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 P (1) over bar and the orthorhombic Pbca space groups, respectively. The clusters are both mixed valent, containing three Mn oxidation states: Mn-IV, 5Mn(III), and Mn-II. The Mn ions are held together by nine doubly bridging benzoates, four mu(3)-O2- ions, one mu(5)-O2- ion, and either two mu-MeO-(1) or two mu-PhCH2O- (2) groups. The single terpy chelate in each complex is attached to the Mn-II ion. The core topology is novel and very unusual, comprising a cubane and a butterfly unit fused by sharing a Mn-III and the mu(5)-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.