Enhancing Chemo- and Stereoselectivity in C–H Bond Oxygenation with H2O2 by Nonheme High-Spin Iron Catalysts: The Role of Lewis Acid and Multimetal Centers

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Abstract
Spin states of iron often direct the selectivity in oxidation catalysis by iron complexes using hydrogen peroxide (H2O2) on an oxidant. While low-spin iron(III) hydroperoxides display stereoselective C–H bond hydroxylation, the reactions are nonstereoselective with high-spin iron(II) catalysts. The catalytic studies with a series of high-spin iron(II) complexes of N4 ligands with H2O2 and Sc3+ reported here reveal that the Lewis acid promotes catalytic C–H bond hydroxylation with high chemo- and stereoselectivity. This reactivity pattern is observed with iron(II) complexes containing two cis-labile sites. The enhanced selectivity for C–H bond hydroxylation catalyzed by the high-spin iron(II) complexes in the presence of Sc3+ parallels that of the low-spin iron catalysts. Furthermore, the introduction of multimetal centers enhances the activity and selectivity of the iron catalyst. The study provides insights into the development of peroxide-dependent bioinspired catalysts for the selective oxygenation of C–H bonds without the restriction of using iron complexes of strong-field ligands.
Funding Information
  • Council?of?Scientific and Industrial Research, India
  • Anusandhan National Research Foundation (CRG/2019/006393)

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