title: Copper and silver complexes of tris(triazole)amine and tris(benzimidazole)amine ligands: evidence that catalysis of an azide-alkyne cycloaddition ("click") reaction by a silver tris(triazole)amine complex arises from copper impurities.
abstract: The synthesis and characterization of a silver complex of the tripodal triazole ligand, tris(benzyltriazolylmethyl)amine (TBTA, L(1)), that is used as promoter to enhance Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions is reported. X-ray analysis of the silver(I) complex with L(1) reveals a dinuclear cation, [Ag2(L(1))2](2+), that is essentially isostructural to the copper(I) analogue. While the [Ag2(L(1))2](BF4)2 complex provides catalysis for the azide-alkyne cycloaddition process, evidence is presented that this arises from trace copper contamination. The synthesis of silver(I), copper(II), and copper(I) complexes of a second tripodal ligand, tris(2-benzimidazolymethyl)amine (L(2)), which is used to enhance the rate of CuAAC reactions, is also reported. X-ray crystallography of the Cu(I) complex [Cu(I)3(L(2))2(CH3CN)2](BF4)3 offers structural insight into previous mechanistic speculation about the role of this ligand in the CuAAC reaction.
authors.affiliation: School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , Parkville 3010, Victoria, Australia.
authors.forename: Timothy U
authors.initials: TU
authors.lastname: Connell
authors.forename: Christine
authors.initials: C
authors.lastname: Schieber
authors.forename: Ilaria Proietti
authors.initials: IP
authors.lastname: Silvestri
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: White
authors.forename: Spencer J
authors.initials: SJ
authors.lastname: Williams
authors.forename: Paul S
authors.initials: PS
authors.lastname: Donnelly