Can silacetylene be observed? A theoretical treatment of the tunneling effect

The potential energy surface for the 1,2-hydrogen shift converting silavetylene to silylidene, HSiCH→Si=CH2, has been calculated by means of ab initio molecular orbital methods up to the QCISD (T) level with 6-311++G(3df, 3pd) basis set. The geometries and energetics obtained were utilized to calculate the rate constants for the isomerization process including the tunneling correction over a wide range of temperatures. The tunneling probability has been treated using the WKB method with an analytical polynomial function of the energy potential. Our results suggest that the detection of silacetylene (HSiCH) might be possible with an instrument with nanosecond resolution. Detection of deuterium-substituted silacetylene could be easier. The half-life (t12) of HSiCH are about 10−8 and 5 × 10−6 s, respectively. The heats of formation at 0 K are predicted to be ΔHf0(H2C=Si)= 84.5±2 kcal/mol and ΔHf0 (HSiCH) = 118.3±2 kcal/mol.