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The first coordination compound of deprotonated 2-bromonicotinic acid: crystal structure of a dinuclear paddle-wheel copper(II) complex.

ABSTRACT: A copper(II) dimer with the deprotonated anion of 2-bromonicotinic acid (2-BrnicH), namely, tetrakis(?-2-bromonicotinato-?2 O:O?)bis[aquacopper(II)](Cu—Cu), [Cu2(H2O)2(C6H3BrNO2)4] or [Cu2(H2O)2(2-Brnic)4], (1), was prepared by the reaction of copper(II) chloride dihydrate and 2-bromonicotinic acid in water. The copper(II) ion in 1 has a distorted square-pyramidal coordination environment, achieved by four carboxylate O atoms in the basal plane and the water molecule in the apical position. The pair of symmetry-related copper(II) ions are connected into a centrosymmetric paddle-wheel dinuclear cluster [Cu?Cu = 2.6470?(11)?Å] via four O,O?-bridging 2-bromonicotinate ligands in the syn-syn coordination mode. In the extended structure of 1, the cluster molecules are assembled into an infinite two-dimensional hydrogen-bonded network lying parallel to the (001) plane via strong O—H?O and O—H?N hydrogen bonds, leading to the formation of various hydrogen-bond ring motifs: dimeric R 2 2(8) and R 2 2(16) loops and a tetrameric R 4 4(16) loop. The Hirshfeld surface analysis was also performed in order to better illustrate the nature and abundance of the intermolecular contacts in the structure of 1.

SUBMITTER: Politeo N

PROVIDER: S-EPMC7001845 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Project description:The experimental electron-density distribution in two isostructural complexes, tetrakis(?2-acetato)diaquadicopper(II) [H2OCu(ac)2Cu(ac)2H2O] and tetrakis(?2-acetato)diaquadichromium(II) [H2OCr(ac)2Cr(ac)2H2O], has been studied and compared. The experimental electron density distribution in two isostructural and isomorphous complexes, tetrakis(?2-acetato)diaquadicopper(II) [H2OCu(ac)2Cu(ac)2H2O] (I) and tetrakis(?2-acetato)diaquadichromium(II), [H2OCr(ac)2Cr(ac)2H2O] (II), has been obtained from high-resolution X-ray diffraction data in order to shed light on the bonding properties in the compounds studied. It has been shown that from accurate X-ray data it is possible to discuss the bonding capability of the metal atom (Cu/Cr) and the ligands in these complexes. A comparison of results obtained from averaged and non-averaged X-ray data demonstrates that using the non-averaged data and introducing an anisotropic correction for secondary extinction errors provides a more detailed distribution of the electron density in the area of the metal atoms. In both complexes studied, the bonding of the acetate oxygen atom to the central metal atom is significantly affected by the formation of hydrogen bonds. The electron density and its Laplacian at the bond critical point of metal–oxygen coordination bonds for those oxygen atoms not involved in the intermolecular hydrogen bonds are approximately 10% larger compared with the case when oxygen atoms take part in hydrogen bonds with the neighboring water molecules. It is shown that metal–oxygen bonds in a quasi-equatorial plane are typical coordination bonds and differ significantly from the apical metal–oxygen bond. Metal–metal interaction with a small positive value of the electron density Laplacian at this bond critical point is mainly of electrostatic character. The metal–metal interaction is definitely not a bond according to the classical definition. Based on a search of the Cambridge Structural Database, it can be argued that there are four typical coordination bonds in the [CuO6] chromophore, similar to the four Cu—O coordination bonds in the basal plane of the CuO5 pyramid in one of the complexes under study.

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The first coordination compound of deprotonated 2-bromonicotinic acid: crystal structure of a dinuclear paddle-wheel copper(II) complex.

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The first coordination compound of deprotonated 2-bromo­nicotinic acid: crystal structure of a dinuclear paddle-wheel copper(II) complex.

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OmicsDI is part of the ELIXIR infrastructure

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The first coordination compound of deprotonated 2-bromonicotinic acid: crystal structure of a dinuclear paddle-wheel copper(II) complex.