Structures and magnetic properties of tetranuclear nickel(II) complexes with unusual mu3-1,1,3 azido bridges |
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Authors: | Meyer Franc Demeshko Serhiy Leibeling Guido Kersting Berthold Kaifer Elisabeth Pritzkow Hans |
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Affiliation: | Institut für Anorganische Chemie, Georg-August-Universit?t G?ttingen, Tammannstrasse 4, 37077 G?ttingen, Germany. franc.meyer@chemie.uni-goettingen.de |
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Abstract: | Pyrazolate-based dinucleating ligands with thioether-containing chelate arms have been used for the synthesis of a family of novel tetranuclear nickel(II) complexes [L2Ni4(N3)3(O2CR)](ClO4)2 that incorporate three azido bridges and one carboxylate (R = Me, Ph). Molecular structures have been elucidated by X-ray crystallography in four cases, revealing Ni4 cores with a unique topology in which two of the azido ligands adopt an unusual mu3-1,1,3 bridging mode. The compounds were further characterized by mass spectrometry, IR spectroscopy, and variable-temperature magnetic susceptibility measurements. Magnetic data analyses indicate a combination of significant intramolecular ferromagnetic and antiferromagnetic exchange interactions that give rise to an overall S(T) = 0 ground state. The sign and the magnitude of the individual couplings have been rationalized in the framework of the common magnetostructural correlations for end-to-end and end-on azido linkages, suggesting that these correlations also remain valid for the respective fragments of multiply bridging mu3-1,1,3 azido ligands. |
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Keywords: | azide ligands magnetic properties molecular magnetism nickel tetranuclear complexes |
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