Activation of CO₂, CS₂, and Dehydrogenation of Formic Acid Catalyzed by Iron(II) Hydride Complexes

Abstract

Fluoroarylimine‐stabilized iron(II) hydrides were used for the activation of CO2. The resulting iron(II) formate complex 6, which was obtained by formal CO2 insertion into the Fe–H bond, turned out to be unstable in solution. CO was suitable for the formation of stable analogues of complex 6. From the three‐component reaction of CO, CO2, and iron hydride, a series of stable carbonyl formate iron(II) complexes 7–9 were generated. Iron(II) formate complex 6 could also be obtained from the reaction of the iron(II) hydride complex with formic acid. On the basis of this result, the dehydrogenation of formic acid catalyzed by iron(II) hydrides was explored. The reaction was monitored by in situ 1H NMR spectroscopy, and a possible mechanism was proposed. In addition, iron(II) hydrides also reacted with CS2 to generate thiocarboxy iron(II) complexes 12, 13, 14, and 16. Unexpected complex 17 was produced from the three‐component reaction of CS2, complex 4, and compound 15. The possible mechanism of the three‐component reaction was also studied by operando IR spectroscopy.

Homogeneous Catalysis for Sustainable Hydrogen Storage in Formic Acid and Alcohols

“…Deactivation pathway of the fluoroarylimine-stabilized iron catalyst developed by Li and co-workers. (Adapted with permission from ref . Copyright 2016 John Wiley & Sons.…”

“…In the framework of their research on small-molecule activation, Wang et al reported that (bis-aryl)imine-supported iron catalysts exhibited moderate activity in FA dehydrogenation in the presence of 50 mol % NEt 3 and 10 mol % LiBF 4 , which were needed to ensure substrate activation. 264 Through variations of the nature, number, or position of the aryl substituents, complex 70 (Figure 40) emerged as the most efficient, albeit exhibiting only moderate activity and stability at 80 °C; heating for 24 h in benzene led to a maximum FA conversion of 31% and TON of 594. Under the reaction conditions, when 69 was used as the catalyst, rapid conversion to 70 was observed by 1 H NMR spectroscopy with simultaneous gas evolution.…”

Methyl Effects on the Stereochemistry and Reactivity of PPP-Ligated Iron Hydride Complexes

“…At room temperature or 80 °C, neither dihydride complex displayed any reactivity. Our attention was then turned to CS 2 , a molecule that has more reactive π-bonds . The treatment of 3 in C 6 D 6 with 2 equiv of CS 2 showed a slow insertion reaction with the hydride trans to the central phosphorus (Scheme ).…”

Recent Progress in Homogeneous Catalytic Dehydrogenation of Formic Acid

“…Although several non-precious metal catalysts for FADH have been reported, they exhibit low catalytic activity. However, various non-precious metal catalysts, including iron [37][38][39], nickel, cobalt [40,41], copper [42], and aluminum [43,44], have also been recently reported. The following is a summary of the recent notable achievements (Figure 7, Table 2).…”