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

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journal contribution
posted on 16.08.2018, 00:00 by Vaishnavi Somasundaram, Praveen N. Gunawardene, Alexander M. Polgar, Mark S. Workentin, John F. Corrigan
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.

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