Terminal Copper Nitrenoid Formation and Reactivity Induced by Absorption to an Antenna Ligand.

Copper nitrenoids are key intermediates in copper-catalyzed direct C-H amination reactions. Further development of this important reaction relies on knowing the properties and reactivity of the nitrenoid intermediates. This work utilizes antenna ligands to form copper nitrenoid complexes and monitor the consecutive C-H amination reactions under well-defined single-molecule conditions in the gas phase. The [Cu(Lphoto)(Lazide)]+ precursors (Lphoto is a bidentate antenna ligand, and Lazide is an organic azide) were stored in an ion trap at 3.5 K and irradiated by visible light, which resulted in denitrogenation of the complex. Further irradiation of the copper nitrenoid led to the consecutive C-H amination of the antenna ligand. The nitrenoid complexes, as well as the products of the C-H amination, were characterized by helium tagging IRPD spectroscopy, and the mechanism was described by DFT calculations. This research demonstrates that the antenna ligands can be used to promote the denitrogenation of metal azides in the gas phase and also channel the internal energy to promote further reactivity, which opens a new way to study the reactivity of highly reactive species under well-defined conditions.

Copper arylnitrene intermediates: formation, structure and reactivity.

The mechanism of oxidation of arylamines by copper enzymes is not clarified yet. Here, we explored a reaction between a possible high-valent copper(ii)-oxyl intermediate and arylamine. We have employed a TPA ligand (TPA = tris(2-pyridylmethyl)amine) with the NH2 group in position 2 of one of the pyridine rings (TPANH2). This model system allows generation of [(TPANH2)Cu(O)]+ in the gas phase, which immediately undergoes a reaction between the arylamino group and the copper oxyl moiety. The reaction leads to elimination of H2O and formation of a copper-nitrene complex. The structure of the resulting copper-nitrene complex was confirmed by infrared spectroscopy in the gas phase. We show that the copper-nitrene complex reacts by hydrogen atom transfer with 1,4-cyclohexadiene and by an order of magnitude faster by a double hydrogen atom transfer with ethanethiol and methanol. DFT calculations explain the formation of the copper nitrene as well as its reactivity in agreement with the experimental findings.

Correction: Synthesis of polyoxometalate clusters using carbohydrates as reducing agents leads to isomer-selection.

Correction for 'Synthesis of polyoxometalate clusters using carbohydrates as reducing agents leads to isomer-selection' by Eric Janusson et al., Chem. Commun., 2019, DOI: 10.1039/c9cc02361e.

Synthesis of polyoxometalate clusters using carbohydrates as reducing agents leads to isomer-selection.

By using sugars as the reducing agents, we demonstrate that it is possible to control the self-assembly of polyoxomolybdates through selective preparation of a single heteropolyanion isomer. d-(-)-Fructose has been proved to be an effective reducing sugar compared to the chemically similar carbohydrate d-(+)-glucose. The gentle reduction results in favourable formation of the Wells-Dawson type gamma isomer in 6-fold reduced form at room temperature.