Unveiling of a Trinuclear Cyclic Peroxidovanadate: A Potential Oxidant in Vanadium-Catalyzed Reactions

The
first peroxidovanadium trimer was prepared in the form of its
tetrabutylammonium salt, (NBu4)3[V3O3(O2)6]·2H2O. Its
X-ray structure analysis revealed a unique cyclic structure of the
[V3O3(O2)6]3– ion incorporating the yet unobserved μ3-η2:η1:η1 coordination mode
of one of its peroxido ligands. While relatively stable in nonaqueous
solvents, the [V3O3(O2)6]3– ion quickly decomposes in diluted aqueous solutions.
A higher vanadium concentration or a higher CH3CN content
in the mixed CH3CN/H2O solvent facilitates the
formation of oligomers [V2O2(O2)4(H2O)]2– and [V3O3(O2)6]3–. 51V NMR investigations indicated that the trinuclear species is incorporated
in vanadium-catalyzed oxidations in the presence of H2O2.