Copper-Catalyzed Huisgen [3 + 2] Cycloaddition of Gold(I) Alkynyls with Benzyl Azide. Syntheses, Structures, and Optical Properties

The copper(I)-catalyzed Huisgen [3 + 2] cycloaddition is a general reaction encompassing wide ranges of organoazide and primarily terminal alkyne reacting partners. Strained internal alkynes can also undergo cycloaddition with azides. We report here that tetrakis(acetonitrile)copper(I) hexafluorophosphate catalyzes the [3 + 2] cycloaddition of (phosphine)- and (N-heterocyclic carbene)gold(I) alkynyls with benzyl azide. Isolated yields of up to 96% result. The reaction protocol broadly tolerates functionalities on the alkynyl reagent. Gold(I) triazolate products form with complete 1,4-regioselectivity. Some 15 new gold(I) triazolates are reported along with crystal structures of nine. Triazolate complexes bearing polycyclic aromatic substituents show dual singlet- and triplet-state luminescence from excited states localized on the aromatic fragment. Time-resolved emission experiments find long lifetimes consistent with triplet emission parentage. Absorption and emission transitions are analyzed with time-d...