Cyanate groups in higher oxidation state metal cluster chemistry: Mixed-valence (II/III) Mn16 and Mn18 clusters
Date
2016Author
Alexandropoulos, Dimitris I.Moushi, Eleni E.
Papatriantafyllopoulou, Constantina
Beavers, Christine M.
Teat, S. J.
Tasiopoulos, Anastasios J.
Christou, George
Stamatatos, Theocharis C.
Source
PolyhedronVolume
108Pages
131-142Google Scholar check
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The employment of cyanato (OCN-) group in high oxidation state manganese cluster chemistry, in conjunction with carboxylate ions and the organic chelating/bridging ligand 2-(hydroxymethyl)pyridine (hmpH), is reported. The syntheses, crystal structures, and magnetochemical characterization are described for [Mn16O8(OR)4(OCN)4(O2CMe)12(hmp)6(ROH)2] (R = Me (1), Et (2)) and [Mn18O14(O2CR)18(hmp)4(hmpH)2(H2O)2] (R = Me (3), Et (4)). The 2:1:1:1 reactions of Mn(O2CMe)2·4H2O, hmpH, NaOCN and NEt3 in solvent MeOH or EtOH afford the isostructural complexes [Mn16O8(OR)4(OCN)4(O2CMe)12(hmp)6(ROH)2] (R = Me (1), Et (2)). The [Mn16(μ4-O)4(μ3-O)4(μ-OMe)4(μ3-OR)6(μ-OR)6]10+ core of representative complex 1 comprises a MnII 4MnIII 4 double-cubane subunit attached on either side to two symmetry-related MnIIMnIII 3 defective dicubanes. A similar reaction of Mn(O2CR)2·4H2O, hmpH, NaOCN and NEt3, but in solvent MeCN, led instead to the formation of [Mn18O14(O2CR)18(hmp)4(hmpH)2(H2O)2] (R = Me (3), Et (4)). Compounds 3 and 4 are very similar to each other and can be described as a central [MnIII 4(μ-O)6] rodlike subunit attached on either side to two symmetry-related [Mn7O9] subunits. Variable-temperature, solid-state dc and ac magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions in all compounds, and possible S = 2 or 1 (for 1 and 2) and S = 0 (for 3 and 4) ground state spin values. The combined results demonstrate the ability of cyanato groups to facilitate the formation of new polynuclear MnII/III complexes with structures different than these obtained from the use of the related azides. © 2015 Elsevier Ltd. All rights reserved.