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An efficient methyltrioxorhenium(VII)-catalyzed transformation of hydrotrioxides (ROOOH) into dihydrogen trioxide (HOOOH).

Dihydrogen trioxide (HOOOH) is formed nearly quantitatively in the low-temperature (-70 degrees C) methyltrioxorhenium(VII) (MTO)-catalyzed transformation of silyl hydrotrioxides (R3SiOOOH), and some acetal hydrotrioxides, in various solvents, as confirmed by 1H, and 17O NMR spectroscopy. The calculated energetics (B3LYP) for the catalytic cycle, using H3SiOOOH as a model system, is consistent with the experimentally observed activation energy (9.5 +/- 2.0 kcal/mol) and a small kinetic solvent isotope effect (kH2O/kD2O = 1.1 +/- 0.1), indicating an initial concerted reaction between the silyl hydrotrioxide and MTO in the rate-determining step. With the addition of water in the next step, the intermediate undergoes a sigma-bond metathesis reaction to break the Re-OOOH bond and form HOOOH, together with the second dihydroxy intermediate. The final step in the catalytic cycle involves a second, catalytic water that lowers the barrier to form H3SiOH and MTO.

The search for protonated dihydrogen trioxide (HOOOH): insights from theory and experiment.

Protonated dihydrogen trioxide (HOOOH) has been postulated in various forms for many years. Protonation can occur at either the terminal (HOOO(H)H(+)) or central (HOOH(OH)(+)) oxygen atom. However, to date there has been no definitive evidence provided for either of these species. In the current work we have employed ab initio methods, CCSD(T) and MP2, with a large basis set (6-311++G(3df,3pd)) to determine the relative stabilities of these species. It is shown that the terminally protonated species is strongly favored relative to the centrally protonated species (DeltaE = 15.8 kcal/mol, CCSD(T)//MP2). The mechanism of formation of HOOO(H)H(+) was determined to occur with a low barrier with the H(3)O(+) occurring in a thermoneutral reaction (DeltaE = -0.3 kcal/mol, CCSD(T)//MP2). Although HOOO(H)H(+) exists as a stable intermediate, it is extremely short-lived and rapidly decomposes (DeltaE* = 8.6 kcal/mol, MP2) to H(3)O(+) and O(2)((1)Delta(g)). The decomposition reaction is stabilized by solvent water molecules. The short-lived nature of the intermediate implies that the intermediate species can not be observed in (17)O NMR spectra, which has been demonstrated experimentally.