Vanadium(V) Hydroxylamido Complexes: Solid State and Solution Properties
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- 作者：Anastasios D. Keramidas ; Susie M. Miller ; Oren P. Anderson ; and Debbie C. Crans
- 刊名：Journal of the American Chemical Society
- 出版年：1997
- 出版时间：September 24, 1997
- 年：1997
- 卷：119
- 期：38
- 页码：8901 - 8915
- 全文大小：278K
- 年卷期：v.119,no.38(September 24, 1997)
- ISSN：1520-5126
文摘
A novel series of vanadium(V) hydroxylamido complexes withweak ligands including glycine, [VO(NH2O)2(Glycine)]·H2O(1); serine,[VO(NH2O)2(Serine)]·H2O(2); glycylglycine,[VO(NH2O)2(GlyGly)]·H2O(3);and imidazole,[VO(NH2O)2(imidazole)2]Cl(4) were prepared and characterized both in solution and inthe solidstate. All complexes were prepared in aqueous solution at neutralpH at ambient temperature and as crystallinesolids. The vanadium atom in these four complexes isseven-coordinate with pentagonal bipyramidal geometry.Incomplexes 1-3 the hydroxylamidogroups are coordinated side-on with the hydroxylamido nitrogen cis tothe organicligand in the equatorial plane. In complex 4, thehydroxylamido groups are coordinated side-on with thehydroxylamidonitrogen trans to the imidazole ligand in the equatorial plane.The UV/vis spectra of these complexes were alsoexamined, and the absorbance peaks show similarities between theproperties of the vanadium(V) hydroxylamidocomplexes and known side-on peroxovanadium complexes. MultinuclearNMR studies were conducted to characterizethe solution structure and properties of compounds1-4. A particularly detailedstudy of compound 4 was carriedout since the analogous vanadium(V) peroxo complex could also beprepared. Complex 4 was less labile andmorestable than the corresponding diperoxovanadium(V)-imidazolecomplex, H[VO(O2)2(imidazole)](5). In solutionthe inherent asymmetry of the hydroxylamido ligand has facilitated anin-depth study of ligand exchange. Upondissolution, compound 4 forms three isomeric complexes, allof which have one of the original two-coordinatedimidazole groups in the complex dissociated. 1D and 2D EXSY andmultinuclear NMR spectroscopies were usedto examine the stoichiometry of the isomers, their structures, and thedynamics of their ligand exchanges. Specifically,both inter- and intramolecular exchanges were observed for thedihydroxylamine-vanadium(V)-imidazole involvingboth the coordinated imidazole and the coordinated hydroxylamidogroups. The intramolecular exchange of thecoordinated imidazole in 5 was compared to the exchange inthe hydroxylamido complex, and the hydroxylamidocompounds were found to have some properties that may be advantageousover those of the diperoxovanadium(V)complexes. In summary, evidence was generated to support theexistence of a novel and unprecedented asymmetrichydroxylamido-metal complex as well as the first isolation andcharacterization of a vanadium(V)-imidazole complexnot enjoying stabilization by other organic ligands.