A kinetic study on the reactivity of a cis-dioxoruthenium(VI) complex. Oxidation of alcohols, aromatic hydrocarbons, and alkenes by cis-[Ru{sup VI}(Tet-Me{sub 6})O{sub 2}]2{sup +}
- Univ. of Hong Kong (Hong Kong); and others
The kinetics of oxidation of alcohols, aromatic hydrocarbons, and alkenes by cis-[Ru{sup VI}(Tet-Me{sub 5})O{sub 2}]2{sup +} (Tet-Me{sub 6}=N,N,N`,N`-tetramethyl 3-6-diazaoctane-1,8-diamine) have been studied. In general the oxidation chemistry of cis-[Ru{sup VI}(Tet-Me{sub 5})O{sub 2}]2{sup +} is similiar to those of trans-dioxoruthenium(VI) compounds such as trans-[Ru{sup VI}(N{sub 2}O{sub 2})O{sub 2}]{sup 2+} (N{sub 2}O{sub 2}=1,12-dimethyl-3,4:9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane) and trans-[Ru{sup VI}(pytn)O{sub 2}]{sup 2+} (pytn=N,N`-dimethylbis(2-pyridylmethyl)-propylenediamine). The oxidation is first-order with respect to cis-[Ru{sup VI}(Tet-Me{sub 6})O{sub 2}]{sup 2+} and organic substrates and is accompanied by large and negative {Delta}S. Large kH/kD 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{sup VI}(Tet-Me{sub 6})O{sub 2}]{sup 2+} gave benzaldehyde, acetophone/sec-phenylisopropyl alcohol, and 2-phenylisopropyl alcohol, respectively. A kH/kD value of 11 has been found for the oxidation of ethylbenzene. In the oxidation of the aromatic hydrocarbons, the key step likely involves C-H bond activation in the transition state. Allylic oxidation is the major reaction pathway in the cyclohexane oxidation. In the oxidation of alkenes C=C bond cleavage product(s) and epoxides were found. The Hammett plot for the oxidation of para-substituted styrenes in linear with a slope of -2.0. The oxidation likely proceeds through a charge-transfer mechanism. 28 refs., 4 figs., 7 tabs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 274005
- Journal Information:
- Journal of Organic Chemistry, Vol. 60, Issue 21; Other Information: PBD: 20 Oct 1995
- Country of Publication:
- United States
- Language:
- English
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