Mechanistic investigations of high-valent metal intermediates of biomimetic non-heme model systems
Metalloenzymes are known to play pivotal role in catalysing a plethora of biological and biochemical reactions. These transformations are directed by a variety of high-valent reactive intermediates that undergo crucial redox reactions by atom-transfer or electron-transfer or radical reaction pathways. These high-valent reactive intermediates of non-heme model systems are known to be influenced by factors like coordination motifs and topology, ligand architecture, pH, spin states of metal ions, solvation and temperature.1 The factors that govern the reactivity profiles are often associated with the mechanistic pathways followed. Hence, it is important to dig deep into the mechanistic details of the reactions performed by these model systems.
Non-heme iron-oxo intermediates have been identified as potential reactive intermediates in a variety of electrophilic reactions. It can catalyse C-H activation reactions and can also undergo heteroatom oxidation. Subtle modifications in a ligand skeleton can be seen to hugely accelerate reaction rates catalysed by non-heme iron-oxo complexes.2 Also, with the help of a series of structurally tweaked ligand frameworks, the governing factors that orchestrate the eccentric reactivity trends of iron-oxo moieties have been brought to the forefront.3 With the help of a couple of isomeric bispidine Mn(III)-peroxo complexes, a new mechanism for aldehyde deformylation reaction has been established. Keto-enol tautomerism in the reaction mechanism can be seen to trigger an electrophilic pathway instead of the commonly portrayed nucleophilic mechanism.4 Another intended engineering in the bispidine framework resulted in stabilizing a metastable non-heme iron(III)-alkylperoxo complex. These complexes are generally non-reactive. Surprisingly, however, versatile reactivity towards both electrophiles and nucleophiles have been observed for the same.
1. Mukherjee, G.; Sastri, C. V. Isr. J. Chem. 2020, 60, 1032-1048.
2. Mukherjee, G.; Lee, C. W. Z.; Nag, S. S.; Alili, A.; Cantú Reinhard, F. G.; Kumar, D.; Sastri, C. V.; de Visser, S. P. Dalton. Trans. 2018, 47, 14945-14957.
3. Mukherjee, G.; Alili, A.; Barman, P.; Kumar, D.; Sastri, C. V.; de Visser, S. P., Chem. Eur. J. 2019, 25, 5086-5098.
4. Cantu Reinhard, F. G.; Barman, P.; Mukherjee, G.; Kumar, J.; Kumar D.; Kumar D.; Sastri, C. V.; de Visser, S. P. J. Am. Chem. Soc. 2017, 139, 18328-18338.