title: Formations of mixed-valence oxovanadiumV,IV citrates and homocitrate with N-heterocycle chelated ligand.
abstract: Dimeric mixed-valence oxovanadium citrate [V 2O 3(phen) 3(Hcit)].5H 2O ( 1) (H 4cit = citric acid, phen = 1,10-phenanthroline) was isolated from a weak acidic medium. It could be converted quantitatively into a tetrameric oxovanadium citrate adduct of 1,10-phenanthroline [V 2O 3(phen) 3(Hcit) 2(phen) 3O 3V 2].12H 2O ( 2). This was supported by the trace of infrared spectra and X-ray diffraction patterns. The two compounds feature a bidentate citrate group that chelates only to one vanadium center through their negatively charged alpha-alkoxy and alpha-carboxy oxygen atoms, while the other beta-carboxy and beta-carboxylic acid groups are free to participate in strong intramolecular and intermolecular hydrogen bonding [2.45(1) in 1 and 2.487(2) A in 2], respectively. This is also the case of homocitrato vanadate(V/IV) [V 2O 3(phen) 3( R, S-H 2homocit)]Cl.6H 2O ( 3) (H 4homocit = homocitric acid), which features a binding mode similar to that found in the R-homocitrato iron molybdenum cofactor of Mo-nitrogenase. Moreover, the homocitrato vanadate(V) [VO 2(phen) 2] 2[V 2O 4( R,S-H 2homocit) 2].4H 2O.2C 2H 5OH ( 4) is isolated as a molecular precursor for the formation of mixed-valence complex 3. The V-O alpha-alkoxy and V-O alpha-carboxy bond distances of homocitrate complexes 3 and 4 are 1.858(4) and 1.968(6) av and 2.085(4) and 1.937(5) A, respectively. They are shorter than those of homocitrate to FeVco (2.15 A). The gamma-carboxy groups of coordinated homocitrato complexes 3 and 4, and the free homocitrate salt Na 3(Hhomocit).H 2O ( 5), form strong hydrogen bonds with the chloride ion and the water molecule [2.982(5) in 3, 2.562(9) in 4, and 2.763(1) A in 5], respectively.
authors: State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
authors: Can-Yu
authors: CY
authors: Chen
authors: Zhao-Hui
authors: ZH
authors: Zhou
authors: Hong-Bin
authors: HB
authors: Chen
authors: Pei-Qiang
authors: PQ
authors: Huang
authors: Khi-Rui
authors: KR
authors: Tsai
authors: Yuan L
authors: YL
authors: Chow
mesh_terms: D002614:Chelating Agents / Q000737:chemistry*; D002951:Citrates / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D008024:Ligands; D009584:Nitrogen / Q000737:chemistry*; D014233:Tricarboxylic Acids / Q000737:chemistry*; D014638:Vanadates / Q000737:chemistry*
chemical_list: D002614:Chelating Agents; D002951:Citrates; D006571:Heterocyclic Compounds; D008024:Ligands; D014233:Tricarboxylic Acids; C075743:oxovanadium IV; C028143:homocitric acid; D014638:Vanadates; D009584:Nitrogen