title: Structures and magnetic properties of tetranuclear nickel(II) complexes with unusual mu3-1,1,3 azido bridges.
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.
authors.affiliation: Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany. franc.meyer@chemie.uni-goettingen.de
authors.forename: Franc
authors.initials: F
authors.lastname: Meyer
authors.forename: Serhiy
authors.initials: S
authors.lastname: Demeshko
authors.forename: Guido
authors.initials: G
authors.lastname: Leibeling
authors.forename: Berthold
authors.initials: B
authors.lastname: Kersting
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kaifer
authors.forename: Hans
authors.initials: H
authors.lastname: Pritzkow