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Issue 12, 2016
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New aqua-soluble dicopper(II) aminoalcoholate cores for mild and water-assisted catalytic oxidation of alkanes

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Abstract

Two new dicopper(II) aminoalcoholate compounds, namely a discrete 0D complex [{Cu(Hdea)(H2dea)}22-H2pma)]·3H2O (1) and a 1D coordination polymer [Cu22-H2tea)22-nda)]n·2nH2O (2), were self-assembled from copper(II) nitrate, an aminoalcohol {diethanolamine (H2dea) or triethanolamine (H3tea)} and carboxylic acid {pyromellitic (H4pma) or 2,6-naphthalenedicarboxylic (H2nda)} building blocks. Both products were isolated as stable and water-soluble microcrystalline solids and fully characterized by IR spectroscopy, ESI-MS(±), elemental analysis and single-crystal X-ray diffraction, revealing distinct types of dicopper(II) units. The structures of 1 and 2 are further extended by intermolecular hydrogen bonds giving rise to 3D or 2D H-bonded nets with a pcu and sql topology, respectively. Both compounds act as efficient pre-catalysts for the mild homogeneous oxidation, by aqueous H2O2 in MeCN/H2O medium, of different cycloalkanes to the corresponding cyclic alcohols and ketones, which are obtained in up to 34% total yields (based on alkanes). The influence of various reaction parameters such as the amount and type of pre-catalyst and acid promoter, solvent composition and substrate scope were investigated, which also show that the oxidation of cycloalkanes and the activity of a catalytic system can be restarted upon addition of new portions of oxidant and substrate. Besides, an unusual promoting role of water was found when using both pre-catalysts 1 and 2. The bond-, regio- and stereoselectivity parameters were established using different alkane substrates, supporting a free radical oxidation mechanism. The model 1/H+/H2O2 and 2/H+/H2O2 solutions were investigated by ESI-MS(±), allowing us to propose some possible catalytically active species.

Graphical abstract: New aqua-soluble dicopper(ii) aminoalcoholate cores for mild and water-assisted catalytic oxidation of alkanes

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Publication details

The article was received on 01 Dec 2015, accepted on 03 Feb 2016 and first published on 04 Feb 2016


Article type: Paper
DOI: 10.1039/C5CY02084K
Author version available: Download Author version (PDF)
Citation: Catal. Sci. Technol., 2016,6, 4584-4593
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    New aqua-soluble dicopper(II) aminoalcoholate cores for mild and water-assisted catalytic oxidation of alkanes

    T. A. Fernandes, C. I. M. Santos, V. André, S. S. P. Dias, M. V. Kirillova and A. M. Kirillov, Catal. Sci. Technol., 2016, 6, 4584
    DOI: 10.1039/C5CY02084K

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