Role of Organic Fluoride Salts in Stabilizing Niobium Oxo-Clusters Catalyzing Epoxidation

Qingqing Zhou; Beibei Xu; Xuan Tang; Sheng Dai; Bingjie Ding; Difan Li; Anna Zheng; Tong Zhang; Yefeng Yao; Xueqing Gong; Zhenshan Hou

doi:10.1021/acs.langmuir.1c00893

Role of Organic Fluoride Salts in Stabilizing Niobium Oxo-Clusters Catalyzing Epoxidation

Langmuir. 2021 Jul 13;37(27):8190-8203. doi: 10.1021/acs.langmuir.1c00893. Epub 2021 Jun 29.

Authors

Qingqing Zhou¹, Beibei Xu², Xuan Tang¹, Sheng Dai³, Bingjie Ding¹, Difan Li¹, Anna Zheng¹, Tong Zhang¹, Yefeng Yao², Xueqing Gong¹, Zhenshan Hou^{1

4}

Affiliations

¹ Key Laboratory for Advanced Materials, Research Institute of Industrial Catalysis, East China University of Science and Technology, Shanghai 200237, China.
² Physics Department and Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062, China.
³ Key Laboratory for Advanced Materials and Feringa Nobel Prize Scientist Joint Research Center, Institute of Fine Chemicals, School of Chemistry & Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China.
⁴ Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China.

PMID: 34184530
DOI: 10.1021/acs.langmuir.1c00893

Abstract

We present here that easily available organic salts can stabilize/modify niobium (Nb) oxo-clusters. The as-synthesized Nb oxo-clusters have been characterized by various methods. These Nb oxo-clusters were catalytically active for the epoxidation of allylic alcohols and olefins with H₂O₂ as an oxidant. Notably, Nb-OC@TBAF-0.5 appeared as highly dispersed nanosized particles and showed the highest catalytic activity, which can be attributed to the following reasons on the basis of characterization. First, the strong coordination of fluorine ions with Nb sites and the steric protection with bulky organic cations led to high stabilization and dispersion of the oxo-clusters in the course of the reaction. Second, a hydrogen-bond interaction between the coordinated fluorine atom and the -OH group of allylic alcohol favored the epoxidation reaction. Third, the electron density of Nb sites decreased due to the strong electron-withdrawing ability of F^- adjacent to Nb sites, thus promoting the electrophilic oxygen transfer to the C═C bond.