1636-00-6Relevant articles and documents
Synthesis and reactivity of oxovanadium(V) trialkoxides of bulky and chiral alcohols
Crans, Debbie C.,Chen, Haojiang,Felty, Robert A.
, p. 4543 - 4550 (1992)
The synthesis and reactivity of a series of stable oxovanadium(V) trialkoxides is reported of alcohols including exo-norborneol, endo-norborneol, 1-adamantanol, 2-adamantanol, (1R)-endo-(+)-borneol, (1S)-endo-(-)-borneol, and triphenylmethanol. The enantiomerically pure oxovanadium(V) trialkoxides, either all (+) or all (-), are significantly more stable than mixed oxovanadium(V) trialkoxides [(+, +, -) or (-, -, +)]. The reaction between VO(OR)Cl2 and alcohol to form VO(OR)2Cl and HCl was demonstrated to be reversible. The hydrolysis of the oxovanadium(V) trialkoxides was studied in organic solvents using 51V NMR spectroscopy. In organic solvents a mixture of oxovanadium(V) trialkoxide and H2O is more stable than the corresponding dialkoxide hydroxide and alcohol. It appears that oxovanadium(V) trialkoxides are not inherently unstable as has been suggested by aqueous studies. The redox chemistry of oxovanadium(V) alkoxides was explored, and the derivatives were surprisingly resistant to reduction; reducing reagents such as ascorbic acid and 2-mercaptoethanol were required to reduce the vanadium(V). The unusual stability of these new oxovanadium alkoxides suggests that other derivatives with specific properties can be obtained for structural characterization or use in organic synthesis.
Multidentate lewis acids. Adducts of monodentate and bidentate vanadyl dichloride alkoxides with ketones
Viet, Minh Tan Phan,Sharma, Vijay,Wuest, James D.
, p. 3026 - 3032 (2008/10/08)
Combined use of 1H, 13C, and 51V NMR spectroscopy shows that the interaction of VOCl3 with 2 equiv of a ketone in solution at low temperatures produces complex mixtures of neutral and ionic adducts. In contrast, vanadium dichloride isopropoxide (4) forms neutral 1:2 adducts under similar conditions. These adducts are presumably octahedral, with ketones trans to the oxo and alkoxy oxygens. Bound and free ketones exchange by dissociation with free energies of activation near 7 kcal/mol. Analysis of the temperature dependence of the 51V chemical shift of mixtures of compound 4 and excess pinacolone gives ΔH = -10.9 kcal/mol and ΔS = -51 eu for the formation of the 1:2 adduct. At low temperatures, solutions of compound 4 containing 1 equiv of a ketone consist primarily of a 1:1 mixture of free compound 4 and the neutral 1:2 adduct. Vanadyl dichloride alkoxide 6, a bidentate Lewis acid, behaves similarly, and solutions containing 1 equiv of a ketone consist largely of free compound 6 and its unsymmetric 1:2 adduct 8. Significant amounts of symmetric 1:1 adduct 9 with a cooperatively bound carbonyl ligand are not formed, and no other unusual chemical effects can be attributed to the special juxtaposition of electrophilic sites in bidentate Lewis acid 6.
Functionalized Oxovanadium Alkoxides - Potential Haptens
Hillerns, Frank,Rehder, Dieter
, p. 2249 - 2254 (2007/10/02)
Several new oxovanadium alkoxides and alkoxides/chlorides of the composition VOCl3-n(OR)n (n = CPh3; n = 2 and 3, R = CPh3, iBu, cyclopentyl, tert-pentyl, octyl; n 3, R = dodecyl, 3-methylbutyl) and the mixed ester VO(OiBu)-(OCPh3)2 have been prepared.The compounds VO(OiBu)2OR' have ben synthesized, where R' is a functionalized long-chain alkyl group .The chloride/carboxylate VOCl2 has also been obtained.The compounds are characterized, inter alia, by 51V-NMR spectroscopy.Typical 51V shift ranges are observed for specific ligand functionalities (chlorides, alkoxide, carboxylate). δ(51V) values also depend on the steric requirement of the groups R and the coordination number.The importance of the functionalized esters as potential triggers for the production of abzymes with phosphatase activity is discussed.Key Words: Vanadium Alkoxides / Haptens / NMR, 51V
