Vanadyl acetylacetonate
# Vanadyl acetylacetonate

Vanadyl acetylacetonate is the chemical compound with the formula $VO(acac)_2,$ where $acac^–$ is the conjugate base of acetylacetone. It is a blue-green solid that dissolves in polar organic solvents. The coordination complex consists of the vanadyl group, $VO^{2+},$ bound to two $acac^–$ ligands via the two oxygen atoms on each. Like other charge-neutral acetylacetonate complexes, it is not soluble in water.

## Synthesis

The complex is generally prepared from vanadium(IV), e.g. vanadyl sulfate:

    $VOSO_4$ + 2 Hacac → $VO(acac)_2$ + $H_2SO_4$

It can also be prepared by a redox reaction starting with vanadium pentoxide. In this reaction, some acetylacetone is oxidized to 2,3,4-Pentanetrione.

## Structure and properties

The complex has a square pyramidal structure with a short V=O bond. This $d^1$ compound is paramagnetic. Its optical spectrum exhibits two transitions. It is a weak Lewis acid, forming adducts with pyridine and methylamine.

## Applications

It is used in organic chemistry as a catalyst for the epoxidation of allylic alcohols by tert-butyl hydroperoxide (TBHP). The $VO(acac)_2–TBHP$ system exclusively epoxidizes geraniol at the allylic alcohol position, leaving the other alkene of geraniol untouched. By comparison, m-CPBA, another epoxidizing agent, reacts with both alkenes, creating the products in a two to one ratio favoring reaction at the alkene away from the hydroxyl group. TBHP oxidizes $VO(acac)_2$ to a vanadium(V) species which coordinates the alcohol of the substrate and the hydroperoxide, directing the epoxidation to occur at the alkene close to this coordination site.

## Biomedical aspects

Vanadyl acetylacetonate exhibits insulin mimetic properties, in that it can stimulate the phosphorylation of protein kinase B (PKB/Akt) and glycogen synthase kinase 3 (GSK-3). It has also been shown inhibit tyrosine phosphatase (PTPase), PTPases such as PTP1B, which dephosphorylates insulin receptor beta subunit, thus increasing its phosphorylation, allowing for a prolonged activation of IRS-1, PKB, and GSK-3, allowing them to exert their anti-diabetic properties.

