Mn Single-Molecule Magnets and Mn/Mn 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: MnO(OPPh)(mpko) (1), MnO(OPPh)(ppko) (2) MnO(OMe)(OPPh)(mpko) (3), [MnMnO(OCMe)(OPPh)(mpko)(HO)] (4), and MnMnO(mpko)(HO)(ClO) (5), where mpko (or ppko) is the anion of methyl (or phenyl) 2-pyridyl ketone oxime. 1 was obtained by carboxylate substitution on MnO(OCMe)(mpko) by treatment with diphenylphosphinic acid (PhPOH). The comproportionation reaction between Mn(ClO) and NBuMnO in the presence of PhPOH and ppkoH in EtOH, or mpkoH in MeOH, led to 2 and 3, respectively. 4 was obtained as was 3, but with phenylphosphonic acid (PhPOH) instead of PhPOH. 5 was obtained by aerial oxidation of Mn(ClO) in the presence of mpkoH. 1 and 2 contain a triangular Mn core, 3 comprises the fusion of two Mn 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, /, and / 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 and 1.94(1) for 1, -0.38(2) cm and 1.99(1) for 2, -0.29(2) cm and 1.96(1) for 3, -1.26(4) cm and 1.99(2) for 4, -1.41(4) cm and 1.98(2) for 5, where D is the axial zero-field splitting parameter.