Dioxygen Activation by Internally Aromatic Metallacycle: Crystallographic Structure and Mechanistic Investigations

Abstract

Summary Mononuclear metal-peroxo species are invoked as the key intermediates in metalloenzymatic or synthetic catalysis. However, either transience or sluggishness reactivity of synthetic analogs of metal-peroxo species impedes our understanding of oxygen activation mechanism. Herein, we designed and characterized a dioxygen-derived mononuclear osmium-peroxo complex, in which the peroxo ligand is stabilized by internally aromatic metallacycle. We demonstrate that the osmium-peroxo species shows catalytic activity toward promoterless alcohol dehydrogenations. Furthermore, computational studies provide a new mechanism for the osmium-peroxo-mediated alcohol oxidation, starting with the concerted double-hydrogen transfer and followed by the generation of osmium-oxo species. Interestingly, the internally aromatic metallacycle also plays a vital role in catalysis, which mediates the hydrogen transfer from osmium center to the distal oxygen atom of Os–OOH moiety, thus facilitating the Os–OOH→Os=O conversion. We expect that these insights will advance the development of aromatic metallacycle toward aerobic oxidation catalysis.

An osmium-peroxo complex for photoactive therapy of hypoxic tumors

“…The synthesis of the osmium-peroxo complex Os2 was based on our previously reported method 36 , and the characterization data can be found in the Supporting Information (SI, experimental section and Supplementary Figs. 1–3 ).…”

Recent Advances in the Reactions of Cyclic Carbynes

“…Novel metallacycles derived from the reactivity studies of metallapentalynes exhibited great application prospects in various areas, such as near-infrared dyes [47], photothermal therapy [74][75][76][77], phototherapy [78], and self-healing materials [79], enabling their potential applications in materials science and biomedicine. Future developments of metallabenzynes and metallapentalynes and exploration of their potential applications in catalysis [60], materials science and biomedicine would not only extend our perception of aromaticity in metallacycles, but also further enrich fundamental organometallic chemistry.…”

“…Meanwhile, the labile aldehyde was oxidized to carboxylic acid, affording unprecedented OCCCO-type pentadentate chelates 69. The second example was the direct oxygenation of the metal center in the carbolong complex 70 [60]. The mixture of osmapentalyne 70 and excess sodium methoxide under oxygen atmosphere resulted in almost quantitative formation of osmapentalene 71, in which the dioxygen was bound to the metal center.…”

An osmium-peroxo complex for photoactive therapy of hypoxic tumors

“…The synthesis of the osmium-peroxo complex Os2 was based on our previously reported method, [16] and the characterization data can be found in Figures S1-S3 in the Supporting Information (SI). Os2 is highly stable in phosphate-buffered saline (PBS) at pH = 7.4 or in Dulbecco's Modi ed Eagle Medium (DMEM) cell culture media in the dark at room temperature (rt) (Figures S4 and S5), and is also stable in the presence of reducing agents such as NADH, GSH, or Cys (Figure S5).…”

“…We have investigated an osmium-peroxo complex (Os2), whose structure signi cantly improves the thermal stability of the osmium-peroxo moiety. [15,16] Upon photoactivation with 465 nm light, Os2…”