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 (i Pr DPB Ph) Fe 2 (μ−1, 2-N 2) (A) is an efficient pre-catalyst for hydroboration of ketones, cyclic esters and CO 2 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.
Grose et al. (Thu,) studied this question.