The role of theory in studies of the diborane pyrolysis sequence

Abstract

- Theoretical studies to 4th order, or at coupled cluster levels using large basis sets have yieldeda transition state for the reaction of BH3 with B2H6. This state is about 20 kcal/mole less stable than B3H9(C3v,,) and some 8 or 12 kcal/mole higher than H2 plus B3H7 of symmetry C2v or CS) respectively. Therefore, most probably, B2H6 + BH3 yields B3H7 + H2 directly. Neither B3H9 (C3V,) nor bh5trap BH3 in usual pyrolysis conditions, and B2H8 to B2H4 and H2 has a higher barrier. A different BH3 adduct to B2He, forming a three-center bond between B of BH3 and H (terminal) of B2hq, has AEe (electronic) of -1.5 kcal/mole at the (531/31)MBPT(2)level. This intermediate, suggested by Fellner, needs further study. © 1991, IUPAC