title: Bond Strength and Reactivity Scales for Lewis Superacid Adducts: A Comparative Study with In(OTf)3and Al(OTf)3.
abstract: Metal triflates, often called Lewis superacids, are potent catalysts for organic synthesis. However, the reactivity of a given Lewis superacid toward a given base is difficult to anticipate. A systematic screening of catalysts is often necessary when developing synthetic methodologies. Presented herein is the development of quantitative reactivity and bond strength scales by using mass spectrometry (MS). By applying a collision-induced dissociation (CID) technique to the adducts formed between Lewis superacids Al(OTf)3or In(OTf)3with a series of amides bases, including monodentate and bidentate ligands, different dissociation pathways were observed. Quantitative relative energy scales were established by performing energy-resolved mass spectrometry (ERMS) analysis on the adducts. ERMS of the adducts affords a bond strength scale when the fragmentation leads to the loss of a ligand, and reactivity scales when the dissociation leads to the C-F bond activation of one triflate anion or the deprotonation of the ligand. Al(OTf)3was found to bind stronger to amides than In(OTf)3and to provide the most reactive adducts.
authors.affiliation: Institut de Chimie de Nice, UMR 7272, Université Côte D'Azur, CNRS, 06108, Nice, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Compain
authors.affiliation: Institut de Chimie de Nice, UMR 7272, Université Côte D'Azur, CNRS, 06108, Nice, France.
authors.forename: Lauri
authors.initials: L
authors.lastname: Sikk
authors.affiliation: Institut de Chimie de Nice, UMR 7272, Université Côte D'Azur, CNRS, 06108, Nice, France.
authors.forename: Lionel
authors.initials: L
authors.lastname: Massi
authors.affiliation: Institut de Chimie de Nice, UMR 7272, Université Côte D'Azur, CNRS, 06108, Nice, France.
authors.forename: Jean-François
authors.identifier: http://orcid.org/0000-0002-5500-5461
authors.initials: JF
authors.lastname: Gal
authors.affiliation: Institut de Chimie de Nice, UMR 7272, Université Côte D'Azur, CNRS, 06108, Nice, France.
authors.forename: Elisabet
authors.initials: E
authors.lastname: Duñach
keywords: Lewis superacids; amide bases; bond strength scale; collision-induced dissociation; reactivity scale