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Issue 6, 2009
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Employment of methyl 2-pyridyl ketone oxime in manganese non-carboxylate chemistry: MnII2MnIV and MnII2MnIII6 complexes

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Abstract

The employment of the anion of methyl 2-pyridyl ketone oxime (mpko) as a tridentate chelating/bridging ligand in manganese chemistry is described. The inorganic anion (Br, ClO4) used in the reaction affects the identity of the product. The reaction of MnBr2 and one equivalent of mpkoH in the presence of a base affords [Mn3(OMe)2(mpko)4Br2] (3), which is mixed-valence (2MnII, MnIV). The central MnIV atom in each of the two, crystallographically independent, centrosymmetric molecules is coordinated by four oximate oxygen atoms belonging to the η111:μ mpko ligands, and two η1MeO groups, while six coordination at each terminal MnII atom is completed by four nitrogen atoms belonging to the ‘chelating’ part of two mpko ligands, and one Br ion. The MnII atoms have trigonal prismatic coordination geometry. The reaction of Mn(ClO4)2·6H2O, mpkoH and OH (1:2:1) in MeOH gives [Mn8O4(OMe)(mpko)9(mpkoH)](ClO4)4 (4), which is also mixed-valence (2MnII, 6MnIII) and possesses the novel [Mn83-O)4(μ-OMe)(μ-OR″)2]11+ core. The latter possesses a U-shaped sequence of four fused {MnIIMnIII23-O)}6+ triangular units, with a MnIII-MnIII edge being shared between the central triangles. Variable-temperature, solid-state dc and ac magnetic susceptibility studies were carried out on complexes 3 and 4. The dc susceptibility data for 3 in the 5.0–300 K range have been fit to a model with two J values, revealing weak ferromagnetic MnIIMnIV (J = +3.4 cm−1) and MnIIMnII (J′ = +0.3 cm−1) exchange interactions. Fitting of the magnetization vs. H/T data by matrix diagonalization and including only axial anisotropy (ZFS, D) gave ground state spin (S) and D values of S = 13/2, D = +0.17 cm−1 for 3 and S = 3, D = −0.09 cm−1 for 4. The combined work demonstrates the usefulness of mpko in the preparation of interesting Mn clusters, without requiring the co-presence of carboxylate ligands.

Graphical abstract: Employment of methyl 2-pyridyl ketone oxime in manganese non-carboxylate chemistry: MnII2MnIV and MnII2MnIII6 complexes

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Supplementary files

Article information


Submitted
08 Aug 2008
Accepted
28 Oct 2008
First published
09 Jan 2009

Dalton Trans., 2009, 1004-1015
Article type
Paper

Employment of methyl 2-pyridyl ketone oxime in manganese non-carboxylate chemistry: MnII2MnIV and MnII2MnIII6 complexes

C. C. Stoumpos, T. C. Stamatatos, H. Sartzi, O. Roubeau, A. J. Tasiopoulos, V. Nastopoulos, S. J. Teat, G. Christou and S. P. Perlepes, Dalton Trans., 2009, 1004
DOI: 10.1039/B813828A

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