Thediscoveryofsustainable and scalablesynthetic protocols leading to gold-arylcompounds bearing N-heterocyclic carbene (NHC) ligandss parkeda ni nvestigationo f their reactivitya nd potential utility as organometallic synthons. The use of am ild base andg reen solvents provide access to these compounds, startingf rom widely available boronic acids and various [Au(NHC)Cl] complexes, with reactions taking place under air,a tr oom temperature and lead-ing to high yields with unprecedented ease. One compound, (N,N'-bis[2,6-(di-isopropyl)phenyl]imidazol-2-ylidene)(4-methoxyphenyl)gold, ([Au(IPr)(4-MeOC 6 H 4 )]), was synthesized on am ultigrams cale and used to gauge the reactivity of this class of compounds towards CÀH/NÀHb onds and with various acids, revealings imple pathways to gold-based species that possess attractive properties as materials, reagents and/ or catalysts.
Results and DiscussionOur initial approachq uestioned whether the transmetallation reaction between [Au(IPr)Cl] (1)a nd an equimolar amount of phenylboronic acid was feasible in technical grade acetonei n the presence of K 2 CO 3 (entry 1, Ta ble 1). This initial hypothesis is based on our recent work using aw eak inorganic base to [a] N.
A straightforward synthetic protocol leading to carbene-metal-amido (CMA) complexes (metal = Au, Cu) using a mild base and an environmentally desirable solvent (EtOH) has been explored, with a focus on complexes bearing backbone-substituted N-heterocyclic carbene (NHC) ligands, including BIAN-NHCs (BIAN = bis(imino)acenaphthene). The novel CMAs were structurally characterized, and gold-based CMAs bearing diverse NHCs were screened as simple, Brønsted-basic precatalysts. The readily accessible complexes display high catalytic activity in the intermolecular and intramolecular hydrocarboxylation of internal alkynes and alkynoic acids respectively, while the screening reveals the ancillary ligand effect of NHCs in these catalytic systems.[a] I.
The development of efficient and operationally simple synthetic routes to dinuclear gold(I)-amido complexes bearing aromatic/aliphatic-bridges are reported. This family of complexes was prepared utilizing environmentally friendly and sustainable reagents under...
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