BX_3与C=C之间p-π作用的量子化学研究

用量子化学计算方法对BX3(X=H,F,Cl)与C‖C之间通过p-π作用形成的复合物进行了研究.计算结果表明,各复合物中BX3均位于π键的上方,并且偏向于氢原子数较多的碳原子一侧.BH3与C‖C的作用是由π键中的电子通过向B的空p轨道转移而形成,但BF3和BCl3与C‖C的作用只是通过微弱的分子间作用力结合,复合物的形成使分子的振动光谱随作用的强弱而出现一定的红移现象.

A Quantum Chemistry Study on p-π Interaction between BX3(X=H, F, Cl) and C＝C Bond

Geometries and combination energies for the complexes between alkenes C_nH_(2n)(n=2,3,4) and BX_3(X=H,F,Cl) are predicated at B3LYP/6-311+G(2d,p) level. The results showed that the BX_3 locate exactly above the double bond of alkenes and close to the terminal carbon atoms to which there are more hydrogen atoms attached. The complexes of BH_3 are formed based on the fact that the π electron of the double bond transfers to the empty p orbital of boron atoms. But the formations of the complexes about BF_3 and BCl_3 only rely on the weak intermolecular forces. The calculated outcomes showed that when the complex formed their vibration spectrum moved to the red side and the frequency shifts are relative to the stabilities of the complexes.