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

Abstract

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, the work aimed 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 analogs 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 L1-based counterparts. Adding exogenous ligands like PPh3 mitigated this demetallation, explaining the reminiscence of catalytic activity in 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.