7681-91-6Relevant articles and documents
Synthesis and characterization of a VO3+ complex of a pentadentate amine alcohol ligand: Towards hydrolytically stable ligands forming model complexes for vanadium-dependent haloperoxidases
Plass, Winfried
, p. 221 - 229 (1996)
The vanadium(V) complex of a hydrolytically stable trivalent, pentadentate amine alcohol ligand has been synthesized by reaction with ammonium meta-vanadate. The ligand was prepared by reduction of the Schiff base precursor N-salicylidene-2-(bis(2-hydroxyethyl)amino)ethylamine and exhibits an enlarged flexibility as compared to its Schiff base analogue. The vanadium(V) complex is characterized by 1H, 13C and 51V NMR, vibrational (IR, Raman and resonance Raman) and electronic spectroscopy. The LMCT transition of the complex has been assigned on the basis of resonance Raman spectroscopy and density functional calculations (LDA). The X-ray crystal structure analysis of C13H19N2O4V (monoclinic, space group C2/c: a = 1948.1(4), b = 1184.9(2), c = 1328.3(2) pm, β = 114.86(1)°, Z = 8) shows that the vanadium(V) center has a distorted octahedral environment with the oxo group in the trans position to the tertiary amine nitrogen. In the solid state racemic pairs of the vanadium(V) complex are formed by hydrogen bridges (N-H ... O). The bond valence sum (BVS) analysis is applied to the complex prepared in this work and compared with the results obtained for a series of more than twenty relevant six-coordinate complexes. In solution a second isomer with the oxo group trans to the secondary amine nitrogen is observed. The ratio of the two isomers varies with the solvent, as was determined by 51V NMR spectroscopy. The methanolysis as well as hydrolysis reaction of the vanadium(V) complex is studied by 51V NMR. The implications of the results for the proposed model of the active site of vanadium-dependent haloperoxidases are discussed.
Ion Chemistry of OV(OCH3)3 in the Gas Phase: Molecular Cations and Anions and Their Primary Fragmentations
Schr?der, Detlef,Loos, Jessica,Engeser, Marianne,Schwarz, Helmut,Jankowiak, Hans-Christian,Berger, Robert,Thissen, Roland,Dutuit, Odile,D?bler, Jens,Sauer, Joachim
, p. 1976 - 1985 (2004)
Trimethyl vanadate(V), OV(OCH3)3 (1), is examined by various mass spectrometric means. Photoionization experiments yield an ionization energy of IE(OV(OCH3)3) = 9.54 ± 0.05 eV for the neutral molecule. The primary fragmentation of the molecular cation 1+, i.e., loss of neutral formaldehyde, can occur via two independent routes of hydrogen migrations to afford the formal VIV compounds HOV(OCH3)2+ and OV(OCH 3)(CH3OH)+, respectively. These two pathways are associated with low-lying activation barriers of almost identical height. At elevated energies, direct V-O bond cleavage of 1+ allows for expulsion of a methoxy radical concomitant with the generation of the cationic fragment OV(OCH3)2+, a formal VV compound. Trimethyl vanadate can also form a molecular anion, 1-, whose most abundant dissociation channel involves loss of a methyl radical, thereby leading to the formal VV compound OV(OCH3) 2O-. Various mass spectrometric experiments and extensive theoretical studies provide detailed insight into the ion structures and the relative energetics of the primary dissociation reactions of the molecular cations and anions of 1.
A Mixed-Valence VIV/Valkoxo-polyoxovanadium cluster series [V6O8(OCH3)11] n+l-: Exploring the Influence of a μ-Oxo ligand in a spin frustrated structure
Daniel, Charles,Hartl, Hans
, p. 5101 - 5114 (2009/09/30)
The synthesis and structural characterization of the neutral mixed-valence methoxo-polyoxovanadium cluster [V 6 O 8 (OCH 3 ) 11 ] (1) and its single oxidation product in the hexachloroantimonate salt [V 6 O 8 (OCH 3 ) 11 ][SbCl 6 ] (2) are presented here. The cluster comprisesa hexauclear polyoxovanadate core of the Lindqvist structure, of which all but one of the μ-bridging oxo ligands are substituted by methoxo. As revealed by cyclic voltammetry, the cluster is highly redox active, displaying several further thermodynamically stable V IV /VV mixed-valence redox derivatives. Furthermore, valence sum calculations performed on the X-ray structural data as well as results from IR and UV-vis spectrometry characterize them as class II mixed-valence compounds. In the present article, we equally present results from cyclic voltammetry, UV-vis spectrometry, and magnetic measurements obtained formembers of the previously reported [V 6 O 7 (OCH3 ) 12 ] - cluster series, which, as opposed to1 and its derivatives, contain exclusively methoxo ligands as μ-brid ging moieties. Magnetic measurements performed on the highly reduced cluster species [V IV 5 VV 1 O 7 (OCH 3 ) 12 ] - and [V IV 6 VVO 7 (OCH 3 ) 12 ] 2- reveal net antiferromagnetic exchange interactions between the d-electrons, which at lower temperatures are in part suppressed for reasons attributed to geometric spin frustration. Among the present results, the comparison of the cyclic voltammograms of 1 and [V 6 O 7 (OCH 3 ) 12 ] has proven to be of considerable interest, showing an unexpectedly pronounced discrepancy in all but one of their corresponding redox potentials. In particular, a detailed analysis of the electrochemical conversions indicates that the observed shift is almost entirely the result of a different degree of d-electron spin-spin interactions in corresponding mixed valence species of the cluster series.
