The first oxalate-bridged one-dimensional polymer containing Mo₂^v dimers with single metal-metal bonds. Syntheses and structures of (MeNC₅H₅)[Mo₂O₄(C₂O₄ )Cl₂]_n and (3-MePyH)_2n-[Mo₂O₄(C₂O₄)C l₂]_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-(C ₂O₄)Cl₂]_n 1 and 3-methylpyridinium catena-μ-oxalato-O¹,O²: O¹′,O²′-(dichloro-di-μ-oxo-dioxodimolybdate (v)), (3-MePyH)_2n[Mo₂O₄(C₂O₄)Cl ₂]_n 2. The compounds were fully characterized by X-ray structural analysis, infrared and NMR spectroscopy. The essentially isostructural anionic chains in land 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.