School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia.
Dalton Trans. 2021 Mar 21;50(11):3931-3942. doi: 10.1039/d0dt03736b. Epub 2021 Feb 26.
The coordination chemistry of N-functionalised cyclam ligands has a rich history, yet cyclam derivatives with pendant alkynes are largely unexplored. This is despite the significant potential and burgeoning application of N-propargyl cyclams and related compounds in the creation of diversely functionalised cyclam derivatives via copper-catalysed azide-alkyne 'click' reactions. Herein we describe single crystal X-ray diffraction and spectroscopic investigations of the coordination chemistry of copper(ii) complexes of cyclam derivatives with between 1 and 4 pendant alkynes. The crystal structures of these copper complexes unexpectedly reveal a range of coordination modes, and the surprising occurrence of five unique complexes within a single recrystallisation of the tetra-N-propargyl cyclam ligand. One of these species exhibits weak intramolecular copper-alkyne coordination, and another is formed by a surprising intramolecular copper-mediated hydroalkoxylation reaction with the solvent methanol, transforming one of the pendant alkynes to an enol ether. Multiple functionalisation of the tetra-N-propargyl ligand is demonstrated via a 'tetra-click' reaction with benzyl azide, and the copper-binding behaviour of the resulting tetra-triazole ligand is characterised spectroscopically.
N-官能化环戊烷配体的配位化学有着丰富的历史，但带有末端炔烃的环戊烷衍生物在很大程度上尚未得到探索。尽管 N-丙炔基环戊烷和相关化合物在通过铜催化的叠氮化物-炔烃“点击”反应来合成各种官能化的环戊烷衍生物方面具有重要的潜力和新兴的应用，但这种情况仍然存在。在此，我们描述了具有 1 至 4 个末端炔烃的环戊烷衍生物的铜(ii)配合物的配位化学的单晶 X 射线衍射和光谱研究。这些铜配合物的晶体结构出人意料地揭示了一系列配位模式，并且在单一的四-N-丙炔基环戊烷配体的重结晶中出现了五种独特的配合物。其中一种物种表现出弱的分子内铜-炔烃配位，另一种是通过甲醇溶剂中令人惊讶的分子内铜介导的氢烷氧基化反应形成的，将一个末端炔烃转化为烯醇醚。通过与苄基叠氮化物的“四点击”反应证明了四-N-丙炔基配体的多重官能化，并且通过光谱学方法表征了所得的四三唑配体的铜结合行为。
