Is one electron sufficient to bring about significant σ bonding between two atoms? The chemist's view on the chemical bond is usually tied to the concept of shared electron pairs, and not too much experimental evidence exists to challenge this firm belief. Whilst species with the unusual one-electron σ-bonding motif between homonuclear atoms have so far been identified mainly by spectroscopic evidence, we present herein the first crystallographic characterization, augmented by a detailed quantum-chemical validation, for a radical anion featuring a B⋅B one-electron-two-center σ bond.

Temperature treatment (120 °C, C 6 H 6 or toluene, sealed glass ampule) of the C 1 -symmetric dimer of 9H-9-borafluorene (1) 2 leads to the ring-opened dimer 1,2:1,2bis(2,2′-biphenylylene)diborane(6) (2), 2,2′-bis(9-borafluoren-9-yl)biphenyl (3), and 1,2-(2,2′-biphenylylene)diborane(6) (4). 2 readily crystallizes from the thermolysis mixture in 34% yield. The ditopic borane 3 does not form in preparatively useful quantities but has been made accessible through salt metathesis between 9-bromo-9-borafluorene and donorfree 2,2′-dilithiobiphenyl in almost quantitative yields. Even at 330 K, the 1 H and 13 C{ 1 H} NMR spectra of 3 are broadened almost beyond interpretability. X-ray crystallography and molecular modeling studies on 3 indicate a highly restricted conformational space. 3 binds THF and SMe 2 only weakly but readily forms a stable B−N adduct upon addition of 2 equiv of pyridine (py). The resulting 3•py 2 (X-ray crystal structure) shows perfectly well resolved NMR spectra. Article pubs.acs.org/Organometallics

True one-electron collision systems provide an ideal testing ground for theory. Absolute cross sections for charge transfer in the collision systems Li2+ + He2+ and Li2+ + Li3+ have been measured for centre-of-mass energies between 52 and 148 keV and 6 and 63 keV, respectively. The data are compared with calculations using the two-centre basis generator method. A fair agreement between the experimental data and the calculations is found.

A general Pd-catalyzed, enantioselective three-component synthesis of α-arylglycines starting from sulfonamides, glyoxylic acid derivatives, and boronic acids was developed. This operationally straightforward procedure enables the preparation of a wide variety of α-arylglycines in high yields and excellent levels of enantioselectivity from a simple set of readily available starting materials. Incorporation of Pbf-amides gives a racemization-free access to N-unprotected α-arylglycines.

Using the crossed-beams technique, we have measured absolute total cross sections for electron capture from H2+ molecular ions by He2+ and Ar2+ at relative velocities vrel = 0.7-1.3 au. With He2+ a distinct maximum around vrel = 1 au is observed, which can be attributed to the large Q-value for the dominant channel of this reaction. Theoretical calculations using an atomic model for ion-molecule collisions are in very good agreement with the experimental data.