Design and reactions of a carbon Lewis base/boron Lewis acid frustrated Lewis pair

Abstract

The conjugated dienamine selectively adds Piers' borane [HB(CF)] to give the enamine/borane system , which features a boratirane structure by internal enamine carbon Lewis base to boron Lewis acid interaction. Compound behaves as a C/B frustrated Lewis pair and undergoes typical addition reactions to benzaldehyde, several nitriles and to sulfur dioxide.This article is part of the themed issue 'Frustrated Lewis pair chemistry'.

Frustrated Lewis pair chemistry

“…We begin with a conceptual consideration of the broader context of FLP chemistry by Fontaine & Stephan [1] and then Bullock & Chambers [2] provide an overview of the notion of FLP chemistry across the periodic table. Grimme and co-workers [3] provide a discussion of the theoretical considerations of the quintessential reaction of FLPs, the activation of H 2 , while Erker and co-workers [4] report on the development of FLPs derived from carbon-Lewis bases and boron-Lewis acids. Melen and co-workers [5] discuss reactions of FLPs inspired by biologically relevant systems and Uhl and co-workers [6] describe aluminiumphosphorus based FLPs.…”

Activation of SO2 by N/Si+ and N/B Frustrated Lewis Pairs: Experimental and Theoretical Comparison with CO2 Activation

“…The reaction mixture was exposed to aC O 2 atmosphere (1 bar). Aw hite precipitate was formed and complex 7 BCy2 identified by 1 H, 13 ), 49.12 (CH 2 TBD), 48.83 (CH 2 TBD), 41.77 (CH 2 TBD), 41.57 (CH 2 TBD), 30. 22, 29.74, 29.57, 29.29, 28.85 (CH 2 Cy), 27.56 (CH Cy), 21.89 (CH 2 TBD), 21.43 ppm (CH 2 TBD); TBD-BCy 2 -SO 2 (8 BCy2 ):A no ven-dried J.…”

“…Under argon, B-Iodo-9-BBN (62 mL, 1 m solution in hexanes, 0.062 mmol, 1equiv) was added and the reaction mixture was stirred for 1hat room temperature. Complex 8 BBN was obtained in approximately 80 %y ield and identified by 1 H, 13…”

“…Exposing aT HF solution of TBD-SiMe 2 Cl (3[Cl]) to 2equiv of SO 2 did not change the color of the solution, butf ormation of an ew single species 5[Cl] was evidenced from the 1 Ha nd 13 CNMR spectra of the crude mixture. This compound could not be isolated, because the fixation of SO 2 was reversible and SO 2 was rapidly released duringe vaporation of the solvent or when the solution was purged with argon.…”

“…The activation of SO 2 with FLPs has been scarcely studied and only a few examples of isolated adducts have been reported . Examples mostly include systems containing a boron center as the acidic site and a phosphorus center as the basic site (B/P), even though B/C, M/P (with M=Zr or Hf), and Si/P combinations were also reported (Figure ). Although a wealth of knowledge exists regarding complexes of SO 2 with amines, no FLP involving an amine as a Lewis base has been reported to form an adduct with SO 2 .…”