Insight into the substitution reactions of silylenoid H 2 SiLiF with GeH 3 X (X = F, Cl, Br): a theoretical study

The unique substitution reactions of the three-membered-ring silylenoid H 2 SiLiF with GeH 3 X (X = F, Cl, Br) were investigated using ab initio and density functional theory calculations. All stationary points on the potential energy surfaces were optimized at the B3LYP/6-311 + G (d, p) level of theory and the QCISD method was then used to calculate the single-point energies. Theoretical calculations predicted that the substitution reactions of H 2 SiLiF with GeH 3 X proceed via two reaction paths (I and II), while forming the same product H 2 FSi–GeH 3 . In either pathway, there is one precursor complex (Q), one transition state (TS), and one intermediate (IM) connecting the reactants and products. The substitution reaction barriers of H 2 SiLiF with GeH 3 X for path I (48.49, 42.71, and 38.71 kJ mol −1 ) decreased with the increase for the same-family element X from up to down in the periodic table, whereas the substitution barriers for path II (6.51, 22.04, and 23.62 kJ mol −1 ) increased with the increase in atomic number of X (X = F, Cl, Br). Path II was more favorable than path I. All the substitution reactions of H 2 SiLiF with GeH 3 X were exothermic. The elucidation of the unique mechanism of these substitution reactions suggests a new reaction mode of silicon–germanium bond formation.