Releasing ligand rigidity in Fe(II) NNN complexes enables rapid ketone hydrosilylation with PMHS.

A low-coordinate Fe(II) complex supported by a flexible diphenylamide-based NNN pincer ligand is reported as an efficient catalyst for the hydrosilylation of ketones using polymethylhydrosiloxane (PMHS) as a sustainable reductant. The catalyst achieves near-quantitative conversion within minutes at low loading (0.1-0.5 mol%) under mild conditions, including solvent-free setups and green solvents such as 2-MeTHF and p-cymene. The system exhibits a broad substrate scope for aromatic and aliphatic ketones, with steric effects playing a major role in reaction rates. Gram-scale reactions using 0.5 mol% catalyst proceed smoothly, delivering silyl ethers in excellent isolated yields after simple workup and affording a low E-factor of 0.29. DFT calculations indicate that the conformational flexibility of the ligand facilitates substrate coordination and lowers activation barriers on the triplet surface. This work provides a practical and environmentally benign iron-catalyzed protocol for ketone hydrosilylation.