Vanadyl acetylacetonate
Encyclopedia
Vanadyl acetylacetonate is the chemical compound
with the formula
VO(C5H7O2)2. This blue-green coordination complex
consists of the vanadyl
group, VO2+, bound to two acetylacetonate
anions, acac−. Like other charge-neutral acetylacetonates, this complex is soluble in organic solvents.
The compound is recrystallized from chloroform.
s with pyridine
and methylamine
.
as a reagent in the epoxidation of allyl
ic alcohol
s in combination with tert-butyl hydroperoxide
(TBHP). The VO(acac)2-TBHP system exclusively epoxidizes geraniol
at the allylic alcohol position. For comparison, another epoxidizing agent m-CPBA, reacts with both groups, creating the products in a two to one ratio, favoring the allylic position away from the alcohol. TBHP oxidizes VO(acac)2 to a vanadium(V)
species which coordinates the alcohol
of the substrate
and the hydroperoxide.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
VO(C5H7O2)2. This blue-green coordination complex
Complex (chemistry)
In chemistry, a coordination complex or metal complex, is an atom or ion , bonded to a surrounding array of molecules or anions, that are in turn known as ligands or complexing agents...
consists of the vanadyl
Vanadyl ion
The vanadyl or oxovanadium cation, [VO]2+, is a blue-coloured vanadium oxocation. It is one of the most stable diatomic ions known and forms a wide range of complexes.-Compounds containing the vanadyl ion:* vanadyl, VO2...
group, VO2+, bound to two acetylacetonate
Acetylacetone
Acetylacetone is an organic compound that famously exists in two tautomeric forms that rapidly interconvert. The less stable tautomer is a diketone formally named pentane-2,4-dione. The more common tautomer is the enol form. The pair of tautomers rapidly interconvert and are treated as a single...
anions, acac−. Like other charge-neutral acetylacetonates, this complex is soluble in organic solvents.
Synthesis
The complex is prepared from vanadium(IV), e.g. vanadyl sulfate, or vanadium(V) precursors, such as vanadium pentoxide. The equation for the redox reaction starting from the pentoxide can be described by this approximate equation:- 2 V2O5Vanadium(V) oxideVanadium oxide is the chemical compound with the formula V2O5. Commonly known as vanadium pentoxide, this brown/yellow solid is the most stable and common compound of vanadium. Upon heating it reversibly loses oxygen...
+ 9 C5H8O2 → 4 VO(C5H7O2)2 + (CH3CO)2CO + 5 H2O
The compound is recrystallized from chloroform.
Structure and properties
The complex has a square pyramidal structure with a short V=O bond. This d1 compound is paramagnetic. Its optical spectrum exhibits two transitions. It is a weak Lewis acid, forming adductAdduct
An adduct is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is considered a distinct molecular species...
s with pyridine
Pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...
and methylamine
Methylamine
Methylamine is the organic compound with a formula of CH3NH2. This colourless gas is a derivative of ammonia, but with one H atom replaced by a methyl group. It is the simplest primary amine. It is sold as a solution in methanol, ethanol, THF, and water, or as the anhydrous gas in pressurized...
.
Applications
It is used in organic chemistryOrganic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
as a reagent in the epoxidation of allyl
Allyl
An allyl group is a substituent with the structural formula H2C=CH-CH2R, where R is the connection to the rest of the molecule. It is made up of a methylene , attached to a vinyl group . The name is derived from the Latin word for garlic, Allium sativum. Theodor Wertheim isolated an allyl...
ic alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s in combination with tert-butyl hydroperoxide
Tert-Butyl hydroperoxide
tert-Butyl hydroperoxide is an organic peroxide widely used in a variety of oxidation processes, for example Sharpless epoxidation...
(TBHP). The VO(acac)2-TBHP system exclusively epoxidizes geraniol
Geraniol
Geraniol is a monoterpenoid and an alcohol. It is the primary part of rose oil, palmarosa oil, and citronella oil . It also occurs in small quantities in geranium, lemon, and many other essential oils. It appears as a clear to pale-yellow oil that is insoluble in water, but soluble in most common...
at the allylic alcohol position. For comparison, another epoxidizing agent m-CPBA, reacts with both groups, creating the products in a two to one ratio, favoring the allylic position away from the alcohol. TBHP oxidizes VO(acac)2 to a vanadium(V)
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
species which coordinates the alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
of the substrate
Substrate (chemistry)
In chemistry, a substrate is the chemical species being observed, which reacts with a reagent. This term is highly context-dependent. In particular, in biochemistry, an enzyme substrate is the material upon which an enzyme acts....
and the hydroperoxide.