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Issue 26, 2011
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O–O Bond activation in H2O2 and (CH3)3C-OOH mediated by [Ni(cyclam)(CH3CN)2](ClO4)2: Different mechanisms to form the same Ni(iii) product?

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Abstract

Reaction of [NiII(cyclam)(CH3CN)2](ClO4)2 (1) with tert-butylhydroperoxide (TBHP) or H2O2, in acidic media results in a formation of [NiIII(cyclam)(CH3CN)2]3+ species (2), the nature of which is characterized by UV-vis, EPR and XPS. The formation rate of 2 is much higher when H2O2 is used as oxidant. In absence of acid, TBHP reacts with 1 generating the same Ni(III) species but, in contrast, no reaction is observed between H2O2 and 1. Addition of cis-stilbene as an oxidable substrate quenches the formation of Ni(III) for reaction with H2O2 only. Overall, these observations reveal a different reaction mechanism when reacting H2O2 with 1 than when reacting the same metal complex with TBHP, despite the fact that the final product is the same. The proposed pathways arising from these observations consist in a homolytic O–O cleavage for the reaction of 1 with TBHP in CH3CN, but a proton assisted heterolysis for the O–O activation in H2O2. Density functional calculations (B3LYP and OPBE) on the thermodynamic feasibility of the two reaction processes support the proposed mechanisms, since the O–O homolysis is strongly disfavored when H2O2 is used as reactant.

Graphical abstract: O–O Bond activation in H2O2 and (CH3)3C-OOH mediated by [Ni(cyclam)(CH3CN)2](ClO4)2: Different mechanisms to form the same Ni(iii) product?

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Supplementary files

Article information


Submitted
18 Nov 2010
Accepted
01 Apr 2011
First published
01 Jun 2011

Dalton Trans., 2011,40, 6868-6876
Article type
Paper

O–O Bond activation in H2O2 and (CH3)3C-OOH mediated by [Ni(cyclam)(CH3CN)2](ClO4)2: Different mechanisms to form the same Ni(III) product?

X. Solans-Monfort, J. L. G. Fierro, L. Hermosilla, C. Sieiro, M. Sodupe and R. Mas-Ballesté, Dalton Trans., 2011, 40, 6868
DOI: 10.1039/C0DT01605E

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