Acid–Base Interactions in Halobenzene–Ceria Systems: Insights into Oxidative Addition from Theory

Abstract

Selection of a suitable catalyst–halobenzene pair to carry out C–C coupling reactions of pharmaceutical importance has always been a challenge. CeO2-based catalysts due to the presence of alternate Lewis acid–Lewis base sites have potential for catalyzing C–C coupling reactions in which oxidative addition is an important step, as is also evident from recent reports. Analysis of adsorption and oxidative addition of halobenzenes over CeO2 requires attention, insights into which have been developed in detail in this study. Density functional theory calculations were carried out on a periodic slab of CeO2 (111) with cationic and anionic surface defects. The role of surface defects of both types on adsorption of halobenzenes was studied. The synergistic effect of the presence of cationic substitution and anionic vacancies was observed to contribute to an increase in Lewis acid–base interactions resulting in improved adsorption characteristics. Dissociation of halobenzenes was studied over the most efficient Ce1–x Pd x O2−δ catalyst established in this study. The study provides details of various surface interactions of halobenzenes with CeO2-based systems.

CO Oxidation over Ce1–xPdxO2−δ Takes Place via Vacancy Hopping

“…C of CO adsorbed at the atop site of Pd (PCV t ) with a distance of 1.89 Å. In the case of PCV t , Pd moved to the subsurface from the above atomic layer. , In the case of PCV t , two nearer oxygens from Pd atom moved away with a distance of Pd–O as 3.11 Å.…”

“…In the case of PCV t , Pd moved to the subsurface from the above atomic layer. 65,66 In the case of PCV t , two nearer oxygens from Pd atom moved away with a distance of Pd−O as 3.11 Å. Adsorption energy of CO in PCV t site was −25.88 kcal/mol, and for PCV v it was −12.97 kcal/mol. Hence, atop site PCV t offered the stronger adsorption (−25.88 kcal/mol) when compared to the other site.…”