Issue 11, 2021

Copper(ii) complexes of N-propargyl cyclam ligands reveal a range of coordination modes and colours, and unexpected reactivity

Abstract

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.

Graphical abstract: Copper(ii) complexes of N-propargyl cyclam ligands reveal a range of coordination modes and colours, and unexpected reactivity

Supplementary files

Article information

Article type
Paper
Submitted
30 oct. 2020
Accepted
21 janv. 2021
First published
08 févr. 2021

Dalton Trans., 2021,50, 3931-3942

Copper(II) complexes of N-propargyl cyclam ligands reveal a range of coordination modes and colours, and unexpected reactivity

A. J. Counsell, M. Yu, M. Shi, A. T. Jones, J. M. Batten, P. Turner, M. H. Todd and P. J. Rutledge, Dalton Trans., 2021, 50, 3931 DOI: 10.1039/D0DT03736B

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