The charge-neutral mixed-valent coordination clusters [MnIII 2MnII 4O2(piv)10(L)4], where Hpiv= pivalic acid and L is neutral monodentate ligand, represent an attractive supermolecular building block [1, 2] for assembly of cluster-based polymeric materials [3, 4] because their properties may be modified by judicious choice of the capping ligands L and possibility to replace L completely or partially by spacer exo-bidentate ligands. Two new hexanuclear manganese clusters, [Mn6O2(piv)10(H2O)4] • n(H2O) (1) and [Mn6O2(piv)10(H2O)(MeOH)3] • (MeCN) • n(H2O/MeOH) (2), have been synthesized under ultrasonic irradiation in different solvents. Compound 1 crystallizes in the monoclinic P21/n space group, a = 16.227, b = 21.868, c = 23.758 Å, β = 95.91°, whereas compound 2 crystallizes in the triclinic P-1 space group, a = 13.759, b = 14.562, c = 22.352 Å, α = 80.84, β = 87.29, γ = 89.69°. The clusters contain a {MnII 4MnIII 2O2}10+ core of two edge sharing Mn4 tetrahedra with a μ4-O2-ion in the center of each tetrahedron. Peripheral ligation is provided by ten bridging pivalate monoanionic ligands. Four of them coordinate in a μ3-mode and bridge three Mn centers, whereas the other six each bridge two Mn centers in a μ2-mode. Within the core, the two central Mn centers are in the oxidation state +3, and the four terminal Mn atoms are in the lower oxidation state +2. All MnII/III ions in the {Mn6} unit are six-coordinated with a distorted octahedral O6 environment. 1 2 Fig. View of clusters, ter-butyl fragments of pivalate ligands are omitted for clarity. The crystal structure of I and II revealed large solvent acceptable voids: 2088 Å3 (or 25% of total unit cell volume 8386 Å3) and 855 Å3 (or 20% of total unit cell volume 4417 Å3) respectively. The disordered solvent molecules have not been localized in I and only partially in II.