Iron-borane catalyzed carbonyl hydroboration and isolation of an iron(I)-ketyl radical.

Grose, Laura A; Schwamm, Ryan J; Brookfield, Adam; Robinson, David; Willcox, Darren · Nat Commun · 2026

basic_science · Level V

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Abstract

Hydroboration of carbonyl compounds has proven a pivotal route to access alcohols and other C1 moieties in recent years. Despite this, iron-based catalyst systems are somewhat limited with very little mechanistic understanding of these systems developed. Here we show that an iron metalloborane complex [{(<sup>iPr</sup>DPB<sup>Ph</sup>)Fe}<sub>2</sub>(μ-1,2-N<sub>2</sub>)] (A) is an efficient pre-catalyst for hydroboration of ketones, cyclic esters and CO<sub>2</sub> with mild conditions. Mechanistic insights reveal a previously unreported direct iron(0)-mediated ligand-to-ligand hydride transfer (LLHT) process is in operation with B-H bond breaking being rate determining, indicating the importance of mechanistic studies on well-known transformations. An iron(I)-benzophenone ketyl radical with a unique S = 1 antiferromagnetic ground state has been isolated and fully characterized.