Vanadium complexes acetylacetonates

Valinomycin metal complexes, 969 Vanadium complexes acetylacetone exchange reactions, 380 1,4-diaza-l,3-butadiene, 209 dioxygen mononuclear, 321 hydrazido(2-), 148 hydroxamic adds, 506 phthalocyanines, 865 polypyrazolylborates, 248 porphyrins, 824 dioxygen adducts, 325... 

Vanadium complexes, 3,453-569 acetylacetone exchange reactions, 2,380 alkyl peroxides... 

We studied the oxidation of cyclohexene at 70°C in the presence of cyclopentadienylcarbonyl complexes of several transition metals. As with the acetylacetonates, the metal center was the determining factor in the product distribution. The decomposition of cyclohexenyl hydroperoxide by the metal complexes in cyclohexene gave insight into the nature of the reaction. With iron and molybdenum complexes the product profile from hydroperoxide decomposition paralleled that observed in olefin oxidation. When vanadium complexes were used, this was not the case. Variance in product distribution between the cyclopentadienylcarbonyl metal-promoted oxidations as a function of the metal center were more pronounced than with the acetylacetonates. Results are summarized in Table V. 

An investigation of the kinetics of the decomposition of cyclohexyl hydroperoxide at 60-70 in the presence of vanadyl acetylacetonate was recently carried out [355]. Cyclohexanol and cyclohexanone were formed in roughly a 1 1 ratio. The initial rate of decomposition was first order in initial concentrations of hydroperoxide and vanadium complex at [ROOM] <5 x 10 M and [VO(acac)2] < 1 x 10" M. The initial rate of decomposition changed from first order in [ROOH] to zero order giving evidence of complex formation prior to hydroperoxide decomposition. Using a chemiluminescence method the authors [355] concluded that only about 20% of the cyclohexyl hydroperoxide which decomposed gave free radicals. 

R spectra, 2, 511 Vanadium tetramethoxide spectroscopy, 2, 347 Vanadyl acetylacetonate, 2, 388 hydrolysis, 2, 379 Vanadyl complexes cupferron... 

Vanadium(IV) Schiffsbase complexes derived from P-aminoalcohols 7.62 and vanadyl acetylacetonate have been used to oxidize different substrates to chiral sulfoxides. 

Epoxidation of allyhc and homoallylic alcohols not part of the diene complex can be achieved using the Sharpless r-butyl hydroperoxide/vanadium acetylacetonate protocol. Dihydroxylation of alkenes adjacent to the diene complex using osmium tetraoxide-r-butyl peroxide has been reported... 

Vanadium(III) is reported to form neutral, cationic, anionic and oxo-bridged complexes. The vanadium ion is in a distorted octahedral environment with an O-V-0 bite angle in the acetylacetonate chelate ring moiety of 88.37(9)°. The hexacoordinated V(ni) complexes with o-phenantroline and acetylacetonate show intense IR peaks at 1521 and 1526 cm" that correspond to the v(CO) stretching vibration of planar acac ligands. Substitution of the acac ligand with phenantroline or another slim ligand will allow the approach of another atom for coordination with vanadium, which will become... 

Epoxides undergo deoxygenation upon treatment with vanadium or molybdenum acetylacetonate complexes, although their stereoselectivity is low. When the molybdenum(VI) oxo complex MoO(S2CNEt2)2 is employed, the deoxygenation proceeds with retention of configuration. For example, cw-2-butene oxide is converted to c -2-butene at 130 C in 83% yield. ... 

Apart from the compounds already mentioned, vanadium, manganese, and cobalt chlorides, tetra-alkoxy derivatives of titanium, acetylacetonates of V, Cr, Mo, Mn, and Ni, Cp derivatives of Zr and Nb, and triphenyl phosphine complexes of Ti and Fe were found to be active. Later lanthanide complexes were included in the list of dinitrogen-reducing systems, the most effective being compounds of samarium and yttrium. 

The reaction of vanadium (III) V(acac)3 acetylacetonate with free diAMsar ligand in aqueous ethanol at 40°C for three days led to the formation of a vanadium(IV) [V(diAMHsar-2H)](S206)2 2H20 sarcophaginate. The central ion presumably was oxidized by air oxygen. The isolated complex is stable over a wide pH range (1-10) but decomposes in the presence of oxidants [167]. 

Control of Chemoselectivity. The reaction of allylic alcohols with r-butyl hydroperoxide and vanadium acetylacetonate or titanium tetraisopropoxide provides a highly chemoselective method for the preparation of epoxides, as exemplified below. Catalysis by vanadium is envisioned to involve a complex of r-BuOOH, the OH group of the allylic alcohol, and the metal. 

Parent and derivatized vanadium(V)-tacn complexes (tacn= 1,4,7-triazacyclononane) have been prepared and structurally characterized.435 Various auxiliary ligands have been used including acetylacetonate (acac), isothiocyanate ( NCS), azide, and benzoic acid.436 The acac derivative was used in the synthesis of a nitridovanadium(V) complex (80).436... 

The most direct way to prepare VO(acac)2 is by the reaction of vanadyl sulfate with a source of the ligand. Vanadium(V), such as V205, can be reduced to vanadium(IV) by ethanol solvent in the presence of sulfuric acid. Reaction with acetylacetone in sodium carbonate yields the desired product. The synthesis we will use produces the complex in high yield directly in a system that can visually shed light on the active catalyst species in the epoxidation of olefins, Figure 9.4. 

New scorpionate oxovanadium complexes Syntheses and crystal structures of a series of vanadium(V) complexes with mixed ligands of poly(pyrazolyl)borates and substituted acetylacetonates i i n)9y N O R R = Me, Et 82... 

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