Access to and Reactivity of Fe 0 , Fe −I , Fe I , and Fe II PC carbene P Pincer Complexes

Despite their promising metal–ligand cooperative reactivity, PCcarbeneP pincer ligands are rarely reported for firstrow transition-metal centres. Using a dehydration methodology, we report access to an Fe0 PCcarbeneP pincer complex (1) that proceeds via an isolated a-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, Fe I, and Fe@I oxidation states, as demonstrated with synthesis and characterization of the complexes [11-X]-[BArF 20] (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 application