1636-01-7Relevant articles and documents
Oxovanadium(v)-catalyzed oxidative cross-coupling of enolates using O2as a terminal oxidant
Osafune, Yuma,Jin, Yuqing,Hirao, Toshikazu,Tobisu, Mamoru,Amaya, Toru
supporting information, p. 11697 - 11700 (2020/10/19)
The oxovanadium(v)-catalyzed oxidative cross-coupling of enolates using O2 as a terminal oxidant is reported, where a boron enolate and a silyl enol ether were employed as enolates. The redox behavior of V(v/iv) in this reaction under O2 was investigated by ESR and 51V NMR experiments.
Vanadium(IV) and -(V) complexes with O,N-chelating aminophenolate and pyridylalkoxide ligands
Hagen, Henk,Bezemer, Chris,Boersma, Jaap,Kooijman, Huub,Lutz, Martin,Spek, Anthony L.,Van Koten, Gerard
, p. 3970 - 3977 (2008/10/08)
Two different monoanionic O,N-chelating ligand systems, i.e., [OC6H2(CH2NMe2)-2-Me2-4,6]- (1) and [OCMe2-([2]-Py)]- (2), have been applied in the synthesis of vanadium(V) complexes. The tertiary amine functionality in 1 caused reduction of the vanadium nucleus to the 4+ oxidation state with either [VOCl3], [V(=NR)Cl3], or [V(=NR)(NEt2)3] (R = Ph, (3a, 5a), R = p-Tol (3b, 5b)), and applying 1 as a reducing agent resulted in the synthesis of the vanadium(IV) complexes [VO(OC6H2(CH2NMe2)-2-Me2-4,6)2] (4) and [V(=NPh)(OC6H2(CH2NMe2)-2-Me2-4,6)2] (6). In the case of [V(=N-p-Tol)(NEt2)(OC6H2(CH2NMe2)-2-Me2-4,6)2] (7b), the reduction was sufficiently slow to allow its characterization by 1H NMR and variable-temperature studies showed it to be a five-coordinate species in solution. Although the reaction of 1 with [V(=N-p-Tol)(O-i-Pr)3] (9b) did not result in reduction of the vanadium nucleus, vanadium(V) compounds could not be isolated. Mixtures of the vanadium-(V) (mono)phenolate, [V(=N-p-Tol)(O-i-Pr)2(OC6H2(CH2NMe2)-2-Me2-4,6)] (10), and the vanadium(V) (bis)phenolate, [V(=N-p-Tol)(O-i-Pr)(OC6H2(CH2NMe2)-2-Me2-4,6)2] (11), were obtained. With the pyridylalkoxide 2, no reduction was observed and the vanadium(V) compounds [VOCl2(OCMe2([2]-Py))] (12) and [V(=N-p-Tol)Cl2(OCMe2([2]-Py)] (13) were obtained. 51V NMR showed 7b and 12 to be five-coordinate in solution, whereas for 10, 11, and 13 a coordination number of 6 was found. Compounds 12 and 13 showed decreased activity compared to their nonchelated vanadium(V) analogues when applied as catalysts in ethene polymerization. Two polymorphic forms with a difference in the V-N-C angle of 12.5°have been found for 6. Crystal data: 6·Et2O, triclinic, P1, a = 11.1557(6) A, b = 12.5744(12) A, c = 13.1051(14) A, α = 64.244(8)°, β = 70.472(7)°, γ = 87.950(6)°, V = 1547(3) A3, Z = 2; 6·C6H6, triclinic, P1, a = 8.6034(3) A, b = 13.3614(4) A, c = 15.1044(5) A, α = 98.182(3)°, β = 105.618(2)°, γ = 107.130(2)°, V = 1551.00(10) A3, Z = 2; 12, orthorhombic, Pbca, a = 11.8576(12) A, b = 12.6710(13) A, c = 14.722(2) A, V= 2211.9(4) A3, Z = 8.
High valence vanadium complex promoted selective rearrangement of epoxides to aldehydes or ketones
Martinez, Fernando,Campo, Carmen del,Llama, Emilio F.
, p. 1749 - 1752 (2008/10/08)
High valence vanadium complexes induce the selective ring opening of epoxides. The monosubstituted epoxides are isomerized with complete regioselectivity each forming a single carbonyl compound exclusively. Likewise a highly regioselective isomerization of 1,1-disubstituted or 1,1,2-trisubstituted epoxides was observed in all reactions.
Synthesis and reactivity of oxovanadium(V) trialkoxides of bulky and chiral alcohols
Crans, Debbie C.,Chen, Haojiang,Felty, Robert A.
, p. 4543 - 4550 (2007/10/02)
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.
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
