Novel hydrogenmaleato molybdenum(V) complexes based on a dinuclear metal–metal bonded unit: syntheses and structural characterization of (PyH) 3 [Mo 2 O 4 Cl 4 (OOCCH CHCOOH)] and (PyH) 3 [Mo 2 O 4 Br 4 (OOCCH CHCOOH)]·CH 3 CN

Abstract Reactions of pyridinum hydrogenmaleate with mononuclear oxohalomolybdates produced (PyH) 3 [Mo 2 O 4 X 4 (OOCCH CHCOOH)] (X=Cl, Br), the first molybdenum(V) complexes with hydrogenmaleato ligand. The X-ray structure analysis revealed in both the {Mo 2 O 4 } 2+ core with hydrogenmaleate in a μ 2 -bis(monodentate) binding mode forming a third bridge between a pair of molybdenum atoms linked by a single metal–metal bond. A pair of halo ligands completes a distorted octahedral environment of each metal in the {Mo 2 O 4 } 2+ unit.