No abstract

Metal salts of triflic acid, CF 3 SO 2 OH and of triflimidic acid, [CF 3 SO 2 ] 2 NH, often called "Lewis superacids", are powerful catalysts for several classes of reactions. Typical applications developed at the Institut de Chimie de Nice during the last decade, mostly in the domain of inter-and intramolecular carbon-carbon, carbon-oxygen and carbon-sulfur bond formation, are illustrated. During the last three years, the characterization of metal triflates and triflimides by electrospray mass spectrometry was also accomplished in our Institute. Displacement of one anion of the salt by strong neutral ligands was developed as a mean for generating characteristic positive ions. In an effort toward the quantitative description of the ligand/metal bonding and the catalytic role of the Lewis acid, a ligand competition method was devised. An exploratory study attests that subtle structural effects on the donor/acceptor interaction can be evidenced using this simple mass spectrometric method. Al(OTf) 3 (5 mol%) CH 2 Cl-CH 2 Cl, reflux 30 min 83% S COOH O S O Scheme 9. Hydrocarboxylation of olefins catalyzed by Al(III) triflate SH In(OTf) 3 (5 mol%) CH 3 NO 2 , reflux 1.5 h S 91% Scheme 10. Hydrothiolation of olefins catalyzed by In(III) triflate

The interaction between two Lewis "superacid" catalysts Zn(OTf) 2 and In(OTf) 3 and series of amide and phosphate ligands is quantitatively characterized by electrospray ionization mass spectrometry (ESI-MS). A specific feature of the ESI-MS spectra of the mixture of metal triflates and Lewis bases is the formation of ionic adducts resulting from the displacement of one triflate anion by two neutral ligands. A ligand competition model is developed, which describes the relative intensities of the ionic adducts as a function of relative ligand concentrations. The relative affinities deduced from the ligand competition method are combined in an affinity scale for the metal triflate.