Molecular complexes of Ca, Sr, and Ba with the reduced forms of 3,6-di-tert-butyl-o-benzoquinone as ligands (catecholate, 3,6-Cat2–, or semiquinone 3,6-SQ–‧) were synthesized and structurally characterized. Trinuclear complexes [M3(3,6-Cat)3(thf)6] (1, M = Ca; 2, M = Sr) or tetranuclear complex [Ba4(3,6-Cat)4(thf)6] (3) crystallize from tetrahydrofuran (thf) solutions. In the structures of 1 and 2 metal atoms form a nearly right triangle with two µ3-bridging 3,6-Cat ligands; in 3, the metal atoms form a tetrahedron contracted along a twofold axis, and all the catecholates are µ3-bridging. In nonpolar media the complexes 1–3 lose coordinated thf, upon which 1 is converted into complex [Ca4(3,6-Cat)4(thf)4] (4), structurally similar to 3. Complex 1 is oxidized by one equivalent of the quinone to yield mixed-ligand complex [Ca3(3,6-SQ)2(3,6-Cat)2(thf)4] (5), structurally similar to 1. Successive oxidation by the quinone leads to dissociation to mononuclear species, [Ca(3,6-SQ)2(thf)3] (5), which possesses pentagonal-bipyramidal coordination with two semiquinolate ligands lying in an equatorial plane. Solution behavior of the complexes is studied by NMR (for catecholates) and EPR (for semiquinolates) spectroscopy.

Язык оригиналаанглийский
Страницы (с-по)4373-4383
Число страниц11
ЖурналEuropean Journal of Inorganic Chemistry
Номер выпуска39-40
СостояниеОпубликовано - 31 окт 2019

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