[Mn<sub>7</sub>O<sub>5</sub>(OR)<sub>2</sub>(O<sub>2</sub>CPh)<sub>9</sub>(terpy)] (R = Me, CH<sub>2</sub>Ph) Complexes with a Fused Cubane/Butterfly Core and an <i>S</i> = 6 Ground-State Spin
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Two new heptanuclear Mn clusters, [Mn7O5(OMe)2(O2CPh)9(terpy)] (1) and [Mn7O5(OCH2Ph)2(O2CPh)9(terpy)] (2), were prepared from the partial alcoholysis of the trinuclear complex [Mn3O(O2CPh)6(py)2(H2O)] (3) in the presence of terpy (terpy = 2,2‘:6‘,2‘ ‘-terpyridine). Complexes 1 and 2 crystallize in the triclinic P1̄ and the orthorhombic Pbca space groups, respectively. The clusters are both mixed valent, containing three Mn oxidation states: MnIV, 5MnIII, and MnII. The Mn ions are held together by nine doubly bridging benzoates, four μ3-O2- ions, one μ5-O2- ion, and either two μ-MeO- (1) or two μ-PhCH2O- (2) groups. The single terpy chelate in each complex is attached to the MnII ion. The core topology is novel and very unusual, comprising a cubane and a butterfly unit fused by sharing a MnIII and the μ5-O2- ion. Solid-state dc and ac magnetic susceptibility studies establish that complexes 1 and 2 both possess an S = 6 ground-state spin. Fits of variable-temperature and -field magnetization data gave S = 6, g = 1.88, and D = −0.21 cm-1 for 1 and S = 6, g = 1.86, and D = −0.18 cm-1 for 2. Single-crystal magnetization vs dc field scans down to 0.1 K for 2 show only very little hysteresis at 0.1 K.
