Design of Manganese Phenol Pi‐complexes as Shvo‐type Catalysts for Transfer Hydrogenation of Ketones

Abstract

Catalytic hydrogenation is one of the most important reactions both in academic research and industry. We explored ability of the manganese pi‐complexes to act as Shvo‐type catalysts for transfer hydrogenation of ketones. DFT calculations suggested that the transfer of hydrogen atoms from the hypothetical intermediate [(C6Me3H2OH)Mn(CO)2H] to acetone has low activation barrier of 10.9 kcal mol−1. Experimentally a number of ketones with various functional groups (OMe, NH2, Cl, CF3, pyridyl) were successfully reduced in isopropanol at 90 °C in the presence of the complex [(C6Me3H2OH)Mn(CO)3]BF4 (1 mol %) and tBuOK (75 mol %). However, further investigation revealed that the reduction was mainly promoted by base rather than the manganese complex.

Mechanistic Complexity of Asymmetric Transfer Hydrogenation with Simple Mn–Diamine Catalysts

“…In addition, first-row TM catalysts exhibit striking reactivity patterns unprecedented in hydrogenation catalysis. ,,, A chemically distinct feature of some manganese hydrogenation catalysts is that they do not rely on commonly employed strong donor ligands such as phosphines. , Indeed, for Mn, the introduction of simple bi- or tridentate nitrogen-donor ligands was sufficient to promote hydrogenation of carbon dioxide to formate and formamide and transfer hydrogenation of CX bonds (X = O, N), e.g., ketones, imines, and aldimines. − …”

Diagonal Relationship among Organometallic Transition-Metal Complexes

“… At the same time, the hypothetical η 6 -phenol manganese­(I) complex [(η 6 -C 6 H 5 OH)­Mn­(CO) 2 H] ( 35 ) was theoretically proposed as a Shvo-type catalyst for the transfer hydrogenation of ketones (Figure ). Ketone reduction was attempted using the manganese complex [(η 6 -C 6 Me 3 H 2 OH)­Mn­(CO) 3 ]­BF 4 (1 mol %) in the presence of t BuOK (75 mol %) in isopropanol at 90 °C, and such a reduction was mainly promoted by the added base; the treatment of [(η 6 -C 6 Me 3 H 2 OH)­Mn­(CO) 3 ]­BF 4 with t BuOK produced no manganese­(I)-hydride species as the proposed active species …”

“…87 At the same time, the hypothetical η 6phenol manganese(I) complex [(η 6 -C 6 H 5 OH)Mn(CO) 2 H] (35) was theoretically proposed as a Shvo-type catalyst for the transfer hydrogenation of ketones (Figure 7). 88 Ketone reduction was attempted using the manganese complex [(η…”

“…2 OH)Mn(CO) 3 ]BF 4 with t BuOK produced no manganese(I)-hydride species as the proposed active species 88. ■ CONCLUSIONThis tutorial describes a diagonal relationship of organometallic transition-metal complexes.…”

Catalytic Transfer Hydrogenation of Levulinic Acid to γ-Valerolactone over Ni3P-CePO4 Catalysts

“…The MPV reduction, a method of carbonyl group reduction using alcohols as hydrogen donors, can be operated at moderate reaction conditions. , Various catalysts based on noble metals, − transition metals, − metal complexes, , hydrotalcites, metal oxides and hydroxides, − and metal–organic hybrids have been investigated for MPV reduction. However, some inevitable disadvantages existed in these catalysts, for example, high expense of non-renewable raw materials, complicated preparation process, harsh reaction conditions (high temperature and long time), and low yield of desired products .…”