Biradical formation vs. π‐bonding: The low‐valent, highly reactive pnictogen compounds PnCH3 (Pn=As, Sb) have been generated in situ by controlled homolysis of Pn(CH3)3 in the gas phase and investigated by photoelectron–photoion coincidence spectroscopy. This allowed us to establish trends in nature's strategy to stabilize low‐valent pnictogen species either by tautomerization with concomitant multiple bond formation (HPn=CH2) or by biradical formation (Pn−CH3). The graphic illustrates the energetic steps separating the isomers of these fundamentally important group 15 compounds. More information can be found in the Research Article by C. Lichtenberg, P. Hemberger, I. Fischer and co‐workers (DOI: 10.1002/chem.202300637).

Methyl and methylene compounds of arsenic and antimony have been studied by photoelectron photoion coincidence spectroscopy to investigate their relative stability. While for As both HAs=CH2, As−CH3 and the methylene compound As=CH2 are identified in the spectrum, the only Sb compound observed is Sb−CH3. Thus, there is a step in the main group 15 between As and Sb, regarding the relative stability of the methyl compounds. Ionisation energies, vibrational frequencies and spin‐orbit splittings were determined for the methyl compound from photoion mass‐selected photoelectron spectra. Although the spectroscopic results for organoantimony resemble those for the previously investigated bismuth compounds, EPR spectroscopic experiments indicate a far lower tendency for methyl transfer for Sb(CH3)3 compared to Bi(CH3)3. This study concludes investigations on low‐valent organopnictogen compounds.