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Issue 9, 2015
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Synthesis and first use of pyridine-2,6-diylbis(pyrazine-2-ylmethanone) in metal cluster chemistry: a {MnIII3Na2} complex with an ideal trigonal bipyramidal geometry

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Abstract

The successful organic synthesis of a new dipyrazole/pyridine-dicarbonyl organic molecule, namely pyridine-2,6-diylbis(pyrazine-2-ylmethanone) [(pz)CO(py)CO(pz)], followed by its employment in Mn coordination chemistry has yielded the neutral cluster compound [Mn3Na2O(N3)3(L)3] (1), where L2− is the (pz)C(CH2COCH3)(O)(py)C(CH2COCH3)(O)(pz) dianion. The latter group was formed in situ, presumably by the nucleophilic attack of the carbanion CH2COCH3 to the carbonyl carbon atoms of (pz)CO(py)CO(pz), in the presence of Mnn+ ions under basic conditions and in solvent Me2CO. Complex 1 possesses an almost ideal trigonal bipyramidal topology, with the two NaI ions occupying the apical positions and the three MnIII ions residing in the equatorial trigonal plane. The bridging ligation about the metal ions is provided by a μ3-O2− ion and six μ-OR groups from the L2− ligand, while peripheral ligation is completed by three terminal azido groups and the pyridine N and carbonyl O atoms of L2−. Magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the paramagnetic MnIII centres; the use of an anisotropic, equilateral MnIII3 triangle model allowed us to fit the magnetic data and obtain the best-fit parameters: J = −10.8 cm−1, D = −5.3 cm−1, and g = 1.99. The combined results demonstrate the rich chemical reactivity of carbonyl groups and the ability of poly-ketone ligands to stabilize cluster compounds with unprecedented structural motifs and interesting architectures.

Graphical abstract: Synthesis and first use of pyridine-2,6-diylbis(pyrazine-2-ylmethanone) in metal cluster chemistry: a {MnIII3Na2} complex with an ideal trigonal bipyramidal geometry

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Article information


Submitted
29 Nov 2014
Accepted
16 Jan 2015
First published
20 Jan 2015

Dalton Trans., 2015,44, 4318-4327
Article type
Paper

Synthesis and first use of pyridine-2,6-diylbis(pyrazine-2-ylmethanone) in metal cluster chemistry: a {MnIII3Na2} complex with an ideal trigonal bipyramidal geometry

D. P. Giannopoulos, C. Wilson-Konderka, K. J. Gagnon, S. J. Teat, A. Escuer, C. Metallinos and T. C. Stamatatos, Dalton Trans., 2015, 44, 4318
DOI: 10.1039/C4DT03666B

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