A KINETIC-STUDY ON THE REACTIVITY OF A CIS-DIOXORUTHENIUM(VI) COMPLEX - OXIDATION OF ALCOHOLS, AROMATIC-HYDROCARBONS, AND ALKENES BY CIS-[RU-VI(TET-ME(6))O-2](2+)

The kinetics of oxidation of alcohols, aromatic hydrocarbons, and alkenes by cis-[Ru-VI(Tet-Me(6))O-2](2+) (Tet-Me(6) = N,N,N',N'-tetramethyl-3,6-diazaoctane-1,8-diamine) have been studied. In general, the oxidation chemistry of cis-[Ru-VI(Tet-Me(6))O-2](2+) is similar to those of trans-dioxoruthellium(VI) compounds such as trans-[Ru-VI(N2O2)O-2](2+) (N2O2 = 1,12-dimethyl-3,4:9,10-dibenzo-1,12-diaza-5,8- dioxacyclopentadecane) and trans-[Ru-VI(pytn)O-2](2+) (pytn = N,N'-dimethylbis(2-pyridylmethyl)-propylenediamine). The oxidation is first-order with respect to cis-[Ru-VI(Tet-Me(6))O-2](2+) and organic substrates and is accompanied by large and negative Delta S double dagger. Large k(H)/k(D) values were found for the oxidation of alcohols. A linear Hammett plot for the oxidation of para-substituted benzyl alcohols with a slope of -1.0 was obtained. For alcohol oxidation, a charge-transfer mechanism involving hydride abstraction has been proposed. Oxidation of toluene, ethylbenzene, and cumene by cis[Ru-VI(Tet-Me(6))O-2](2+) gave benzaldehyde, acetophenone/sec-phenylisopropyl alcohol, and 2-phenylisopropyl alcohol, respectively. A k(H)/k(D) value of 11 has been found for the oxidation of ethylbenzene. In the oxidation of these aromatic hydrocarbons, the key step likely involves C-H bond activation in the transition state. Allylic oxidation is the major reaction pathway in the cyclohexene oxidation. In the oxidation of alkenes, both C=C bond cleavage product(s) and epoxides were found. The Hammett plot for the oxidation of para-substituted styrenes is linear with a slope of -2.0. The oxidation likely proceeds through a charge-transfer mechanism.