Efficient CO-free carbonylation of aryl halides catalyzed by SBA-15-supported Pd-1,10-phenanthroline

A robust heterogeneous palladium catalyst was constructed by immobilizing a 1,10-phenanthroline-Pd(II) complex onto mesoporous SBA-15 silica via post-synthetic surface functionalization. The catalyst, SBA-15@PHEN-Pd(II), was prepared through sequential silylation of SBA-15, covalent anchoring of 5-amino-1,10-phenanthroline, and subsequent coordination with PdCl₂. Comprehensive characterization by TGA, XPS, atomic absorption spectroscopy (AAS), and Energy-dispersive X-ray spectroscopy (EDAX) confirmed successful surface modification and palladium immobilization. XPS analysis indicated that palladium is present in the + 2 oxidation state and coordinated to the phenanthroline nitrogens. SBA-15@PHEN-Pd(II) efficiently catalyzed CO-free carbonylation of aryl halides to carboxylic acids using a formic acid/DCC system. Systematic optimization identified DMF and NaOH at 120 °C as optimal, enabling up to 76% yield across a broad substrate scope. Reactivity followed the order Ar-I > Ar-Br > Ar-Cl, and substrates bearing electron-withdrawing substituents exhibited enhanced reactivity. Negligible palladium leaching was observed, and hot filtration experiments confirmed the heterogeneous nature of the catalyst. SBA-15@PHEN-Pd(II) exhibits sustained catalytic activity over six consecutive cycles, highlighting its stability and efficiency as a CO-free carbonylation catalyst.