Substituent effects on the disubstituted heavier analogues of R₂C＝GeH₂ and R₂Ge＝CH₂ [R＝H, OH, NH₂, SH, PH₂, F, Cl, Br, (NHCH)₂, CH₃, (CH)₂] were investigated using density functional theory [B3LYP/6-31＋G(d, p)]. The major conclusion was that the stronger the π-donation of the substituents, the larger the ΔE_ST of CR₂ and the stronger the π-electron reversed-polarization effect. As the π-electron reversed-polarization effect increased, the distortion of GeH₂ fragment increased, and the stability of the bent structure increased. In addition, the π-electron-donating substitution at the carbon atom was more effective at inducing a bent structure than at the Ge atom. In contrast to the R₂C＝SiH₂ system, the π-electron-donating substituents at the carbon atom have more effective influence on inducing GeH₂ a bent structure than that of SiH₂.

Key words: density functional theory (DFT), germene, reversed polarization effect