Activation of CO sub(2), CS sub(2), and Dehydrogenation of Formic Acid Catalyzed by Iron(II) Hydride Complexes

Fluoroarylimine-stabilized iron(II) hydrides were used for the activation of CO sub(2). The resulting iron(II) formate complex 6, which was obtained by formal CO sub(2) 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, CO sub(2), 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 super(1)H NMR spectroscopy, and a possible mechanism was proposed. In addition, iron(II) hydrides also reacted with CS sub(2) to generate thiocarboxy iron(II) complexes 12, 13, 14, and 16. Unexpected complex 17 was produced from the three-component reaction of CS sub(2), complex 4, and compound 15. The possible mechanism of the three-component reaction was also studied by operando IR spectroscopy. Fluoroarylimine-stabilized iron(II) hydrides were used for the activation of CO sub(2). Iron(II) formate was obtained either by CO sub(2) insertion into the Fe-H bond or from the reaction of iron(II) hydride with formic acid. The dehydrogenation of formic acid was explored with iron hydrides as catalysts. An unexpected product was generated from the reaction of CS sub(2), iron hydride, and an imine.