摘要
本文用CNDO方法研究了配合物(Cp_2Ti)_2AlH_4CH_3(Ⅰ),(Cp_2Ti)_2AlH_4Cl(Ⅱ)和(Cp_2Ti)_2AlH_4BH_4(Ⅲ)的电子结构和其催化活性的关系。结果表明,从Ⅰ到Ⅲ,随着Ⅹ吸电子能力增加,HOMO能量、在HOMO中氢桥骨架(Ti(μ-H)_2AlX(μ-H)_2Ti)成分、Al原子的电荷密度以及在LUMO中Ti原子成分均依次下降,但Ti—H键级依次上升,这些与在烯烃加氢和烯烃异构化反应中,Ⅰ的催化活性最强,Ⅱ其次,Ⅲ最弱这一实验结果相符。
A theoretical study on the relation between the electronic structure and catalytic activity of complexes (Cp2Ti)2AlH4CH3( Ⅰ ),(Cp2Ti)aAlH4-C(Ⅱ) and (Cp2Ti)2AlH4BH4(Ⅲ) has been performed by CNDO/2 method. The results indicated that the orbital energies of HOMO, the contribution of hydrogen bridge skeleton (Ti(μ-H)2AlX(μ-H)2Ti) to HOMO, the net charges on Al and the contribution of Ti atoms to LUMO decrease successively from ( Ⅰ ) to (Ⅲ), but Mulliken bond orders of Ti-H increase successively from (Ⅰ) to (Ⅲ). These are in agreement with the experiment results, i.e. ( Ⅰ) has the highest catalytic activity and ( Ⅲ ) has the lowest activity in the hydrogenation and isomerization reaction of olefins.
