Solid state frustrated Lewis pair chemistry

Abstract

In solution the PCy3/B(C6F5)3 pair is rapidly deactivated by nucleophilic aromatic substitution. In the solid state (or in a fluorous liquid), however, it serves as an active frustrated Lewis pair to effectively split dihydrogen.

Dihydrogen Splitting by Intramolecular Borane‐Phosphane Frustrated Lewis Pairs: A Comprehensive Characterization Strategy Using Solid State NMR and DFT Calculations

“…However, in the absence of ultrafast MAS facilities, a more effective approach is to acquire heteronuclear correlation (HETCOR) NMR spectra under conditions where only those 1 H nuclei are detected that are most strongly dipolar‐coupled to one of the two Lewis centers. As previously discussed for an intermolecular hydrogenated B/P FLP system, this selectivity can be achieved by choosing a sufficiently short contact time (0.2–0.5 ms) for the CP step between 1 H and 11 B. Accordingly, Figures a and b show the 11 B{ 1 H} CP/HETCOR NMR spectra for compounds 3‐H 2 and 4‐H 2 , respectively.…”

“…As we have shown recently for an intermolecular borane‐phosphane FLP system, the hydrogen splitting reaction can also be conducted directly in the solid state and monitored ex‐situ by NMR methods . In the present contribution, we report results of an in‐depth structural characterization of four intramolecular borane‐phosphane FLP hydrogenation products (see Scheme ) using solid‐state NMR and DFT calculations.…”

“…During the past decade frustrated Lewis pairs (FLPs) have gained great attention as versatile metal‐free cooperative catalytic systems for a large number of important chemical transformations . FLPs are chemical systems containing a Lewis base as well as a Lewis acid moiety in close proximity, where sterically demanding substituents at both Lewis centers prevent “quenching”, i. e ., the formation of a chemical bond.…”

Solid‐State Nuclear Magnetic Resonance Techniques for the Structural Characterization of Geminal Alane‐Phosphane Frustrated Lewis Pairs and Secondary Adducts

“…During the past decade, frustrated lewis pairs (FLPs) have gained considerable attention as versatile metal‐free reagents applicable in various important chemical processes such as adduct formation, activation, or cooperative catalytic transformations. [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ] FLPs are chemical systems containing a lewis base as well as a lewis acid moiety in close proximity, where the formation of a chemical bond (“quenching”) is not a thermodynamic sink as a result of the presence of sterically demanding substituents at the Lewis centers. Such “frustration” bestows important catalytic properties on these molecules, resulting from the cooperative action of the lewis centers upon the substrate molecule.…”

Characterization of H2‐Splitting Products of Frustrated Lewis Pairs: Benefit of Fast Magic‐Angle Spinning

“…Instead, highly reactive species are obtained capable of undergoing a variety of reactions, e. g. small molecule activation such as di‐hydrogen . These compounds split di‐hydrogen heterolytically, a concept which has recently been extended also to solid‐state reactions ,. Solid‐state NMR has been applied extensively to structurally characterize FLP‐based systems …”