Access to and Reactivity of Fe<sup>0</sup>, Fe<sup>−I</sup>, Fe<sup>I</sup>, and Fe<sup>II</sup> PC<sub>carbene</sub>P Pincer Complexes
Qingyang Wang, Richard A. Manzano, Hendrik Tinnermann, Simon Sung, Baptiste Leforestier, Tobias Krämer, Rowan D. Young
Abstract
Abstract Despite their promising metal–ligand cooperative reactivity, PC carbene P pincer ligands are rarely reported for first‐row transition‐metal centres. Using a dehydration methodology, we report access to an Fe 0 PC carbene 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 carbene P pincer ligand is also found to stabilize formal Fe II , Fe I , and Fe −I oxidation states, as demonstrated with synthesis and characterization of the complexes [ 11‐X ][BAr F 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 Fe I and Fe −I complexes contain significant carbene radical character. The ability of the PC carbene 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.