Two novel mixed-valent manganese (Mn-II/Mn-III) cluster compounds were synthesized in solvothermal reactions and characterized by single-crystal X-ray diffraction, bond valence sum calculations, IR spectra, elemental analysis, and magnetic measurements. Compound 1 is a Mn-19 cluster with a cylindrical core structure. Compound 2 possess a Mn-16 core where all of the manganese sites have unique ligation environments. The magnetic measurements on both compounds indicate dominant antiferromagnetic interactions between the metal centers.