Copper(I) and Silver(I) Bis(trifluoromethanesulfonyl)imide and Their Interaction with an Arene, Diverse Olefins, and an NTf2--Based Ionic Liquid

The chemistry of coinage metal bis(triflyl)imides of technological interest, CuNTf2 and AgNTf2, their synthesis and complexes with excess of comparatively weakly coordinating NTf2- as well as with ether, olefins, and the arene mesitylene are described. The existence of the solvent-free pure phase [CuNTf2]8 has not been evidenced so far. Contrary to the literature, in which the preparation of [CuNTf2]8 is supposed to be carried out by reacting mesityl copper, [Cu(Mes)]5, and HNTf2, we found that in fact this reaction leads reproducibly to the interesting copper diarene sandwich complex [Cu(?3-MesH)2][Cu(NTf2)2] (1) (MesH=1,3,5-trimethylbenzene). The unexpectedly stable molecular etherate [Cu(Et2O)(NTf2)] (2) turned out to be the best precursor for CuNTf2 having only an inert and easily exchangeable solvent ligand. The coordination mode of NTf2- in 1 and 2 as well as in the hitherto unknown crystalline phase of [AgNTf2]8 (3) is described. The complex formation, which takes place when dissolving 2 or 3 in the room temperature ionic liquid (RTIL) [emim]NTf2 ([emim]+=1-ethyl-3-methylimidazolium), has been studied. Furthermore, the reaction of 13 towards the diolefins 1,5-cyclooctadiene (COD), 2,5-norbornadiene (NBD) and isoprene (2-methylbuta-1,3-diene) and towards ethylene has been investigated. The products 413 of these conversions have been isolated and fully characterized by NMR- and IR spectroscopies, mass spectrometry, and elemental- and XRD analyses. The potential of [Cu(?3-MesH)2][Cu(NTf2)2] (1), [Cu(Et2O)(NTf2)] (2) and [AgNTf2]8 (3) as well as of [emim][M(NTf2)2] (M=Cu 4, Ag 5) as chemisorbers for ethylene was studied by NMR spectroscopy.