Cooperative activating effects of metal ion and Brønsted acid on a metal oxo species. Issue 2 (11th November 2020)

• Record Type: Journal Article
• Authors: Chen, Gui; Ma, Li; Lo, Po-Kam; Mak, Chi-Keung; Lau, Kai-Chung; Lau, Tai-Chu
• Is Part Of: Chemical science. Volume 12:Issue 2(2021)
• Page Start: 632
• Page End: 638
• Publication Date: 2020-11-11
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d0sc04069j
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Combining a weak Lewis acid and weak Brønsted acid produces strong cooperative effects for activating metal oxo species towards alkane oxidation. Abstract : Metal oxo (MO) complexes are common oxidants in chemical and biological systems. The use of Lewis acids to activate metal oxo species has attracted great interest in recent years, especially after the discovery of the CaMn4 O5 cluster in the oxygen-evolving centre of photosystem II. Strong Lewis acids such as Sc 3+ and BF3, as well as strong Brønsted acids such as H2 SO4 and CF3 SO3 H, are commonly used to activate metal oxo species. In this work, we demonstrate that relatively weak Lewis acids such as Ca 2+ and other group 2 metal ions, as well as weak Brønsted acids such as CH3 CO2 H, can readily activate the stable RuO4 − complex towards the oxidation of alkanes. Notably, the use of Ca 2+ and CH3 CO2 H together produces a remarkable cooperative effect on RuO4 −, resulting in a much more efficient oxidant. DFT calculations show that Ca 2+ and CH3 CO2 H can bind to two oxo ligands to form a chelate ring. This results in substantial lowering of the barrier for hydrogen atom abstraction from cyclohexane.