Frustrated Lewis pair-ligated tetrelenes

Abstract

The reactivity of [PB{SiX2}] (X = Cl, Br; PB = 1,2-iPr2C6H4BCy2; E = Si, Ge) adducts is described, with an initial focus on reduction attempts to access [PB{E}]x species; however,...

Atypical “Masked” Frustrated Lewis Pair Character in a Geminal‐Linked Phosphine‐Borane

“…[5f,8,18] However, combining 1 with H 3 N • BH 3 in benzene (Scheme 3a) gave an entirely different result. Analysis of the final product mixture by 11 B{ 1 H} NMR spectroscopy in CDCl 3 revealed a doublet resonance at À 42.3 ppm ( 1 J BP = 57.0 Hz), which further split into a multiplet pattern in the proton-coupled 11 B NMR spectrum. This peak was accompanied by a 11 B NMR singlet at 48.7 ppm, which matched the literature shift of the aminoborane H 2 NBCy 2 ; its presence was also confirmed by 1 H and 13 C{ 1 H} NMR spectroscopy.…”

“…Analysis of the final product mixture by 11 B{ 1 H} NMR spectroscopy in CDCl 3 revealed a doublet resonance at À 42.3 ppm ( 1 J BP = 57.0 Hz), which further split into a multiplet pattern in the proton-coupled 11 B NMR spectrum. This peak was accompanied by a 11 B NMR singlet at 48.7 ppm, which matched the literature shift of the aminoborane H 2 NBCy 2 ; its presence was also confirmed by 1 H and 13 C{ 1 H} NMR spectroscopy. [19] As before, a new fluorene-containing product was isolated by crystallization and shown to be the phosphine-borane complex H 3 B • i Pr 2 P(C 13 H 9 ) (4) (Scheme 3 and Figure 4a).…”

“…All carbon-bound hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and angles [°]: P1À C1 1.8739 (17), C1À B1 1.641(3), P1À B2 1.958(2); B1À P1À C1 120.60 (11).…”

“…11 B{ 1 H} NMR (159.8 MHz, CDCl 3 ): δ À 42.2 (d, J BP = 68.9 Hz, BH 3 ). 11 B NMR (159.8 MHz, CDCl 3 ): δ À 45.7 to À 38.9 (m, BH 3 ). NMR data observed for D 2 NBCy 2 : 1 H NMR (699.8 MHz, CDCl 3 ): δ 1.61-1.77 (m, 11H, CyCH 2 ), 1.34-1.16 (m, 6H, CyCH 2 ), 1.00À 1.08 (m, 3H, CyCH 2 ), 0.83-0.99 (m, 2H, CyCH).…”

“…Our first efforts in this regard involved preparing FLP ligands with increased bite angles as compared to PB, but these proved to be much less reactive due to a strong intramolecular PÀ B bonding in their uncomplexed forms. [11] Herein, we report the synthesis of a geminal-linked phosphine-borane FLP ligand, 1, (Figure 1c) with a potentially smaller bite angle. Interestingly, the reactivity of this new P/B ligand differs markedly from that of other geminal FLP systems and shows "masked" FLP behavior modulated by C(fluorene)-B bond scission.…”