R_2C=GeH_2和R_2Ge=CH_2结构与成键特征的理论研究

Theoretical Study on the Structure and Bonding Character of the R_2Ge=CH_2 and R_2C=GeH_2

用密度泛函理论(DFT),在B3LYP/6-31+G(d,p)水平上研究了取代基对二取代锗烯R2Ge=CH2和R2C=GeH2[R=H,OH,NH2,SH,PH2,F,Cl,Br,(NHCH)2,CH3,(CH)2]的影响.研究发现π供电子取代基在碳上时更能引起分子结构在锗端的锥型化.碳原子上的π电子给予取代基的给电子效应越强,R2C的单-三态能量差越大,π电子的反极化效应就越强,使得化合物的结构在锗端发生的弯曲越明显,从而使得弯曲结构更稳定.和前人的计算相比,碳上的给电子取代基对GeH2结构影响大于它对SiH2的影响.

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 AEsT 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 = Sill2 system, the π-electron-donating substituents at the carbon atom have more effective influence on inducing GeH2 a bent structure than that of Sill2.