Heavy Metals Make a Chain: A Catenated Bismuth Compound

Catenation is common for the light main-group elements whereas it is rare for the heavy elements. Herein, we report the first example of a neutral molecule containing a Bi₄ chain. It is prepared in a one-step reaction between bismuth trichloride and bis(diisopropylphosphino)amine in methanol suspension. The same reaction carried out in dichloromethane gives quite different products. All products have been characterized spectroscopically and using single-crystal X-ray analysis.

An Air-Stable, Neutral Phenothiazinyl Radical with Substantial Radical Stabilization Energy

The vital effect of radical states on the pharmacological activity of phenothiazine-based drugs has long been speculated. Whereas cationic radicals of N-substituted phenothiazines show high stability, the respective neutral radicals of N-unsubstituted phenothiazines have never been isolated. Herein, the 1,9-diamino-3,7-di-tert-butyl-N1 ,N9 -bis(2,6-diisopropylphenyl)-10H-phenothiazin-10-yl radical (SQH2 . ) is described as the first air-stable, neutral phenothiazinyl free radical. The crystalline dark-blue species is characterized by means of EPR and UV/Vis/near-IR spectroscopy, as well as cyclic voltammetry, spectro-electrochemical analysis, single-crystal XRD, and computational studies. The SQH2 . radical stands out from other aminyl radicals by an impressive radical stabilization energy and its parent amine has one of the weakest N-H bond dissociation energies ever determined. In addition to serving as open-shell reference in medicinal chemistry, its tridentate binding pocket or hydrogen-bond-donor ability might enable manifold uses as a redox-active ligand or proton-coupled electron-transfer reagent.

Hydrostibination

A rigid naphthalenediamine framework has been used to prepare antimony hydrides that feature LUMO shapes and energies similar to those found in secondary boranes. By exploiting this feature, we introduce the first examples of uncatalyzed hydrostibination reactions of robust C≡C, C=C, C=O, and N=N bonds as new elementary hydrometalation reactions analogous to hydroboration. These results endorse the notion of a diagonal relationship between the lightest p-block element and the heaviest Group 15 elements and may lead to the conception of novel reaction chemistry.