Ab initio study of the formation of B3H7 derivative from B3H8 anion protonation

Formation of B3H7 species from the protonation of B3H8- has been studied by ab initio calculations at the HF and correlated MP2 levels using extended basis set 6-31 + G**. Two elementary processes, B3H8- + H+ --> B3H9 and B3H 9 --> B3H7 + H-2, have been investigated. The calculated absolute values of B3H8- + H+ --> B3H9 protonation energy are very high (above 314 kcal mol(- 1)). Loss of molecular hydrogen from B3H9 proceeds with an activation barri er above 12 kcal mol(-1), leading to a B3H7 one-bridged structure. The acti vation barrier of reverse reaction is found non-negligible when the zero-po int energy correction is added. The calculated energy and activation barrie rs of B3H7 rearrangement are small, confirming the fluxional behaviour for this species. However, a mechanism of B3H7 formation is proposed. The inclu sion of a solvent reaction field using water as a solvent (epsilon = 78.54) has a small influence on the energies and molecular properties. (C) 1999 E lsevier Science B.V. All rights reserved.