Merging cyclopentadienone tuning and CO to isonitrile substitution to develop photo-activated iron cyclopentadienone catalysts

This study explores the development and reactivity of novel iron cyclopentadienone complexes incorporating isonitrile ligands for photo-activated borrowing hydrogen (BH) catalysis. By merging strategies of cyclopentadienone tuning with isonitrile functionalization, this work aims to enhance the efficiency of photoactivation processes. New complexes featuring 4-nitrophenyl isonitrile ligands combined with electron-rich cyclopentadienones (L² and L³) were synthesized and characterized through X-ray crystallography, IR, and Mössbauer spectroscopy. Despite promising structural and electronic properties, these complexes showed reduced catalytic activity compared to classical Knölker-type analogues under photoactivation, particularly in allylic alcohol functionalization and BH amine alkylation. Mechanistic studies revealed that the diminished reactivity stemmed from light-induced demetallation of the L² and L³-based complexes, contrasting with the stability of their L¹-based counterparts. Adding exogenous ligands like PPh₃ mitigated this demetallation, explaining the catalytic activity of L² and L³ based complexes. The findings highlight the interplay of ligand design, light activation, and catalytic performance, providing a basis for advancing sustainable photocatalysis.