Ž .
Ž . Monomeric and oligomeric vanadium V species the latter obtained by acid-induced aggregation are mostly anionic, and can be solubilized in non-polar solvents by cationic phase-transfer catalysts. Monomeric and cyclic tetra-and Ž . pentavanadate form 1:1 ion-pair complexes with Aliquat 336 ALCl . The ion-pairs of decavanadates have the compositions w x w Ž .x ALCl r V V 1:0.3-0.5, due to the formation of differently protonated species at lower pHs. Both ALCl and the ion-pair org Ž . complex AL-V V influence the rate of decomposition of t-butylhydroperoxide and the rates of oxidation of hydrocarbons by O . Pure ALCl is more active at pH ) 7 than at pH -7, in consequence of the transformation of ALCl into ALOH in 2 Ž . alkaline medium. In contrast, the ion-pair complex AL-V V is hardly active at pH ) 7, due to the low or zero activity of Ž . Ž . monomeric V V . The activities of ion-pairs containing oligomeric V V species exceed that of ALCl alone. It was observed Ž . that the activities of both ALCl and the ion-pair complex AL-V V depend almost linearly on their concentration, but when Ž . an upper limit about 0.1 M is exceeded, the catalytic activity suddenly drops to a low value.