In the quest for new synthetic strategies for designing new magnetic metal–organic frameworks, two manganese(II) butyrate-based compounds have been synthesized and characterized for the first time. Both compounds have been studied in depth by single crystal X-ray diffraction and powder neutron diffraction, thermogravimetric analysis, differential scanning calorimetry, SQUID magnetometry, and FTIR spectroscopy. The structures of both compounds are different from the typical lamellar one of most of metal alkanoates. The first one (hexamanganese(II) hydroxy undecabutanoate) presents an isostructural solid-to-solid transition at low temperature, with a packing of corrugated layers (2D coordination polymer) in a monoclinic unit cell (P21/n), while the other one (diaqua pentamanganese(II) decabutanoate) shows a 3D framework in a cubic lattice (Ia-3). The magnetic properties of both systems reveal the existence of an overall antiferromagnetic interaction involving an extensive exchange coupling network. These polynuclear complexes show that short metal alkanoates of transition metals, or even, mixed ligand complexes could be a way to design compounds with interesting properties (magnetic, porous, ...).