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

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 H-1 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.