title: Dimeric dioxomolybdenum(VI) and oxomolybdenum(V) complexes with citrate at very low pH and neutral conditions.
abstract: A novel dimeric dioxomolybdenum(VI) citrate complex, K[(MoO2)2-(OH)(H2cit)2].4H2O (1), with weak coordination of beta-carboxylic acid groups and the first structural example of an oxomolybdenum(V) citrate complex, (NH4)6[Mo2O4(cit)2].3H2O (2) (H4cit = citric acid), are isolated in a very acidic solution (pH 0.5-1.0) and neutral conditions (pH 7.0-8.0), respectively. Complex 1 displays strong double hydrogen bonds through beta-carboxyl and beta-carboxylic acid groups [2.621(9) A]. Transformations of the dimeric molybdenum(VI) citrate show that protonation of a carboxyl group will weaken the coordination of molybdenum(VI) citrate. There are obvious dissociations of molybdenum(VI/V) citrate complexes based on 13C NMR observations in solution.
authors.affiliation: State Key Laboratory for Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, China. zhzhou@xmu.edu.cn
authors.forename: Zhao-Hui
authors.initials: ZH
authors.lastname: Zhou
authors.forename: Yuan-Fu
authors.initials: YF
authors.lastname: Deng
authors.forename: Ze-Xing
authors.initials: ZX
authors.lastname: Cao
authors.forename: Rong-Hua
authors.initials: RH
authors.lastname: Zhang
authors.forename: Yuan L
authors.initials: YL
authors.lastname: Chow
mesh_terms: D002951:Citrates; D019281:Dimerization; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008982:Molybdenum; D009942:Organometallic Compounds / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D002951:Citrates; D009942:Organometallic Compounds; D008982:Molybdenum