Synthesis and characterization of partially substituted NHC supported alane adducts using triflate or chloride salts

Abstract

Use of an aldiminium-based triflate salt as group transfer reagent to an N-heterocyclic carbene (NHC) adduct with alane [(IPr)AlH3] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene) led to the substitution of a hydride by triflate and subsequently to the formation of [(IPr)AlH2OTf] (1), which is the first structurally characterized aluminum dihydride triflate compound and the first (trifluoromethanesulfonyl)oxyalane NHC adduct. The related reaction with aldiminium-based chloride salt resulted in similar substitution and formation of mixed products [(IPr)AlH2Cl] and [(IPr)AlHCl2], which co-crystallized in the form of [(IPr)AlH3−xClx], x = 1, 2 (2). This proves that aldiminium-based salts are suitable reagents in alane chemistry. In addition, the adduct [(IPr)AlCl3] (4) was also prepared from AlCl3 and IPr carbene.