New copper(II) tetramer with arylhydrazone of barbituric acid and its catalytic activity in the oxidation of cyclic C5–C8 alkanesстатья
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Дата последнего поиска статьи во внешних источниках: 28 октября 2016 г.
Аннотация:2-(2-(2,4,6-Trioxotetrahydropyrimidin-5(2H)-ylidene)hydrazinyl)terephthalic acid (H5L) was synthesized
by azocoupling of diazonium salts of 2-aminoterephthalic acid with barbituric acid and characterized
by IR, 1H and 13C NMR spectroscopies and ESI-MS analysis. In solution and solid state, H5L exists in
the hydrazone form. The reaction of H5L with copper(II) nitrate hydrate in methanol affords the tetramer
species [Cu2(l2-1jNOO0:2jO0O00-H3L)2]2 (1) where carboxylate groups bridge two Cu(II) centers in a
bridging chelate l2-(O,O0,O0) fashion, giving rise to a cyclic Cu4O4 core. A rare and intense intermolecular
non-covalent interaction of the type Ocarboxylic(lone pair) p(pyrimidine), with O centroid distance of
2.705 Å, was found in 1. In addition, medium intense NAH O and OAH O contacts expand the structure
to a 3D network. Compound 1 behaves as efficient catalyst in the mild oxidation, by aqueous H2O2 in
acidic MeCN/H2O media, of different cyclic C5–C8 alkanes to produce the corresponding alcohols and
ketones. Overall product yields up to ca. 25% (based on alkane) were achieved.