Alkane oxidation by the system ‘tert‐butyl hydroperoxide–[Mn₂L₂O₃][PF₆]₂ (L = 1,4,7‐trimethyl‐1,4,7‐triazacyclononane)–carboxylic acid’

Abstract

The kinetics of cyclohexane (CyH) oxygenation with tert‐butyl hydroperoxide (TBHP) in acetonitrile at 50 °C catalysed by a dinuclear manganese(IV) complex 1 containing 1,4,7‐trimethyl‐1,4,7‐triazacyclononane and co‐catalysed by oxalic acid have been studied. It has been shown that an active form of the catalyst (mixed‐valent dimeric species ‘MnIIIMnIV’) is generated only in the interaction between complex 1 and TBHP and oxalic acid in the presence of water. The formation of this active form is assumed to be due to the hydrolysis of the MnOMn bonds in starting compound 1 and reduction of one MnIV to MnIII. A species which induces the CyH oxidation is radical tert‐BuO. generated by the decomposition of a monoperoxo derivative of the active form. The constants of the equilibrium formation and the decomposition of the intermediate adduct between TBHP and 1 have been measured: K = 7.4 mol−1 dm3 and k = 8.4 × 10−2 s−1, respectively, at [H2O] = 1.5 mol dm−3 and [oxalic acid] = 10−2 mol dm−3. The constant ratio for reactions of the monomolecular decomposition of tert‐butoxy radical (tert‐BuO. → CH3COCH3 + CH) and its interaction with the CyH (tert‐BuO. + CyH → tert‐BuOH + Cy.) was calculated: 0.26 mol dm−3. One of the reasons why oxalic acid accelerates the oxidation is due to the formation of an adduct between oxalic acid and 1 (K ≈ 103 mol−1 dm3). Copyright © 2007 John Wiley & Sons, Ltd.

Oxidation of Organic Compounds with Peroxides Catalyzed by Polynuclear Metal Compounds

“…This system works efficiently only in the presence of an added organic acid. This acid was acetic acid, and later it was found that oxalic acid is even more effective [112][113][114][115][116][117]. Thus, for example, the system complex 24/oxalic acid/H2O2/O2 gives products in oxidation cyclohexane with yield up to 50% (TON = 2700) [115].…”

“…Thus, for example, the system complex 24/oxalic acid/H 2 O 2 /O 2 gives products in oxidation cyclohexane with yield up to 50% (TON = 2700) [115]. Other organic acids also accelerate the oxidation reaction [102][103][104][105][106][107][108][109][110][111][112][113][114][115][116][117][118][119][120].…”

Manganese‐Catalyzed Oxidation with Hydrogen Peroxide

“…CÀH activation with manganese-based catalysts is an area of continuing interest, with considerable attention being given to systems employing peracetic acid [135] and iodosylarenes [136]. Nevertheless, several groups have demonstrated that H 2 O 2 can also be employed to effect alkane oxidation with the help of Mn catalysts [137] and Fe catalysts [138].…”

Oxidation of Reactive Alcohols with Hydrogen Peroxide Catalyzed by Manganese Complexes

“…A relevant soluble polymer-bound Mn(IV) complex with N-alkylated 1,4,7-triazacyclononane was used as a catalyst in the H 2 O 2 oxygenation of alkanes [82]. We have also demonstrated that alkanes and olefins can be oxidized by tert-butyl hydroperoxide [72,95,96] or peroxyacetic acid [81,97] using complex 1a as a catalyst. The reaction with tert-butyl hydroperoxide is significantly accelerated in the presence of a small amount of a carboxylic acid [72,96].…”

“…We have also demonstrated that alkanes and olefins can be oxidized by tert-butyl hydroperoxide [72,95,96] or peroxyacetic acid [81,97] using complex 1a as a catalyst. The reaction with tert-butyl hydroperoxide is significantly accelerated in the presence of a small amount of a carboxylic acid [72,96]. Veghini, Fischer and coworkers [98] prepared insoluble salt of formula [LMn(l-O) 3 MnL] 2 [SiW 12 O 40 ] (catalyst 1b) which turned out to be an active catalyst in the oxidation of alcohols [77,98] and olefins [98].…”