An easy-to-perform evaluation of steric properties of Lewis acids

Abstract

Steric and electronic effects play a very important role in chemistry, as these effects influence the shape and reactivity of molecules. Herein, an easy-to-perform approach to assess and quantify steric...

Anionic N-heterocyclic carbenes featuring weakly coordinating perfluoroalkylphosphorane moieties

“…The optimized (DFT) structure of the Se adduct of 4 shows that both P–N–C2 units would be strongly bent (∡(P–N–C2) = 133.4°) compared to 4 (∡(P–N–C2) = 124.7(2) and 125.1(2)°). The LAB-Rep model 69 for the analysis of Lewis acid/base adduct formation also shows that the Se adduct of 4 is sterically very encumbered (% V bur_all of 101.0%; for details see the ESI†) and hence, its formation is unfavored.…”

“…64 The large number of chemically stable tris( pentafluoroethyl)difluorophosphorane derivatives of the general formula (C 2 F 5 ) 3 PF 2 R (R = NHC, 65 amine, 66 DMAP 67 (DMAP = 4-(dimethylamino)pyridine), …) underlines the ability to form stable Lewis acid/base pairs. 68 Herein, we describe the synthesis of mono-and dianioic tris( pentafluoroethyl)difluorophosphorane-functionalized WCA-NHCs with the highly sterically demanding (C 2 F 5 ) 3 PF 2 Lewis acid 69 attached to the N imidazole atom(s) (Fig. 1C).…”

“…Herein, we describe the synthesis of mono- and dianioic tris(pentafluoroethyl)difluorophosphorane-functionalized WCA-NHCs with the highly sterically demanding (C 2 F 5 ) 3 PF 2 Lewis acid 69 attached to the N imidazole atom(s) (Fig. 1C).…”

Examining the reactivity of tris(ortho-carboranyl)borane with Lewis bases and application in frustrated Lewis pair Si–H bond cleavage

“…Preparation of (1), 2563 (10), 2544 (9), 1475 (12), 1131 (11), 1076 (6), 1034 (3), 987 (13), 880 (5), 775 (2), 746 (14), 726 (4), 658(15); HRMS (±ESI): a peak corresponding to the adduct was not observed.…”

“…7,10 In addition to the greater Lewis acidity, the calculated steric profile of the fluoride adduct of BoCb 3 revealed greater bulk at boron than B(C 6 F 5 ) 3 with a buried volume of 71.9% compared to 58.9%. 11 With the greater bulk of BoCb 3 , a wider library of Lewis bases could be compatible for FLP chemistry which is herein investigated. In the disclosure of BoCb 3 , acetonitrile, triethylphosphine oxide, and benzaldehyde adducts were reported (Fig.…”