Reactivity of Frustrated Lewis Pair: Carbocation versus Radical Intermediates

• Published in: Chemistry : a European journal Vol. 30; no. 11; pp. e202303901 - n/a
• Main Authors: Qu, Zheng‐Wang, Zhu, Hui, Grimme, Stefan
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 21.02.2024
• Subjects: carbocation; Cations; Coupling; DFT calculations; Electron transfer; FLP; Intermediates; Phosphine; Phosphines; radical; reaction mechanism; Reagents; Styrene; Styrenes; Substrates; carbocation; FLP; radical; reaction mechanism; DFT calculations
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.202303901

Recent reports of radical formation within frustrated Lewis pairs (FLPs) suggested that single‐electron transfer (SET) could play an important role in their chemistry especially for C−C coupling. In sharp contrast, our extensive dispersion‐corrected DFT calculations show that although reactive benzhydryl radical along with phosphine radical cation species can be kinetically generated from bulky phosphines and benzhydryl cation, direct P−C hetero‐coupling may lead to bulky phosphonium cation as reactive carbocation transfer reagents to styrene substrates, which is kinetically much more favorable than the recently proposed radical C−C coupling between benzhydryl radical and styrene. Similarly, meta‐stable radical cation Mes3P+⋅ salt is also kinetically accessible via SET reactions of Mes3P and B(C6F5)3 with 0.5 equivalent of p‐O2C6Cl4. Extensive DFT calculations show that both radical HCAr2⋅ and carbocation HCAr2+ are thermally accessible from the bulky phosphonium Mes3P−CHAr2+, which are further kinetically favored by HCAr2⋅ radical self‐dimerization and by nucleophilic alkene trapping, respectively.