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Arylhydrazone ligands as Cu-protectors and -catalysis promoters in the azide–alkyne cycloaddition reaction

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Abstract

A series of water soluble copper(II) complexes, [Cu(κO1O2N-H2L1)(H2O)2]·2H2O (2), [Cu(κO-H3L1)2(H2O)4] (3), [Cu(κO-H4L2)2(H2O)4] (5) and [Cu(H2O)6]·2H2L3·2(CH3)2NCHO (7), were prepared by the reaction of Cu(NO3)2·3H2O with sodium (Z)-2-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)benzenesulfonate, [Na(μ4-1:2κO1,2κO2,3κO3,4κO4-H3L1)]n (1; for 2 and 3), sodium (Z)-3-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)-4-hydroxybenzene-sulfonate, [Na(μ-1κO1,2κO2-H4L2)]2 (4; for 5) or sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazineyl)naphthalene-1-sulfonate, [Na(μ-1κO1O2,2κO3-H2L3)(CH3OH)2]2 (6; for 7). Compounds 1–7 were fully characterized, also by single-crystal X-ray diffraction analysis, and applied as homogeneous catalysts for the azide–alkyne cycloaddition (AAC) reaction to afford 1,4-disubstituted 1,2,3-triazoles. A structure–catalytic activity relationship has been recognized for the first time on the basis of the occurrence of resonance- and charge-assisted hydrogen bond interactions (RAHB and CAHB), in charge and ligand binding modes, enabling the catalytic activity of the compounds to be ordered as follows: Cu(NO3)27 (complex salt with RAHB and CAHB) < 3 (with RAHB and CAHB) < 5 (with RAHB) < 2 (neither RAHB nor CAHB). Complex 2, without such non-covalent interactions, was found to be the most efficient catalyst for the AAC reaction, affording up to 98% product yield after being placed for 15 min, at 125 °C, in a water/acetonitrile mixture under low power (10 W) MW irradiation.

Graphical abstract: Arylhydrazone ligands as Cu-protectors and -catalysis promoters in the azide–alkyne cycloaddition reaction

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Publication details

The article was received on 03 Dec 2018, accepted on 04 Jan 2019 and first published on 07 Jan 2019


Article type: Paper
DOI: 10.1039/C8DT04771E
Citation: Dalton Trans., 2019, Advance Article
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    Arylhydrazone ligands as Cu-protectors and -catalysis promoters in the azide–alkyne cycloaddition reaction

    A. G. Mahmoud, M. F. C. Guedes da Silva, K. T. Mahmudov and A. J. L. Pombeiro, Dalton Trans., 2019, Advance Article , DOI: 10.1039/C8DT04771E

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