关键词: 受限路易斯酸碱对, 三(五氟苯基)硼, 有机胺盐酸盐, 硅烷, 硼氢化胺盐

In modern practice, frustrated Lewis pairs (FLPs) are well-known to exhibit unique chemical properties in respect to H₂ activation. Additionally, CO₂ catalytic reduction and related catalytic hydrogenations of unsaturated bonds have also been widely concerned. This paper describes designation and studies of a novel FLP catalyst system, in which the Lewis base component is introduced as an amine hydrochloride (not a free amine), while the Lewis acid component is retained [tris(pentafluorophenyl)borane, B(C₆F₅)₃ (BCF)]. With a hydridosilane as a source of the hydride, this novel system, at first, presents a new facile synthetic approach to ammonium hydridoborates [R₃NH]⁺[HBCF]^-. Remarkably, that irrespective of the bulkiness of the ammonium component, various primary, secondary and tertiary ammonium salts with HBCF^- anion can all be prepared by the suggested procedure under mild conditions and in high yields. At the same time this system may serve as a powerful tool for selective and exhaustive reduction of organic carbonyl compounds and even CO₂ down to alkanes and methane, respectively. Comparison of the ¹H NMR spectra of the starting hydrochlorides, the intermediate ammonium chloroborates [R₃NH]⁺[ClBCF]^-, and [R₃NH]⁺[HBCF]^- reveals that the appearance of the NH signals is strongly dependent upon the nature of the counterion. While in the parent chlorides signals of these protons are observed as broad singlets or multiplets due to the quadrupolar relaxation on the adjacent ¹⁴N nucleus, in the spectra of their [HBCF]^- analogues these signals exhibit distinct fine structure due to the spin-spin coupling with the ¹⁴N [¹J(¹⁴N-H)≈50 Hz; 1︰1︰1 triplets]. The latter is indicative of the increase of the symmetry of the electric field at the ¹⁴N nucleus location along with the decrease of the degree of ammonium/anoin interaction. The chemical reactivity of these [HBCF]^- analogues is interesting matched with their NH signals．

Key words: frustrated Lewis pairs, tris(pentafluorophenyl)boron, ammonium chlorides, silanes, ammonium hydridoborates