title: Syntheses, crystal structures and biological relevance of glycolato and S-lactato molybdates.
abstract: Glycolato and S-lactato complexes containing the dioxomolybdenum(VI) moiety have been synthesized for studies on the role of the alpha-hydroxycarboxylato anion in the iron molybdenum cofactor of nitrogenase. The ligands in these complexes, vis K2[MoO2(glyc)2].H2O (H2glyc=glycolic acid, C2H4O3) (1) and (Na2[MoO2(S-lact)2])3.13H2O (H2lact=lactic acid, C3H6O3) (2) chelate through their alpha-alkoxyl and alpha-carboxyl oxygen atoms. In contrast, octanuclear K6[(MoO2)8(glyc)6(Hglyc)2].10H2O (3) formed by the reduction of the glycolato complex (1), features three different ligand binding modes: (i) non-bridging and bridging bidentate coordination of alpha-alkoxyl and alpha-carboxyl groups, and (ii) bidentate bridging using alpha-carboxyl group, leaving the alpha-alkoxyl group free. The octanuclear skeleton shows strong metal-metal interactions. The coordination modes in (1) and (2) mimic that of homocitrate to the iron molybdenum cofactor (FeMo-co) of nitrogenase. The bidentate coordination of alpha-alkoxyl and alpha-carboxyl groups shows that bond of alpha-carboxyl group to Mo is less susceptible to the oxidation state of molybdenum compared with the Mo-alpha-alkoxyl bond. This is supported by the dinuclear coordination of alpha-carboxyl group with free alpha-alkoxyl group in glycolato molybdate(V) (3).
authors.affiliation: Department of Chemistry and State Key Laboratory for Physical Chemistry of Solid Surface, Xiamen University, Xiamen 361005, PR China. zhzhou@xmu.edu.cn
authors.forename: Zhao-Hui
authors.initials: ZH
authors.lastname: Zhou
authors.forename: Shu-Ya
authors.initials: SY
authors.lastname: Hou
authors.forename: Ze-Xing
authors.initials: ZX
authors.lastname: Cao
authors.forename: Hui-Lin
authors.initials: HL
authors.lastname: Wan
authors.forename: Seik-Weng
authors.initials: SW
authors.lastname: Ng
mesh_terms: D018360:Crystallography, X-Ray; D006016:Glycolates / Q000737:chemistry*; D019344:Lactic Acid / Q000737:chemistry*; D015394:Molecular Structure; D008982:Molybdenum / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D006016:Glycolates; D009942:Organometallic Compounds; C031149:glycolic acid; C044659:molybdate; D019344:Lactic Acid; D008982:Molybdenum