Theoretical investigation of the reducing capacity of sodium borohydride and sodium acetoxyborohydride derivatives

摘要

The reducing capacity of sodium borohydride and its acetoxy derivatives was studied. Density functional theory using four different functionals were used to investigate the enthalpies, charges and molecular structures of four distinct reactions associated with hydride release. The theoretical results in the gas phase reinforce the experimental observations that the acetoxyborohydride derivative reducing capacities are a consequence of both the inductive electron-withdrawing ability of the acetoxy group and the steric bulk surrounding the B-H bond. The electron acceptor effect of the acetoxy group provided a linear relation between the boron GAPT charges and the enthalpy necessary to remove the hydride from sodium borohydride, justifying the smaller or even nonexistent reductor capacity of more substituted borohydrides. (c) 2006 Elsevier BV.. All rights reserved.