Tris[(trifluoromethyl)sulfonyl]methane and Related Salts

Abstract

[60805-12-1] Tf3CH (MW 412.2) InChI = 1S/C4HF9O6S3/c5-2(6,7)20(14,15)1(21(16,17)3(8,9)10)22(18,19)4(11,12)13/h1H InChIKey = MYIAPBDBTMDUDP-UHFFFAOYSA-N M = H, n = 1 [224317-58-2] (Tf3C)3Yb (MW 1406.7) (anhydrous) InChI = 1S/3C4F9O6S3.Yb/c3*5-2(6,7)20(14,15)1(21(16,17)3(8,9)10)22(18,19)4(11,12)13;/q3*-1;+3 InChIKey = GNGMSTGPEJMQKM-UHFFFAOYSA-N M = Yb, n = [224317-59-3] (Tf3C)3Sc (MW 1278.6) (anhydrous) InChI = 1S/3C4F9O6S3.Sc/c3*5-2(6,7)20(14,15)1(21(16,17)3(8,9)10)22(18,19)4(11,12)13;/q3*-1;+3 InChIKey = LRDKRKSPTYEXCA-UHFFFAOYSA-N M = Sc, n = 3 [261728-13-6] (Tf3C)2Cu (MW 886.0) InChI = 1S/2C4F9O6S3.Cu/c2*5-2(6,7)20(14,15)1(21(16,17)3(8,9)10)22(18,19)4(11,12)13;/q2*-1;+2 InChIKey = DERWDIPDZXUVNB-UHFFFAOYSA-N M = Cu, n = 2 [114395-68-5] Tf3CCs (MW 544.1) InChI = 1S/C4F9O6S3.Cs/c5-2(6,7)20(14,15)1(21(16,17)3(8,9)10)22(18,19)4(11,12)13;/q-1;+1 InChIKey = ZVPDKZBKUGXYRF-UHFFFAOYSA-N M = Cs, n = 1 [114395-71-0] Tf3CAg (MW 519.1) InChI = 1S/C4F9O6S3.Ag/c5-2(6,7)20(14,15)1(21(16,17)3(8,9)10)22(18,19)4(11,12)13;/q-1;+1 InChIKey = LNHRIDDGXXLCSC-UHFFFAOYSA-N M = Ag, n = 1 (M = H, n = 1: a Brønsted superacid, which can be transformed into recyclable, highly catalytically active metal salts) Structure: the core framework of the tris[(trifluoromethyl)sulfonyl]methide anion comprises three CS bonds, with the negative charge formally on the central carbon atom. However, the bulk negative charge is almost certainly on the (six) sulfone oxygens by resonance delocalization. The X-ray crystal structures of scandium and ytterbium triflide have seven and eight water aqua ligands respectively, (and one included water molecule each, for a total of eight and nine H2O/M), the assemblage is reinforced by hydrogen bonds between the aqua ligands, the included water molecule, and the sulfone oxygen atoms. The central carbon—which shows sp2 hybridization— is not associated with the water ensemble. For the free acid, presumably there is much dissociation and the main interaction with the proton is through the oxygen atoms. The 19F and 13C NMR spectra show only one and two resonances, respectively, demostrating rapid exchange. The same is true for the lanthanide triflides in aqueous solution where the triflide ligands are effectively dissociated. Alternate Name: M = H, n = 1: tris(triflyl)methane, triflidic acid; M = Yb, n = 3: ytterbium(III) tris[tris(trifluoromethylsulfonyl) methide], ytterbium(III) triflide; M = Sc, n = 3: scandium(III) tris[tris(trifluoromethylsulfonyl)methide], scandium(III) triflide; M = Cu, n = 2: copper(II) bis[tris(trifluoromethylsulfonyl) methide], copper(II) triflide; M = Cs, n = 1: cesium(I) tris(trifluoromethylsulfonyl)methide, cesium(I) triflide; M = Ag, n = 1: silver(I) tris(trifluoromethylsulfonyl)methide, silver(I) triflide. Solubility: M = H, n = 1: soluble in water and diethyl ether. Analysis of Reagent Purity: M = H, n = 1: titrated against a standard NaOH solution (phenolphthalein as indicator) in water immediately after sublimation. Preparative Methods: tris(trifluoromethanesulfonyl)methane (‘triflidic acid’), HCTf3, was first prepared by Turowsky and Seppelt using gaseous CF3SO2F as the electrophilic triflyl group source.1 More recently, Barrett et al. have developed a convenient synthesis from triflic anhydride.2, 3 Preparation of salts (methides or ‘triflides’) of triflidic acid have been performed by three general methods: by reaction of the free acid with a metal carbonate (K, Rb, Cs, Ag) in water (eq 1),1 the reaction of AgC(SO2CF3)3 with metal chlorides in dichloromethane (Yb, Sc, Cu) (eq 2),4 or by the action of the free acid on metal oxides in water (Yb, Sc) (eq 3).2, 3 A bismuth(III) salt has also been prepared by the action of triflidic acid on Bi(OEt)3 in diethyl ether.5 (1) (2) (3) 13C & 19F NMR Data for (Tf3C)nM M n 19F(δ/ppm) Reference 13F(δ/ppm) Reference H 1 −76.8aa CD3CN. 1 −78.4bb D2O. 5 122.6(q, J=326 Hz)b, cb D2O. c Central C(SO2CF3)3 carbon not recorded. 5 Cs 1 −76.6aa CD3CN. 2 121.7(q, J=326 Hz), 83.8aa CD3CN. 2 Yb 3 −76.5aa CD3CN. 2 122.7(q, J=326 Hz), 84.1bb D2O. 2 Sc 3 −75.9bb D2O. 2 122.6(q, J=326 Hz), 84.0bb D2O. 2 Cu 2 −12.59b, db D2O. d Referenced against CH3C6H5— all other 19F shifts against CFCl3. 4 Ag 1 No data available 1 No data available a CD3CN. b D2O. c Central C(SO2CF3)3 carbon not recorded. d Referenced against CH3C6H5— all other 19F shifts against CFCl3. Purification: M = H, n = 1: sublimation. Handling, Storage, and Precautions: M = H, n = 1: triflidic acid is a Brønsted superacid. Care should be taken in its handling. It is conveniently stored as the cesium salt (M = Cs, n = 1) which readily precipitates from water. Sublimation from concentrated sulfuric acid (CARE) liberates triflidic acid as required.