NHC Ligated Group 11 Metal-Arylthiolates Containing an Azide Functionality Amenable to "Click" Reaction Chemistry

The reaction of N-heterocyclic carbene (NHC) Group 11 metal complexes, [(NHC)M-X] (X = chloride, acetate), with the new azide-modified arylthiol 1-HSCH₂-2,5-Me₂-4-N₃CH₂-C₆H₂, 1 (for M = Au; X = Cl), or 1-Me₃SiSCH₂-2,5-Me₂-4-N₃CH₂-C₆H₂, 2 (for M = Cu, X = Cl; M = Ag, X = OAc), affords the "clickable" NHC-metal thiolates [( ⁱPr₂-bimy)Au-(1-SCH₂-2,5-Me₂-4-N₃CH₂-C₆H₂)], 5; [(IPr)Au-(1-SCH₂-2,5-Me₂-4-N₃CH₂-C₆H₂)], 6; [(IPr)Ag-(1-SCH₂-2,5-Me₂-4-N₃CH₂-C₆H₂)], 7; and [(IPr)Cu-(1-SCH₂-2,5-Me₂-4-N₃CH₂-C₆H₂)], 8 ( ⁱPr₂-bimy = 1,3-di-isopropylbenzimidazol-2-ylidene, IPr = 1,3-bis(2,6-di-iso-propylphenyl)imidazol-2-ylidene). Single-crystal X-ray analysis of all metal complexes show that they are two-coordinate, nearly linear, with a terminally bonded thiolate ligand possessing an accessible azide (-N₃) moiety. The strain-promoted alkyne-azide cycloaddition (SPAAC) reaction of complex 6 with bicyclo[6.1.0]non-4-yn-9-ylmethanol (BCN-OH) and dibenzocyclooctyne-amine (DBCO-NH₂) illustrated the reactivity of the azide moiety toward strain-promoted cycloaddition. The rate of the SPAAC reaction between complex 6 and BCN-OH was determined via ¹H NMR spectroscopy under second order conditions, and was compared to that of BCN-OH with PhCH₂N₃.