Mn3 Single-Molecule Magnets and Mn6/Mn9 Clusters from the Use of Methyl 2-Pyridyl Ketone Oxime in Manganese Phosphinate and Phosphonate Chemistry.

The syntheses, structures, and magnetochemical properties are reported for five new Mn clusters: [MnIII3O(O2PPh2)3(mpko)3](ClO4) (1), [MnIII3O(O2PPh2)3(ppko)3](ClO4) (2) [MnIII6O2(OMe)4(O2PPh2)4(mpko)4](ClO4)2 (3), [MnIII8MnIIO6(O2CMe)7(O3PPh)2(mpko)3(H2O)] (4), and [MnIII2MnIIO(mpko)3(H2O)4(ClO4)2](ClO4) (5), where mpko- (or ppko-) is the anion of methyl (or phenyl) 2-pyridyl ketone oxime. 1 was obtained by carboxylate substitution on [MnIII3O(O2CMe)3(mpko)3](ClO4) by treatment with diphenylphosphinic acid (Ph2PO2H). The comproportionation reaction between Mn(ClO4)2 and NBun4MnO4 in the presence of Ph2PO2H and ppkoH in EtOH, or mpkoH in MeOH, led to 2 and 3, respectively. 4 was obtained as was 3, but with phenylphosphonic acid (PhPO3H2) instead of Ph2PO2H. 5 was obtained by aerial oxidation of Mn(ClO4)2 in the presence of mpkoH. 1 and 2 contain a triangular Mn3 core, 3 comprises the fusion of two Mn3 units of 1 by MeO- bridges, and 4 has a cagelike structure. 5 is similar to 1 in possessing a triangular core. Variable-temperature, solid-state direct-current (dc) and alternating-current (ac) magnetic data were collected on 1-5: 1 and 2 exhibit ferromagnetic Mn····Mn exchange interactions, S = 6 ground states, and are new single-molecule magnets (SMMs). 3-5 possess S = 4, 5/2, and 5/2 ground states, respectively, from dominant antiferromagnetic interactions. Fits of dc magnetization data in the 1.8-10.0 K and 10-70 kG ranges gave D and g values of: -0.29(2) cm-1 and 1.94(1) for 1, -0.38(2) cm-1 and 1.99(1) for 2, -0.29(2) cm-1 and 1.96(1) for 3, -1.26(4) cm-1 and 1.99(2) for 4, -1.41(4) cm-1 and 1.98(2) for 5, where D is the axial zero-field splitting parameter.