Interaction of Catechol and Catechol Derivatives with Dioxovanadium:(V). I. Kinetics of Complex Formation in Acidic Media

Abstract

g,.0.264 mmol) was placed in the bottom of a quartz hot tube. The tube was packed with ceramic saddles and sublimer maintained at -78°was attached. A high vacuum was applied and the hot tube was heated to 650°. The solid was then sublimed up the hot tube by heating with a silicone oil bath between 250 and 290°. Thirty milliliters of silica gel was added to the sublimate which was dissolved in methylene chloride. The solvent was removed on a rotary evaporator, and the solids were mounted on a column of silica gel (600 ml dry volume) in hexane. The column was then eluted with hexane gradually enriched with methylene chloride giving eight fractions identified as orange 4,10,1,7-(C5H5)2Co2C2B8Hio (XI) (105 mg, 0.029 mmol, 11%), orange 2,8,1,12-(C5H5)2Co2C2BsHio (XII) (90 mg, 0.0238 mmol, 9%), 4,12,1,7-(CsH5)2Co2C2B8Hio (XIII) (10 mg, 0.0026 mmol, 1.0%), red 2,10,1,7-(CsHshO^BgHm (XIV) (28 mg, 0.093 mmol, 3%), purplish 2,9,1,12-(C5H5)2Co2C2B8Hio (XV) (10 mg, 0.0026 mmol, 1%), orange 2,5,1,7-(C5H5)2Co2C2B8Hio (XVI) (9 mg, 0.0024 mmol, 0.9%), orange 2,4,1,7-(C5H5)2Co2C2B8H,0 (X) (15 mg, 396 mmol, 1.5%), and red 3,6,1,2-(C5H5)2Co2C2B8Hi0 (IX) (70 mg, 0.0185 mmol, 7%).

Mechanism of Dioxovanadium Ion Reduction on Oxygen-Enriched Carbon Surface

“…Due to the low possibility of the physical adsorption by a weak Van der Waals interaction between ions and carbon surface, it is reasonable to assume that the vanadium ion species were coordinated by the oxygen-functional groups on the GC surface and retained as the chemical adsorption. 17 There are a few reports on the XPS measurements for vanadium species on carbon materials; only the XPS …”

The Chemistry and Biochemistry of Vanadium and the Biological Activities Exerted by Vanadium Compounds

“…Some of these complexes contain no oxo groups, and although nonoxo complexes are relatively rare for complexes with vanadium in oxidation state IV and V, they predominate in complexes of V(III). 577 Fundamental studies of the reaction of V(V) with the simple catechols and substituted catechols are crucial for a detailed understanding of this rich redox chemistry 568,570,[578][579][580] and have been reviewed. 246,250,540,581,582 V(V) catechol complexes have been reported in solution 578,579 and in the solid state.…”

Vanadium: Global (bio)geochemistry

“…It is known that vanadate oxyanions form relatively weak complexes with organic compounds, as compared to the V(IV) oxycation VO 2+ (Wehrli, 1987). Nevertheless, V(V)-organic complexes have been suggested as the essential intermediates for the reduction of V(V) (Kustin et al, 1974;Wells and Kuritsyn, 1970), and V is known to be stabilized against reduction by binding to humic substance at circumneutral pH values (Lu et al, 1998). The strong tendency of V(IV) to form stable complexes helps explain the presence of V(IV) in natural waters under oxic conditions (Wehrli, 1987).…”