Theoretical investigation of the XHgXeX and HHgXeX (X = F, Cl, Br) compounds

The bond lengths, characteristic vibrational frequencies, atomic charge distributions, bonding character, and relative energies of the linear noble gas compounds XHgXeX and HHgXeX (X = F, Cl, Br) were investigated at both the MP2 and CCSD(T) levels of theory. According to the CCSD(T) calculations, (i) FHgXeF, HHgXeF, HHgXeCl, HHgXeBr, and ClHgXeCl are higher in energy by 63.61, 70.87, 73.57, 71.91, and 70.37 kcal/mol, respectively, than the corresponding global minimum complexes X(H)HgX⋯Xe; (ii) these five compounds are lower in energy by 25.35, 29.45, 12.49, 7.78, and 6.96 kcal/mol, respectively, than the corresponding three-body dissociation limits X(H)Hg + Xe + X; (iii) the reaction barrier energies for these five compounds to dissociate into the corresponding global minimum complexes X(H)HgX⋯Xe through the bending transition structures are 26.92, 15.74, 10.90, 10.45, and 20.27 kcal/mol, respectively. Thus these five compounds are metastable and may be prepared and identified in the low-temperature xenon matrix.