Access to and Reactivity of Fe0, Fe−I, FeI, and FeII PCcarbeneP Pincer Complexes

Abstract

AbstractDespite their promising metal–ligand cooperative reactivity, PCcarbeneP pincer ligands are rarely reported for first‐row transition‐metal centres. Using a dehydration methodology, we report access to an Fe0 PCcarbeneP pincer complex (1) that proceeds via an isolated α‐hydroxylalkyl hydrido complex (3). Reversible carbonyl migration to the carbene position in 1 is found to allow coordination chemistry and E−H bond addition (E=H, B, Cl) across the iron–carbene linkage, representing a unique mechanism for metal–ligand cooperativity. The PCcarbeneP pincer ligand is also found to stabilize formal FeII, FeI, and Fe−I oxidation states, as demonstrated with synthesis and characterization of the complexes [11‐X][BArF20] (X=Br, I), 12, and K[13]. Compound K[13] is found to be highly reactive, and abstracts hydrogen from a range of aliphatic C−H sources. Computational analysis by DFT suggests that the formal FeI and Fe−I complexes contain significant carbene radical character. The ability of the PCcarbeneP ligand scaffold to partake in metal–ligand cooperativity and to support a range of iron oxidation states renders it as potentially useful in many catalytic applications.