TY - JOUR

T1 - Structural Diversity of Calcium, Strontium, and Barium Complexes with Reduced Forms of the 3,6-Di-tert-butyl-o-benzoquinone Ligand

AU - Sinitsa, Dmitry K.

AU - Sukhikh, Taisiya S.

AU - Petrov, Pavel A.

AU - Nadolinny, Vladimir A.

AU - Konchenko, Sergey N.

AU - Pushkarevsky, Nikolay A.

N1 - Publisher Copyright: © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

PY - 2019/10/31

Y1 - 2019/10/31

N2 - 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.

AB - 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.

KW - Alkaline earth metals

KW - Catecholate

KW - Multinuclear complexes

KW - Redox-active ligands

KW - Semiquinolate

KW - CATECHOLATE

KW - OXIDATION

KW - SINGLE-MOLECULE MAGNET

KW - TRANSITION-METAL-COMPLEXES

KW - SEMIQUINONE

KW - EPR

KW - COPPER(II)

KW - IONS

KW - VALENCE TAUTOMERISM

KW - DERIVATIVES

UR - http://www.scopus.com/inward/record.url?scp=85071651764&partnerID=8YFLogxK

U2 - 10.1002/ejic.201900678

DO - 10.1002/ejic.201900678

M3 - Article

AN - SCOPUS:85071651764

VL - 2019

SP - 4373

EP - 4383

JO - European Journal of Inorganic Chemistry

JF - European Journal of Inorganic Chemistry

SN - 1434-1948

IS - 39-40

ER -