A new type of nickel and palladium complexes with non-innocent b-diketiminate ligand having redox active phenol groups, 2,4-di-tert-butyl-6-(((1E,2E)-3-((3,5-di-tert-butyl-2-hydroxyphenyl) amino)-2-nitroallylidene)amino)phenol (LH 3 , fully protonated form) have been developed, and the structure, physical properties, and reactivity of their one-electron and two-electron oxidized complexes, [M II (L ·2-)] and [M II (L -)] + (M = Ni II or Pd II ) have been examined in detail. The two-electron oxidized forms of both complexes, [M II (L -)] + , exhibited hydrogen atom abstraction ability from 1,4-cyclohexadiene (CHD) comparable to its copper analog [Cu II (L -)] + (Dalton Trans. 2013; 42: 2438-2444). The oneelectron oxidized form of palladium complex, [Pd II (L ·2-)], was also found to oxidize CHD, whereas the nickel analog, [Ni II (L ·2-)], exhibited photo-induced oxidation ability of CHD.
Hydroxylation of cyclohexane with m-chloroperbenzoic acid was examined in the presence of an iron(III) complex supported by a trianionic planar tetradentate ligand. The present reaction system shows a high turnover number of 2750 with a high product selectivity of alcohol (93%). The turnover frequency was 0.51 s −1 , and the second-order rate constant (k) for the C−H bond activation of cyclohexane was 1.08 M −1 s −1 , which is one of the highest values among the iron complexes in the oxidation of cyclohexane so far reported. The present catalytic system can be adapted to the hydroxylation of substrates having only primary C− H bonds such as 2,2,3,3-tetramethylbutane as well as gaseous alkanes such as butane, propane, and ethane. The involvement of an iron(III) acyl peroxido complex as the reactive species was suggested by spectroscopic measurements of the reaction solution.Article pubs.acs.org/IC
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