Use of ELF and AIM parameter ratios for bond order characterization of two-, three-, and four-coordinate gallium hydrides

Abstract

Calculations at the B3LYP/6-311+ G(d,p)//B3LYP/6-311 + G(d,p) level involving the electron localization function (ELF) and atoms-in-molecules (AIM) methods have been carried out for two-, three-, and four-coordinate gallium hydrides present in Na and Li salts and as the isolated di-anionic species, for some isoelectronic germanium compounds, and for several neutral gallium hydrides. Using the ratio of delocalization indices and bond basin populations referenced to reasonable standards, formal bond orders are derived. While chemically expected bond orders are found in most cases, the situation in the [HGaGaH]2- species appears to lie intermediate between bonds of order 2 and 3, and that for neutral trans-bent HGaGaH is found to be best described as a bond of order 1. In these cases the larger bond order predicted by ELF bond basin populations evidently results from overlap of the bond basin into the lone pair (nonbonding) region of the molecule.