Design and Construction of Novel Frustrated Lewis Pairs Based on Modified Lewis Acid B(C6F5)3

This study aims to systematically investigate the influence of substituent effects on the strength of Lewis acid–base interactions in frustrated Lewis pairs (FLPs). Specifically, -C6F5 groups of the classical Lewis acid B(C6F5)3 are sequentially replaced with -C6Cl5, -C6Br5, and -C6I5 groups, and the Lewis acids are paired with the Lewis base 1,3-disubstituted imidazol-2-ylidene (ItBu) to form FLPs. Further energy decomposition analysis (sobEDA), orbital analysis, and molecular fragment density difference (MFDD) analysis reveal the nature of the substituent effect on the interaction energy (∆Eint) of the FLPs. The research findings indicate that the ∆Eint of B(C6F5)3-ItBu, B(C6F5)x(C6Y5)3−x-ItBu (x = 0, 1, 2; Y = Cl, Br, I) originates mainly from the interaction between the outermost halogen atom of the Lewis acid and the central carbon (C) atom of the Lewis base, rather than from the interaction between the central atoms boron (B) and carbon (C). This mechanism ultimately leads to a ∆Eint for B(C6F5)2(C6Y5)-ItBu (Y = Cl, Br, I) that is comparable to that of B(C6F5)3-ItBu. This indicates that modified B(C6F5)2(C6Y5) (Y = Cl, Br, I) exhibits greater potential for the construction of novel FLPs.