Iron‐promoted Reduction Reactions

Abstract

Iron‐promoted reduction reactions are described from the standpoint of the catalyst design. Catalysis of three well‐defined precatalysts is the first topic; iron complexes having PNNP ligands, Shvo‐type complexes, and pincer compounds are active towards catalytic hydrogenation and transfer hydrogenation of ketones. The reduction mechanisms are in line with the concept of Noyori's metal‐ligand bifunctional catalysis, in which the ligand plays a key role in the hydrogenation of the carbonyl function. The redox‐active ligands in iron‐catalyzed hydrogenation and hydrosilylation of alkenes and alkynes provide other important aspects contributing to the catalyst design. In particular, redox properties of bis(imino)pyridine ligands assist the activation of H–H and H–Si bonds in molecular hydrogen and organohydrosilanes leading to efficient hydrogenation and hydrosilylation of alkenes. Reduction reactions mediated by iron compounds, which include catalytic hydrogenation, transfer hydrogenation, and hydrosilylation, are overviewed from organic synthesis, which is promoted by a mixture of iron salts and ligands, ill‐defined catalyst precursors, and nanoparticles. From these, the possible catalyst design of iron is discussed.

Platinum-catalyzed reduction of amides with hydrosilanes bearing dual Si–H groups: a theoretical study of the reaction mechanism

“…Consequently, the outer sphere mechanisms are also ruled out catalyzed amide reduction with dual Si-H Finally, we wish to discuss the proximity effects of dual Harrod pathway was catalyzed amide reduction with BDSB. has a trigonal ), which rarely occurs in either O bond formation via the ionic outer sphere d 6 length was computed to be 1.67 Å, a value that exceeds the length of the axial Pt orbital was HOMO (Figure 1 hydrogen is highly activated due to the strong trans of the two silyl groups. Furthermore, A3b respectively, and to be Si distance and the Si and provide evidence that there is a between the two Si atoms, as a counterpart t to the Pt center ( discussed by Takagi and Sakaki with regard to a disilane bound Pt(0) N considerable amount of Pt(II) character is mixed into t ground state of complex.…”

“…3 A wide variety of transition metal compounds show catalytic activity toward hydrosilylation reactions. Among them, metal compounds, which include rhodium, 3 ruthenium, 4 and iridium complexes, 5 more ubiquitous iron, copper, zinc, and manganese compounds, 6 as well as molybdenum and rhenium oxides 7 have been investigated as catalysts for the reduction of ketones. 3 Progress in research of the hydrosilylation of carbonyl compounds led to increase of the range of substrates from aldehydes and ketones to carboxylic acid derivatives, 8 which are typically difficult to reduce by standard reduction reactions.…”

Catalyst Design of Iron Complexes

“…14a The catalytic activity of 4 was the greatest compared with other iron catalysts reported previously. 26,27 The hydrosilylation of alkenes with PMDS, catalyzed by 4, is especially important.…”

Iridium-PPh3 Catalysts for Conversion of Amides to Enamines

“…Hydrosilanes are stable metal hydrides that are useful for carbonyl reduction in the presence of Brønsted acids, Lewis acids, fluoride anion, and transition-metal catalysts . Recent progress in catalyst design to achieve high catalytic efficiency has led to the discovery of new catalysts containing not only conventional precious metals but also base metals, attracting the attention of scientists due to their environmentally benign nature . While the initial stage of studies on metal-catalyzed reduction with hydrosilanes was limited to the hydrosilylation of aldehydes and ketones, recent studies have focused on hydrosilane reduction of carboxylic acids or esters to silyl ethers as well as amides to amines .…”

“…While the initial stage of studies on metal-catalyzed reduction with hydrosilanes was limited to the hydrosilylation of aldehydes and ketones, recent studies have focused on hydrosilane reduction of carboxylic acids or esters to silyl ethers as well as amides to amines . It is known that the reduction of carboxylic acid derivatives is more difficult than that of aldehydes and ketones with conventional alumino- and borohydrides. , …”