Formation and identification of borane radical anions isolated in solid argon

The infrared (IR) spectrum of borane(3) anions (BH₃^-) isolated in solid Ar was recorded; two vibrational modes were observed at 2259.4 and 606.6 cm^-1, which were assigned to the BH₂ stretching (ν₃) and out-of-plane large-amplitude (ν₂) modes, respectively. These anions were produced by the electron bombardment of an Ar matrix sample containing a small proportion of B₂H₆ and H₂ during matrix deposition or by the photolysis of single-bridged-B₂H₅^- in an Ar matrix with the selected ultraviolet light. The band positions, relative intensity ratios, isotopic splitting pattern, and isotopic shift ratios of the observed IR features of BH₃^- are generally in good agreement with those predicted by the B2PLYP/aug-cc-pVTZ method.