Ferromagnetically-coupled decanuclear, mixed-valence [Mn10O4(N3)4(hmp)12]2+ [hmpH = 2-(hydroxymethyl)pyridine] clusters with rare T symmetry and an S = 22 ground state

The amalgamation of azide (N3-) and 2-(hydroxymethyl)pyridine (hmpH) ligands in Mn cluster chemistry has been further investigated. The reactions of hmpH, NaN3 and Et3N with Mn(NO3)2 · H2O or Mn(ClO4)2 · 6H2O in MeCN/MeOH affords [Mn4IIMn6IIIO4(N3)4(hmp)12]X2[X=N3-(1),ClO4-(2)]. The Mn10 cation has a tetra-face-capped octahedral topology. The central octahedron comprises six Mn3+ ions, and the eight faces are bridged by four μ3-N3- ions and four μ4-O2− ions. The twelve bridging hmp− groups provide the peripheral ligation. This cation is the first example of μ3-1,1,1 azido ligands bridging exclusively Mn3+ ions, presaging a potentially rich new area of MnIII clusters with high spin values. The [Mn10(μ4-O)4(μ3-N3)4]14+ core has Td symmetry, but the complete [Mn4IIMn6IIIO4(N3)4(hmp)12]2+cation has rare T symmetry, which is crystallographically imposed. Complexes 1 and 2 are completely ferromagnetically coupled, and have a resulting S = 22 ground state, one of the highest yet reported.

The combined use of 2-(hydroxymethyl)pyridine and azido ligands in reactions with simple MnII sources has given two Mn4IIMn6III clusters with a beautiful, high-symmetry structure. The Mn10 cation (see structure: Mn blue, O yellow, N green) is completely ferromagnetically coupled and possesses an S = 22 ground state, one of the highest ever reported.Figure optionsDownload as PowerPoint slide