Gas phase infrared spectra of small polyatomic ions as a benchmark for theory

► Anions derived from trimethylboron have weaker B-C bonds than does trimethylboron. ► The theory of atoms in molecules (AIM) provides a consistent picture of bonding at trigonal centers. ► Carbocatiions and alkylboranes both have bond orders close to 1.5, based on AIM calculations. ► In contrast to silicon analogs, neutral alkylboranes are stabilized by hyperconjugation.