Bond Strength and Reactivity Scales for Lewis Superacid Adducts: A Comparative Study with In(OTf)3 and Al(OTf)3. 
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)3 or In(OTf)3 with 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)3 was found to bind stronger to amides than In(OTf)3 and to provide the most reactive adducts.