Department of Chemistry, University of California , Berkeley, California 94720-1460, United States.
Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
J Am Chem Soc. 2017 Apr 19;139(15):5378-5386. doi: 10.1021/jacs.6b13261. Epub 2017 Apr 10.
A discrete, dicopper μ-alkynyl complex, [Cu(μ-η:η-C≡C(CH)CH)DPFN]NTf (DPFN = 2,7-bis(fluoro-di(2-pyridyl)methyl)-1,8-naphthyridine; NTf = N(SOCF)), reacts with p-tolylazide to yield a dicopper complex with a symmetrically bridging 1,2,3-triazolide, [Cu(μ-η:η-(1,4-bis(4-tolyl)-1,2,3-triazolide))DPFN]NTf. 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, Cu(μ-η:η-C≡C(CH)CH)DPFN, 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).
一个离散的、双核μ-炔基配合物，[Cu(μ-η:η-C≡C(CH)CH)DPFN]NTf（DPFN=2,7-双（氟二（2-吡啶基）甲基）-1,8-萘啶；NTf= N(SOCF)），与对甲苯叠氮反应生成一个具有对称桥接的 1,2,3-三唑化物的双核铜配合物，[Cu(μ-η:η-(1,4-双（4-甲苯基）-1,2,3-三唑化物))DPFN]NTf。这种转化表现出双分子反应动力学，代表了铜催化叠氮-炔环加成（CuAAC）的双金属机理的一个关键步骤。μ-炔基和μ-三唑化物配合物经历可逆的氧化还原事件（通过循环伏安法），表明涉及混合价双核铜物种的环加成途径也可能是可行的。混合价μ-炔基双核铜配合物，Cu(μ-η:η-C≡C(CH)CH)DPFN的合成和表征揭示了一种具有出乎意料的部分离域自旋的电子结构，这一点通过电子顺磁共振波谱得到了证明。对混合价μ-炔基配合物反应性的研究表明，混合价途径不太可能涉及仅含有铜（I）的中间体。
