title: Dicopper Cu(I)Cu(I) and Cu(I)Cu(II) Complexes in Copper-Catalyzed Azide-Alkyne Cycloaddition.
abstract: A discrete, dicopper μ-alkynyl complex, [Cu2(μ-η1:η1-C≡C(C6H4)CH3)DPFN]NTf2(DPFN = 2,7-bis(fluoro-di(2-pyridyl)methyl)-1,8-naphthyridine; NTf2-= N(SO2CF3)2-), reacts with p-tolylazide to yield a dicopper complex with a symmetrically bridging 1,2,3-triazolide, [Cu2(μ-η1:η1-(1,4-bis(4-tolyl)-1,2,3-triazolide))DPFN]NTf2. This transformation exhibits bimolecular reaction kinetics and represents a key step in a proposed, bimetallic mechanism for copper-catalyzed azide-alkyne cycloaddition (CuAAC). The μ-alkynyl and μ-triazolide complexes undergo reversible redox events (by cyclic voltammetry), suggesting that a cycloaddition pathway involving mixed-valence dicopper species might also be possible. Synthesis and characterization of the mixed-valence μ-alkynyl dicopper complex, [Cu2(μ-η1:η1-C≡C(C6H4)CH3)DPFN](NTf2)2, revealed an electronic structure with an unexpected partially delocalized spin, as evidenced by electron paramagnetic resonance spectroscopy. Studies of the mixed-valence μ-alkynyl complex's reactivity suggest that a mixed-valence pathway is less likely than one involving intermediates with only copper(I).
authors.affiliation: Department of Chemistry, University of California , Berkeley, California 94720-1460, United States.|Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Micah S
authors.identifier: 0000-0002-8549-506X
authors.initials: MS
authors.lastname: Ziegler
authors.affiliation: Department of Chemistry and Chemical Biology and The Baruch '60 Center for Biochemical Solar Energy Research, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: K V
authors.initials: KV
authors.lastname: Lakshmi
authors.affiliation: Department of Chemistry, University of California , Berkeley, California 94720-1460, United States.|Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: T Don
authors.initials: TD
authors.lastname: Tilley
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D001386:Azides / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D061565:Cycloaddition Reaction; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*
chemical_list: D000480:Alkynes; D001386:Azides; D009942:Organometallic Compounds; D003300:Copper