This work presents a straightforward methodology to achieve small linear trinuclear molecules based on the CoII-carboranylcarboxylate system obtained by carving a 1D polynuclear analogous system with the use of diethylether. The reaction of the carboranylcarboxylic ligand, 1-CH3-2-CO2H-1,2-closo-C2B10H10 (LH) with different cobalt salts leads to the polynuclear compound [Co2(μ-H2O)(1-CH3-2-CO2-1,2-closo-C2B10H10)4(THF)4], 1 and the polymeric [Co(μ-H2O)(1-CH3-2-CO2-1,2-closo-C2B10H10)2]n(H2O)n2. This latter 1D chain has been obtained by an unprecedented synthetic strategy for the isolation of cobalt(II) compounds. [Co3(μ-H2O)2(1-CH3-2-CO2-1,2-closo-C2B10H10)6(H2O)2(C4H10O)2], 3 is formed by the dissociation of the polymeric structure that forms 2 when a mild coordinating solvent such as diethylether is added. These compounds have been characterized by analytical and spectroscopic techniques. X-ray analysis of 1 and 3 revealed that 1 presents a dinuclear structure whereas 3 is trinuclear; in both cases a six-coordinated CoII compound with water molecules bridging each of the two CoII centres has been observed. The magnetic properties of 1 and 3 show a weak antiferromagnetic behaviour, respectively, between the CoII centres mediated by two carboxylate ligands and a molecule of water.