S = 3/2 Iron(I)‐Bisphosphine‐Ate Complexes: Synthesis, Characterization, and Reactivity for Electrophile Activation

ABSTRACT Iron bisphosphine complexes represent an important class of sustainable catalysts for a variety of important chemical transformations due to the high abundance, low toxicity, and redox‐rich chemistry inherent to iron‐based systems. In particular, transient, low‐coordinate Fe(I) species are postulated to play a pivotal role in multiple catalytic transformations as the principal species for C─X bond activation (X = Cl, Br, I). However, insight into the electronic structure, bonding, and reactivity of Fe(I)‐bisphosphine complexes remains poorly developed. In the present study, we report the development of four‐coordinate (4C), high‐spin ( S = 3/2) Fe(I)‐bisphosphine‐ates. Several novel Fe(I) complexes were structurally characterized, and their electronic structure and bonding were evaluated using a combined spectroscopic, synthetic, and computational approach. Additionally, this study highlights the potential role of charged species in synthetically relevant contexts via in situ formation of (4C) Fe(I)‐bisphosphine‐ates in the presence of ubiquitous additives (e.g. MgBr 2 ). Lastly, we demonstrate the utility of these Fe(I)‐bisphosphine‐ates toward rapid C─X homolytic cleavage of common alkyl‐ and aryl‐halide electrophiles, as well as the ability to serve as synthons for further development of new high‐spin Fe(I)‐bisphosphine‐ate complexes through transmetalation.