Ions and Other Derivates of BH

Photoionization mass spectrometric studies of BHg, produced by the pyrolysis of BgHg, allowed the appearance potential of [BH]+, from the process BH3 + hv [BH] + H2 + e , to be measured as 308.38 0.39 kcal/mol. This value is deemed by the authors to be close to the true value [7]. Energetics of the B + H2- -[BH] + H reaction channel were studied at the ab initio level. Of the allowed processes, only the B- ( P) atoms are considered to be reactive species. The internuclear distances for [BH] (2I+), [BH] (211), and H2 ( Ig), 1.22, 1.26, and 0.7415 A, respectively, are in good agreement with experiment. The triplet potential energy surface is obtained and it is deemed useful for interpretation of results from crossed beam experiments [11]. 

The potential energy surface of CBH3, as calculated by ab initio methods, reveals that the singlet methylborylene, [CHaB], is a minimum. Although CH2=BH is more stable by 24.3 kcal/mol, the 1,2-H shift barrier is 25.0 kcal/mol. The entire triplet state surface lies 43.6 kcal/mol above the singlet state which is stabilized by n donation from the methyl group [8]. Structural parameters are given in Fig. 2-1. Calculated vibrational frequencies for the species are 2877(e), 2818(ai), 1390(e), 1297(ai), 865(ai), and 590(e) cm- [7]. 

The electron affinity for BH was estimated using methods similar to those in [5]. The value is given as 0.13 eV and cannot be compared with experimental data (which are not available). Data calculated for [BH]- in this study include r=1.245 A, v([BH] ) = 2275 cm and the proton affinity is 390.9 kcal/mol [8]. 

In studying chemical reactions between NO and BH (generated by excimer laser photolysis of B2H6) [9], the results are consistent with the formation of an excited intermediate HBON. This results from a theoretical treatment of the BH + NO reaction with respect to the most likely dissociation products BO and NH [10]. 

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