collected and stored in a sealed sample vial. The product was
characterized by infrared (IR) spectroscopy.
For the oxidation reactions, VO(acac)2 and anthracene were
placed in a round-bottom flask and dissolved in ethyl acetate
(Scheme 1). To this was added hydrogen peroxide and the
reaction was allowed to proceed at the desired temperature for 2
h. When the reaction was done, water was added and the organic
layer removed. The water layer was then extracted with chloroform
or dichloromethane and the organic solution was combined
with the ethyl acetate. The organic solvents were evaporated to
isolate the solid product, which was then washed with toluene
and allowed to dry. The product was collected, weighed, and then
analyzed by thin-layer chromatography (TLC) using standard
samples of anthracene and anthraquinone, running three spots
side by side on the same plate. An ultraviolet (UV) lamp was used
to visualize the spots on the TLC plate. If the product was not
pure, further washings with toluene were performed until the
TLC showed pure product.
The capacity for the 5-coordinate structure to accommodate an
additional ligand can be demonstrated by dissolving the compound
in coordinating solvents such as pyridine or solutions
containing aqueous ammonia or sodium carbonate. Coordination
of a sixth ligand changes the color compared to solutions in
noncoordinating solvents such as chloroform or dichloromethane.
Given the workup that we use, the catalyst is not easily
collected and recycled