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Summary: Iron terminal imido species featuring electron-withdrawing N-substituents represent an important category of reactive metal-ligand-multiple-bond intermediates in iron-catalyzed reactions. Knowledge of them is very limited, however, as isolable complexes of this type are hard to access. Here, we report an isolable iron(IV) imido complex with trifluoromethyl on nitrogen, namely [(IPr)Fe(NC(CF3)2Ph)2]. We prepared the complex from the reaction of a low-coordinate iron(0) complex with N3C(CF3)2Ph. It has an S = 1 ground spin-state, long Fe-N(imido) bonds, and bent Fe-N(imido)-C(imido) alignments and can undergo intramolecular C–H bond activation reaction to transform into an iron(II) amido complex. Theoretical study suggests that the C–H bond activation reaction involves hydrogen-atom-abstraction mechanism and that the electron-withdrawing nature of trifluoromethyl group renders the imido ligands in [(IPr)Fe(NC(CF3)2Ph)2] and the transition state of the hydrogen-atom-abstraction step structurally close to each other, resulting in a low activation barrier.

Since 1987, the stoichiometric two-step C-H conjugate addition reactions have been developed. Herein we describe the first manganese-catalyzed one-step direct aromatic C-H conjugate addition to α,β-unsaturated carbonyls, which is accelerated by a catalytic amount of dicyclohexylamine. Experimental and computational studies substantiated the validity of the proposed catalytic cycle. [ABSTRACT FROM AUTHOR]