A series of room temperature ionic liquids (RTILs) were tested as solvents for dioxomolybdenum(VI) complexes in the catalytic epoxidation of cis-cyclooctene, using tert-butyl hydroperoxide (TBHP) as the mono-oxygen source. In general, the best results were obtained using the RTIL 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM]NTf2). Upon addition of cyclooctene and TBHP (in decane) to solutions of MoO2X2(p-toyl-(CH3-DAB)) [X = Cl, Me; p-tolyl-(CH3-DAB) = N,N-p-tolyl-2,3-dimethyl-1,4-diazabutadiene] in [BMIM]NTf2, biphasic mixtures were obtained. The epoxidation reactions proceeded with 100% selectivity to cyclooctene oxide, but activities were lower than those observed for the same catalysts in the absence of any additional solvent (other than decane). By contrast, in the presence of the novel cationic complex [MoO2Cl(Bn3Me3-tame)]BF4 [Bn3Me3-tame = N,N',N-tribenzyl-1,1,1-tris(methylaminomethyl)ethane] and [BMIM]NTf2, the catalytic activity was higher than that achieved with no