Homolytic B–Cl bond dissociation energies of chloroborane-type molecules

Abstract

This study reports accurate gas-phase homolytic B–Cl bond dissociation energies, obtained using the benchmark-quality W1w thermochemical protocol, for a set of 25 chloroborane-type molecules (known herein as the BCl25BDE dataset). The BDEs of these species differ by as much as 136.5 kJ mol^-1 at 298 K, with (BH₂)₂BCl having the lowest BDE (388.5 kJ mol^-1 at 298 K) and (CH₃)HBCl having the highest (525.1 kJ mol^-1 ).  Using the W1w BDEs as reference values, the accuracy of a diverse set of more economical DFT procedures (which may be applied to the study of molecules sufficiently large that the use of benchmark-quality methods such as W1w is rendered computationally prohibitive) have been investigated. As a result of this analysis, the most accurate methods for the computation of B–Cl BDEs are ωB97/A'VQZ (MAD = 3.0 kJ mol^-1 ) and M06/A'VTZ (MAD = 3.2 kJ mol^-1 ). The double-hybrid functional DSD-PBEP86 in conjunction with the A'VQZ basis set (MAD = 4.0 kJ mol^-1 ) was found to give the lowest largest deviation (LD = 6.4 kJ mol-1 ) of any of methods considered in this assessment study.