearing chiral diamines and/or diphosphines [4,5,[21][22][23][24][25], there are only a handful of reports [10,12,13] with hints about the mechanism of TH with precursors of the type C. Taking into account the mechanism of TH with bidentate ligands and the strong tendency of ruthenium to form compounds with Ru H bonds, it seems reasonable to assume that the catalytically active species are ruthenium hydride complexes formed under catalytic conditions [7,8,26]. The absence of any X-H (X = N, O, S) fragment in the complex suggests that the H transfer from the donor (2-propanol) to the acceptor (acetophenone) is promoted by the metal through stepwise coordination of both donor and acceptor to the metal centre through an inner-sphere mechanism [22].…”

Hydrogen Transfer Reactions of Carbonyls, Alkynes, and Alkenes with Noble Metals in the Presence of Alcohols/Ethers and Amines as Hydrogen Donors

“…An appropriately selected donor molecule (Figure 1) provides the hydrogen of a transfer reaction. The most beneficial choice, if the donor molecule is able to coordinate to the catalytic center, allows the abstraction of hydrogen (low oxidation potential) with control by the catalyst under relatively mild conditions when the donor is not strongly bound to the catalytic center after the donation is achieved [1].…”

“…The choice of a donor molecule depends mainly on the following parameters: (a) the type of reaction (transition metal-catalyzed, MPVO catalysts, etc. ); (b) the chemical nature of the targeted functional group that is to be converted; (c) the solubility in the reaction medium (ability to act as a solvent of the corresponding reaction); (d) the influence on the equilibrium of the reaction; (e) no formation of toxic side products; (f) allows mild reaction conditions; (g) and the rate of the exchange between the metal-linked and the bulk form of the donor molecule [1].…”

“…The most beneficial choice, if the donor molecule is able to coordinate to the catalytic center, allows the abstraction of hydrogen (low oxidation potential) with control by the catalyst under relatively mild conditions when the donor is not strongly bound to the catalytic center after the donation is achieved [1].The choice of a donor molecule depends mainly on the following parameters: (a) the type of reaction (transition metal-catalyzed, MPVO catalysts, etc. ); (b) the chemical nature of the targeted functional group that is to be converted; (c) the solubility in the reaction medium (ability to act as a solvent of the corresponding reaction); (d) the influence on the equilibrium of the reaction; (e) no formation of toxic side products; (f) allows mild reaction conditions; (g) and the rate of the exchange between the metal-linked and the bulk form of the donor molecule [1].Alcohols represent the major group as source of hydrogen in transfer reactions. Primary and secondary alcohols can be used, however, based on the sigma inductive electronic effect, and secondary alcohols are better donor molecules then the primary counterparts (ethanol).…”

Breakthroughs in Hydrogen Storage—Formic Acid as a Sustainable Storage Material for Hydrogen

“…[8][9][10] Reductions of olefins, aldehydes, ketones and imines are often accomplished by catalytic hydrogen transfer from formic acid or its derivatives. [11,12] Direct decomposition of formic acid has been observed in many cases but was considered only an unwanted side reac-tion. [13,14] Indeed, all components of reversible binding and delivery of hydrogen have been at hand for some time.…”