Mono- and dinuclear oxovanadium(V)calixarene complexes and their activity as oxidation catalysts
Hoppe, Elke,Limberg, Christian,Ziemer, Burkhard
, p. 8308 - 8317 (2008/10/09)
The background of the investigation is constituted by reactive moieties and intermediates playing relevant roles on the surfaces of vanadiumoxide-based catalysts during the oxygenation/dehydrogenation of organic substrates. With the aim of modeling such species, a series of mono- and dinuclear charged and uncharged vanadium oxo complexes containing p-tert-butylated calix[4]arene and calix[8]arene ligands (denoted H4B and H8B″, respectively, in the protonated forms) has been synthesized and characterized: PPh4[O=VB] (PPh41), O=VBOAc (2), PPh 4[O2V2HB″] (3), and [μ-O(O=V(OMe)) 2BMe2] (4), where superscripts OAc and Me2 indicate that one or two protons of H4B are substituted by these residues, respectively. These compounds were analyzed both in solution and by means of single-crystal X-ray crystallography; it turned out that the crystal structures are retained on dissolution (2 changed only from the paco to the cone structure). In the case of 4, it could be shown that the bulk product consists of a mixture of two isomers (4t and 4c) differing in the relative positions of the vanadium-bound methoxy groups. Subsequently, all compounds were tested as catalysts for the oxidation of alcohols with O 2. It turned out that the two dinuclear complexes efficiently catalyze the oxidation of 1-phenyl-1-propargyl alcohol and fluorenol; in addition, they even show some activity with respect to the oxidation of dihydroanthracene. This may hint to a higher activity of dinuclear sites on the surfaces of heterogeneous catalysts as well.
Binding of L-histidine to vanadium. Structure of exo-[VO2{N-(2-oxidonaphthal)-His}]
Vergopoulos, Vassilios,Priebsch, Wolfgang,Fritzsche, Martina,Rehder, Dieter
, p. 1844 - 1849 (2008/10/08)
The VIV complexes VO(H2O)L (2) (H2L is a Schiff base derived from o-hydroxynaphthalenecarbaldehyde and the amino acids glycine or phenylalanine) react with amines under aerobic conditions to VV complexes of the general composition VO(OH)L(amine) (5) (amine = imidazole, methylimidazole, pyrrole, pyridine, histidine, and histidine derivatives). With alcohols, the complexes VO(OR)L(ROH) (6) are formed. Histidine can also replace glycine in 2, forming the title compound 3 with the histidine moiety coordinating through one of the carboxylate-O moieties. Crystallographic data for 3: [VO2{O2CCH(CH2C3H4N 2)N=CHC10H6O}], space group C2; Z = 4, a = 13.7077(17) ?, b = 6.7390(6) ?; c= 17.1851(15) ?, β = 95.644(8)°, V = 1579.8(3) ?3, R = 0.0325, Rw = 0.0358, 3011 reflections (2916 with I > 2σ(I). The geometry around vanadium is square pyramidal. The two nitrogens of the imidazole unit are linked by intermolecular hydrogen bonds to the carboxylate oxygens and to the oxo group in the tetragonal plane. 3 models several of the active site features for vanadate-dependent haloperoxidases from marine brown algae.
Synthesis and Properties of tert-Butyliminovanadium(V) Compounds tC4H9N=VX3 (X = Br, OR)
Preuss, Fritz,Towae, Willi,Kruppa, Volker,Fuchslocher, Edith
, p. 1510 - 1517 (2007/10/02)
tC4H9N=VBr3 has been prepared by reaction of the trichloride with hydrogen bromide dissolved in benzene.The structure of the 2,2'-dipyridyl complex tC4H9N=VBr3*C10H8N2> has been found to be octahedral with meridional arrangement of bromide.Syntheses of tC4H9N=V(OR)3 and iC3H7N=V(OR)3 are described.The properties of these compounds are studied by chemical reactions such as redistribution, transamination and alcoholysis.The 51V NMR spectra of the alkyliminovanadium(V) compounds are discussed; the constants of 51V, 14N coupling have been determined.The oxovanadium(V) complex has been prepared; all attempts to prepare VO(OCH3)2Cl have not been successful. - Key words: tert-Butyliminovanadium(V) Tribromide, Tris(alkoxo)alkyliminovanadium(V), 51V NMR Spectra
