A side-on Mn(iii)–peroxo supported by a non-heme pentadentate N₃Py₂ligand: synthesis, characterization and reactivity studies

Abstract

A new non-heme Mn(iii)–peroxo (1a) has been generated, characterized and reactivity is in aldehyde deformylation reaction. A nucleophilic reactivity of 1a in aldehyde oxidation is proposed.

DFT Mechanistic Insights into Aldehyde Deformylations with Biomimetic Metal–Dioxygen Complexes: Distinct Mechanisms and Reaction Rules

“…The ONA mechanism was often applied to account for the deformylations with TM–O 2 complexes as deformylating reagents. ,,− We first investigated whether 3 [CuO 2 ] – could act similarly. At a glance, because of the anionic nature of 3 [CuO 2 ] – , the ONA mechanism appears reasonable.…”

“…TM–O 2 complexes often feature amphoteric reactivity, including the electrophilic reactivity as exhibited in the hydrogen atom abstraction reactions − and the nucleophilic reactivity as found in the aldehyde deformylations. ,,− In the past two decades, using aldehydes such as 2-phenylpropionaldehyde (2-PPA), trimethylacetaldehyde (TMA), cyclohexanecarboxaldehyde (CCA), and other electrophiles as probes, the nucleophilic reactivity of a wide range of TM–O 2 complexes has been investigated, where TM = V, , Mn, ,,,, Fe, , Co, , Ni, , and Cu . Notably, using O 2 as an oxidant, catalytic deformylation of 2-PPA has also been reported. ,, As de Visser and co-workers in 2021 have presented an excellent and comprehensive review on this topic, we herein highlight the works relevant to the present study.…”

“…Mechanistically, a widely accepted mechanism to account for aldehyde deformylations with TM–O 2 complexes is the outer-sphere nucleophilic attack mechanism, ,,− termed as ONA mechanism hereafter. Under the mechanism, the O 2 ligand undergoes nucleophilic attack at the aldehyde carbonyl carbon to start a deformylation reaction. ,,− Using a quantum mechanics/molecular mechanics (QM/MM) modeling method, Hackett and co-workers demonstrated the ONA mechanism to be feasible for the deformylation catalyzed by sterol-14α-demethylase (CYP51) .…”

“…Mechanistically, a widely accepted mechanism to account for aldehyde deformylations with TM–O 2 complexes is the outer-sphere nucleophilic attack mechanism, ,,− termed as ONA mechanism hereafter. Under the mechanism, the O 2 ligand undergoes nucleophilic attack at the aldehyde carbonyl carbon to start a deformylation reaction. ,,− Using a quantum mechanics/molecular mechanics (QM/MM) modeling method, Hackett and co-workers demonstrated the ONA mechanism to be feasible for the deformylation catalyzed by sterol-14α-demethylase (CYP51) . In the experimental studies, the ONA mechanism was often postulated. ,,− As exemplified in Scheme A, under the ONA mechanism, the reaction begins with nucleophilic attack to form an intermediate, followed by Baeyer–Villiger oxidation or hydrogen atom abstraction pathways, leading to the deformylation products.…”

“…Under the mechanism, the O 2 ligand undergoes nucleophilic attack at the aldehyde carbonyl carbon to start a deformylation reaction. ,,− Using a quantum mechanics/molecular mechanics (QM/MM) modeling method, Hackett and co-workers demonstrated the ONA mechanism to be feasible for the deformylation catalyzed by sterol-14α-demethylase (CYP51) . In the experimental studies, the ONA mechanism was often postulated. ,,− As exemplified in Scheme A, under the ONA mechanism, the reaction begins with nucleophilic attack to form an intermediate, followed by Baeyer–Villiger oxidation or hydrogen atom abstraction pathways, leading to the deformylation products. Because the mechanism involves abstraction of α-hydrogen of aldehydes (2-PPA and CCA) and TMA does not have an α-hydrogen, the deformylation of TMA (eq 2) terminates after the decomposition of the nucleophilic attack intermediate.…”