Photochemical Synthesis of Triiron Oxycarbyne Clusters

Under photochemical conditions, triiron oxycarbyne complexes, Cp₃Fe₃(CO)₃(COR) (Cp = cyclopentadienyl; R = dimethylphenylsilyl or pinacolatoboryl), can be generated by reducing [CpFe(CO)₂]₂ (Fp₂) with dimethylphenylsilane or pinacolborane. This method achieves partial CO reduction in a single step, using silane or borane as sole sources of electrons and electrophiles. The Cp₃Fe₃(CO)₃(COR) complexes were characterized by spectroscopic methods and X-ray crystallography, revealing elongated C-O bonds in the μ₃-COR moiety consistent with single-bond character. Bonding analysis through density functional theory calculations establishes these oxycarbyne ligands as XZ₂-type based on the covalent bond classification system, differing from classic Fischer and Schrock-type carbynes. Initial mechanistic investigations combined with relevant literature precedents provided hints for the triiron oxycarbyne formation pathway.