Syntheses, Spectroscopies and Structures of Molybdenum(VI) Complexes with Homocitrate

Initial investigations into the possible role of homocitric acid in iron molybdenum cofactor (FeMo-co) of nitrogenase
lead us to isolate and characterize two tetrameric molybdate(VI) species. The complexes K2(NH4)2[(MoO2)4O3(R,S-Hhomocit)2]·6H2O (1) and K5[(MoO2)4O3(R,S-Hhomocit)2]Cl·5H2O (2) (homocitric acid = H4homocit, C7H10O7) are
prepared from the reactions of acyclic homocitric acid and molybdates, which represent the first synthetic structural
examples of molybdenum homocitrate complexes. The homocitrate ligand trapped by tetranuclear molybdate
coordinates to the molybdenum(VI) atom through α-alkoxy and α-, β-carboxy groups. The physical properties,
structural parameters, and their possible biological relevances are discussed.