Monoborane 2 , BH2, Its Ions and Derivatives

The species BHg was the subject of several investigations for the purpose of testing theoretical methods. Thus, the use of Walsh diagrams to predict bond angles for species such as BHg, [BHg] , and [BH2] by using just the ground-state wave function is successful for excited and ionized states [1]. 

Calculations on one-electron-bonded radical cations necessitated data for the radicals from which they derive, and thus ab initio molecular orbital calculations give values for the ionization energy for BH2 of 175 kcal/mol (6.72 eV) and 179.3 kcal/mol (7.78 eV), when HF/6-31G and MP2/6-31G methods are used, respectively [2]. BH2 as one of three test molecules was used to calculate partition functions from ab initio methods involving sums of states of molecules in their spatially degenerate lowest electronic states [3]. 

A calculation of the potential energy surface for the dissociation of the [BHJ radical using ab initio MO theory also provided information about the [BH2] radical. The reaction between BH2 and H2 is exothermic and affords BH3 and H via a nonconcerted pathway involving the intermediacy of the C2V or structures of BH4 [7]. 

The reaction of BH2 with NO was studied theoretically. The study used the optimized geometry for BH2 with r(BH)=1.186 A and (HBH)=126.6 . The most likely products are NH2 + BO and HBO + NH. The reaction rate is expected to be close to that for the dipole-dipole capture rate, to be independent of pressure, and to show only weak temperature dependence. Several possible intermediate isomers of BH2NO are considered and their geometries calculated [10]. 

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