The first oxalate-bridged one-dimensional polymer containing MoV2 dimers with single metal–metal bonds. Syntheses and structures of (MeNC5H5)2n[Mo2O4(C2O4)Cl2]n and (3-MePyH)2n[Mo2O4(C2O4)Cl2]n

Hydrothermal reactions of mononuclear oxochloromolybdate(V) with oxalic acid in alcohol (methanol or 2-propanol) and pyridines (pyridine or 3-methylpyridine) media have afforded two polymeric compounds of molybdenum(V): N-methylpyridinum catena-μ-oxalato-O1,O2:O1′,O2′-(dichloro-di-μ-oxo-dioxodimolybdate(V)), (MeNC5H5)2n[Mo2O4(C2O4)Cl2]n1 and 3-methylpyridinium catena-μ-oxalato-O1,O2:O1′,O2′-(dichloro-di-μ-oxo-dioxodimolybdate(V)), (3-MePyH)2n[Mo2O4(C2O4)Cl2]n2. The compounds were fully characterized by X-ray structural analysis, infrared and NMR spectroscopy. The essentially isostructural anionic chains in 1and 2 are built of alternating pairs of {Mo2O4}2+ containing edge-sharing octahedra and planar oxalates giving a Mo ∶ oxalate ratio of 2. The bisbidentate oxalate acts as a bridge between two dinuclear subunits. The formation of a N-methylpyridinium cation from methanol and pyridine in the presence of molybdenum(V) and oxalic acid has not been documented before.