摘要
为探讨金属铑的催化作用的本质,本文用赝势价轨道从头算方法研究了H_2,CO,N_2与Rh,Rh_2的相互作用。通过对H_2,CO,N_2与Rh,Rh_2几种接近方式的能量计算,发现当H_2与Rh_2以平行方式接近时,H_2发生解离,以其余方式接近时H_2与Rh,Rh_2没有明显的相互作用;CO在与Rh,Rh_2相互作用时都保持分子状态,但碳氧键有不同程度的减弱;当N_2以平行方式接近Rh_2时,氮分子键长被拉到相当于N—N单键的键长,N_2与Rh,Rh_2以顶位、桥位方式接近时,氮分子键仅有一定的减弱。本文还用前线轨道理论解释了计算结果。
Rhodium metal is a good catalyst for many organic reactions. In order to elucidate the nature of the activation of substrate by Rh, an ab initio method was used to study the interaction of H2, CO and N2 with Rh or Rh2.ECP(effective core potential) and DZ basis sets were used for Rh, while STO-3G was used for C, O, N, and 6-31G for H. Three kinds of approach (side-on,on-top,bridge) were chosen as models for the interaction. The calculated results showed that the side-on approach was the most effective model for H2-Rh2 system, dissociaton of H2 molecule occurred in side-on approach, while there was no inheraction in other approaches. CO interacted with Rh2 in bridge approach with the bond between carbon and oxygen weakened, the bond length of CO was lengthened from 0.1146 nm to 0.1232 nm. As for the interaction of N2 with Rh2, the bond length of N2 molecule was lengthened to about that of single bond in side-on approach, in other approaches, the results were similar to that of CO. All the results were explained with the frontier orbital theory.
基金
国家自然科学基金
