LAUSR

Abstract The heavier group 14 compounds, H2CYX2 and HXCYX2 (X = F, Cl, Br and I, Y = Si and Ge), were investigated by ab initio method. Equilibrium geometries, energies and bonding properties of H2CYX2/HXCYX2 were analyzed. Bader’s atoms-in-molecule (AIM), Pipek-Mezey localized molecular orbital and fuzzy bond orders (FBO) analyses were performed to investigate the bonding interactions in H2CYX2/HXCYX2. The C Y bond in H2CYX2/HXCSiX2 shows double bond feature, which is the main reason for that all H2CYX2/HXCYX2 are planar structures or close to planar structures. Y X and C X bonds have partial double bond feature as well due to the p-π conjugation effect between X atom and C Y π bond. The thermodynamic stability of H2CSiX2 decreases gradually as X goes from F to I, while that of HXCGeX2 has an opposite tendency. The trend of the thermodynamic stability in H2CGeX2 and HXCSiX2 is not pronounced. For H2CYX2 and HXCSiX2, the C Y bond is weakened gradually as X goes from F to I, and the C Si bond in H2CSiX2 (or HXCSiX2) is stronger than the C Ge bond in its Ge counterpart. In addition, the C Y bond in most of HXCYX2 is weaker than that of H2CYX2.