As revealed by the X-ray structure analysis, the half-neutralized form of the dicarboxylic acid, the dmsH − ion, coordinated to the well-known {Mo 2 O 4 } 2+ core in the syn-syn bidentate bridging manner. In both compounds, the non-ionized terminus of the ligand, the COOH function, participated in hydrogen-bonding interactions. The incorporation of the chloride counteranion in 2, prevented the formation of the common "carboxylic acid dimer" which was observed for 1. Instead, a hydrogen-bonded linkage of the COOH function with the chloride occurred.