Access to and Reactivity of Fe , Fe , Fe , and Fe PC P Pincer Complexes.

Despite their promising metal-ligand cooperative reactivity, PC P pincer ligands are rarely reported for first-row transition-metal centres. Using a dehydration methodology, we report access to an Fe PC P 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 PC P pincer ligand is also found to stabilize formal Fe , Fe , and Fe oxidation states, as demonstrated with synthesis and characterization of the complexes [11-X][BAr ] (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 Fe and Fe complexes contain significant carbene radical character. The ability of the PC P 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.