Colorimetric Metal‐Free Detection of Carbon Monoxide: Reversible CO Uptake by a BNB Frustrated Lewis Pair

Abstract

We report two BNB-type frustrated Lewis pairs which feature an acceptor-donor-acceptor functionalized cavity, and which differ in the nature of the B-bound fluoroaryl group (C 6 F 5 vs. C 6 H 3 (CF 3 ) 2 -3,5, Ar f ). These receptor systems are capable of capturing gaseous CO, and in the case of the -BAr f 2 system this can be shown to occur in reversible fashion at/above room temperature. For both systems, the binding event is accompanied by migration of one of the aryl substituents to the electrophilic carbon of the CO guest. Experiments utilizing an additional equivalent of P t Bu 3 allow the initially formed (non-migrated) CO adduct to be identified and trapped (via demethylation), while also establishing the reversibility of the B-to-C migration process. When partnered with the slightly less Lewis acidic -BAr f 2 substituent, this reversibility allows for release of the captured carbon monoxide in the temperature range 40-70 8C, and the possibility for CO sensing, making use of the associated colourless to orange/ red colour change.

A deprotonation pathway to reactive [B]CH2 boraalkenes

“…The structure suggested a pathway of the formation of compound 20b that involved the intermediate generation of a boron–carbonyl, 24 potentially 18b (see Scheme 7). Reduction by the distant B–H boron hydride could have led to a formyl borane ( 19b ) 25 that then underwent a cascade of rearrangement steps: C 6 F 5 migration from boron to the adjacent formyl carbon (a principally established reaction step in borane/CO chemistry) 26 concomitant with the bulky IMes ligand exchanging positions from the B-FpXyl to the less sterically encumbered B–C 6 F 5 functionality and ring closure. Product 20b shows the pair of C 6 F 5 -substituents at boron and the ring carbon atom C5 in a 1,2- cis position.…”

Photocatalytic non-oxidative conversion of methane

“…45 In 2007, Professor Stephan proposed the concept of ''Frustrated Lewis Pairs (FLPs),'' denoting pairs of Lewis acids and bases that are prevented from interacting directly due to steric or other factors. 46 Recently, solid FLPs, composed of spatially separated Lewis acid (LA) and Lewis base (LB) sites on solid surfaces, have been demonstrated to be effective in activating molecules like H 2 , CO 2 , and CO. [47][48][49] In response to the challenge of polarizing the methane C-H bond, the Wang team utilized theoretical calculations to design a TiO 2 -based FLP with hierarchical pore structure, achieving superior C-H stretching with a high photocatalytic CH 4 conversion rate (139 mmol g À1 h À1 ). 50 Meanwhile, the Chang group explored ''Single Atom''-''Frustrated Lewis Pair'' (SA-FLP) dual active site catalysts through theoretical calculations, applying them in NOCM.…”