Catalytic cleavage of C(sp2)-H bond is a key ingredient to achieve structural diversity and plays an important role in chemical synthesis. Computational studies have shown that the multi-state reactivity is likely to be responsible for the C(sp2)-H activation step in arylation of α-benzoquinoline with inexpensive and non-toxic iron-based catalysts, which proceeds at remarkably low temperatures (i.e. 0 °C to room temperature). In this study, the roles of different spin-states of Fe(II) in the C(sp2)-H bond activation is investigated in the gas phase and the tetrahydrofuran solvent using different density functionals and coupled cluster methods. The results demonstrate that the multi-state reaction mechanism involving transitions between quintet, triplet and singlet electronic states is thermodynamically superior to the single-state quintet pathway. This “spin-forbidden” multi-state reaction mechanism explains the very mild conditions of the C(sp2)-H activation by ferrous catalyst. This work will facilitate the design of a new class of catalysts based on earth-abundant transition metals and utilizing novel reaction mechanisms involving multiple electronic states of different spin multiplicities. Such catalysts are highly relevant for converting petroleum-derived hydrocarbons to valuable chemicals.

Iron-catalyzed multi-state activation of C(sp2)–H bond

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.