Download SYNTHESIS, CRYSTAL STRUCTURE AND PROPERTIES OF OXO

SYNTHESIS, CRYSTAL STRUCTURE AND PROPERTIES OF OXO-CENTERED TRINUCLEAR
MANGANESE COMPLEX WITH ETHYL ISONICOTINATE
DULCEVSCAIA Galina
Institute of Chemistry, Academy of Science of Moldova
Reviewer: BACA S., dr.
Keywords: manganese, µ3-oxotrinuclear cluster, carboxylates structure, polynuclear complexes
In the last decades, there has been increasing interest in polynuclear manganese complexes with respect to
their remarkable magnetic properties and potential applications in oxidation catalysis and biomimetic chemistry.
Interaction of hexanuclear mixed-valence manganese [Mn6O2(O2CCMe3)10(Me3CCO2H)4] complex with ethyl
isonicotinate (ein) in the presence of MnO4 ions generated the formation of new 3-oxo centered mixed-valence
trinuclear complex [Mn3O(O2CCMe3)6(ein)3] (1). The new complex has been characterized by IR spectroscopy, Xray crystallography and thermal analysis. The IR spectrum of complex 1 has strong and broad bands in the
15881570 and 13731359 cm1 regions, which are due to asymmetric and symmetric vibrations of the coordinated
carboxylate groups of the pivalate ligand, respectively. X-ray diffraction analysis showed that complex 1 consists of
the trinuclear [Mn3O(O2CCMe3)6] cluster with the three metal atoms bridged by six pivalate groups. At each axial
position there is an ethyl isonicotinate molecule (Fig. 1). Each Mn atom is coordinated by an oxygen atom of the
central triangle, four oxygen atoms from bridging pivalate ligands, and one nitrogen atom of ethyl isonicotinate.
Based on the charge neutrality of the [Mn3O(O2CCMe3)6(ein)3] cluster the Mn oxidation states in this complex are
given as [MnIII2MnII]. As expected for its lower oxidation state, the position of the Mn II atom can be assigned on the
basis of its longer metal--oxygen and metal-ligand bond distances compared with the Mn III atoms. From these data
Mn(2) is assigned as the MnII center, whereas Mn(1) and Mn(3) atoms are MnIII centers. The MnIIIO(1) bond
distances are in the range 1.8491.859 Å, which is in agreement with the other -oxo trinuclear carboxylates [1].
For MnII atom this distance is longer and equals to 2.011 Å. The four MnOcarb distances around MnIII and MnII
atoms are in the range of 1.9812.150 Å and 2.0782.170 Å, respectively. Ethyl isonicotinate has uncoordinated
oxygen atom which can participate in the coordination to other metal centers and form different polymeric
structures.
Fig. 1. A view of the structure (left) and a parking diagram (right) of compound 1.
Reference
1. S. Baca, H. Stoeckli-Evans, C. Ambrus, S. Malinovskii, I. Malaestean, N. Gerbeleu, S. Decurtins . //Polyhedron,
2006, Vol. 25, P. 3617-3627
Acknowledgements: Financial support was provided by the German Federal Ministry of Education and Research
(Grant MDA 08/022) and the Academy of Sciences of Moldova (Grant No. 09.820.05.10GF). The author
acknowledges the assistance of Dr. A. Ellern in the collection of crystallographic data set.