Journal
INORGANIC CHEMISTRY
Volume 50, Issue 22, Pages 11612-11622Publisher
AMER CHEMICAL SOC
DOI: 10.1021/ic201545a
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Funding
- OU [19205019]
- Ministry of Education, Culture, Sports, Science and Technology, Japan
- NRF/MEST of Korea through CRI
- GRL [2010-00353]
- WCU [R31-2008-000-10010-0]
- 2011 KRICT OASIS project
- Grants-in-Aid for Scientific Research [20108010, 20108001] Funding Source: KAKEN
- National Research Foundation of Korea [R31-2011-000-10010-0, 2010-00353] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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Oxidative dimerization of N,N-dimethylaniline (DMA) occurs with a nonheme iron(IV)-oxo complex, [Fe-IV(O)(N4Py)](2+) (N4Py=N,N-bis(2-pyridylmethyl)-N-bis-(2-pyridyl)methylamine), to yield the corresponding dimer, tetramethylbenzidine (TMB), in acetonitrile. The rate of the oxidative dimerization of DMA by [Fe-IV(O)(N4Py)](2+) is markedly enhanced by the presence of scandium triflate, Sc(OTf)(3) (OTf = CF3SO3-), when TMB is further oxidized to the radical cation (TMB center dot+). In contrast, we have observed the oxidative N-demethylation with para-substituted DMA substrates, since the position of the C-C bond formation to yield the dimer is blocked. The rate of the oxidative N-demethylation of para-substituted DMA by [Fe-IV(O)(N4Py)](2+) is also markedly enhanced by the presence of Sc(OTf)(3). In the case of para-substituted DMA derivatives with electron-donating substituents, radical cations of DMA derivatives are initially formed by Sc3+ ion-coupled electron transfer from DMA derivatives to [Fe-IV(O)(N4Py)](2+), giving demethylated products. Binding of Sc3+ to [Fe-IV(O)(N4Py)](2+) enhances the Sc3+ ion-coupled electron transfer from DMA derivatives to [Fe-IV(O)(N4Py)](2+), whereas binding of Sc3+ to DMA derivatives retards the electron-transfer reaction. The complicated kinetics of the Sc3+ ion-coupled electron transfer from DMA derivatives to [Fe-IV(O)(N4Py)](2+) are analyzed by competition between binding of Sc3+ to DMA derivatives and to [Fe-IV(O)(N4Py)](2+). The binding constants of Sc3+ to DMA derivatives increase with the increase of the electron-donating ability of the para-substituent. The rate constants of Sc3+ ion-coupled electron transfer from DMA derivatives to [Fe-IV(O)(N4Py)](2+), which are estimated from the binding constants of Sc3+ to DMA derivatives, agree well with those predicted from the driving force dependence of the rate constants of Sc3+ ion-coupled electron transfer from one-electron reductants to [Fe-IV(O)(N4Py)](2+). Thus, oxidative dimerization of DMA and N-demethylation of para-substituted DMA derivatives proceed via Sc3+ ion-coupled electron transfer from DMA derivatives to [Fe-IV(O)(N4Py)](2+).
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