Treatments of Mn(O2CR)(2) (R = Me, Ph) with NBu4MnO4 in CH3CN or CH3CN/CH2Cl2 in the presence of acetic acid, delta(1)-cyclohexenephosphonic acid (C6H9PO3H2), and 2,2'-bipyridine or 1,10-phenanthroline result in three novel dodecamanganese(III) clusters [Mn12O8(O2CMe)(6)(O3PC6H9)(7)(bipy)(3)] (1), [Mn12O8(O2CPh)(6)(O3PC6H9)(7)(bipy)(3)] (2), and [Mn12O8(O2CPh)(6)(O3PC6H9)(7)(phen)(3)] (3). They have a similar Mn-12 core of [Mn-12(III)(mu(4)-O)(3)(mu(3)-O)(5)(mu-O3P)(3)] with a new type of topologic structure. Solid-state dc magnetic susceptibility measurements of complexes 1-3 reveal that dominant antiferromagnetic interactions are propagated between the magnetic centers. The ac magnetic measurements suggest an S = 2 ground state for compounds 1 and 3 and an S = 3 ground state for compound 2.