Issue 41, 2010

Self-assembled dicopper(ii) diethanolaminate cores for mild aerobic and peroxidative oxidation of alcohols

Abstract

The new dicopper(II) complexes [Cu2(μ-Hmdea)2(NCS)2] (1) and [Cu2(μ-Hedea)2(N3)2]·(H2O)0.25 (2) with the {Cu2(μ-O)2} diethanolaminate cores have been easily generated by aqueous medium self-assembly reactions of copper(II) nitrate with N-methyl- or N-ethyldiethanolamine (H2mdea or H2edea, respectively), in the presence of sodium thiocyanate (for 1) or sodium azide (for 2) as ancillary ligands sources. They have been isolated as air-stable crystalline solids and fully characterized by IR and UV-vis spectroscopies, ESI-MS(+), elemental and single-crystal X-ray diffraction analyses. The latter complex also features a fourfold linkage of neighbouring dimeric units via strong intermolecular O–H⋯O hydrogen bonds, giving rise to the formation of tetracopper aggregates. The catalytic activity of compounds 1 and 2 has been studied for the mild (50–80 °C) and selective oxidations of alcohols, namely for (i) the aerobic aqueous medium oxidation of benzyl alcohols to benzaldehydes, mediated by TEMPO radical, and for (ii) the solvent-free oxidation of secondary alcohols to ketones by t-BuOOH under microwave (MW) irradiation. Complex 2 shows the highest efficiency in both oxidation systems, resulting in up to 99% molar yields (based on the alcohol substrate) of products. In addition, remarkably high values of TON (1020) and TOF (4080 h−1) have been achieved in the MW-assisted peroxidative oxidation of 1-phenylethanol to acetophenone (model reaction). Attractive green features of these catalytic systems include the operation in aqueous or solvent-free reaction medium, under mild conditions and with high yields and selectivities, using Cu catalyst precursors that are readily available by self-assembly in water of simple chemicals.

Graphical abstract: Self-assembled dicopper(ii) diethanolaminate cores for mild aerobic and peroxidative oxidation of alcohols

Supplementary files

Article information

Article type
Paper
Submitted
14 May 2010
Accepted
05 Aug 2010
First published
16 Sep 2010

Dalton Trans., 2010,39, 9879-9888

Self-assembled dicopper(II) diethanolaminate cores for mild aerobic and peroxidative oxidation of alcohols

P. J. Figiel, A. M. Kirillov, M. F. C. Guedes da Silva, J. Lasri and A. J. L. Pombeiro, Dalton Trans., 2010, 39, 9879 DOI: 10.1039/C0DT00472C

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