استخدام نظرية تابع الكثافة لدراسة آلية التبادل في بعض معقدات الروديوم و مقارنتها بالنتائج التجريبية

الملخص EN

This work focus on theoretical studies by DFT/B3LYP that is in order to determine the mechanism of transition between two isomers of Rh (III) CpRh (SiR2R') (H) (C2H4) (R2R'= H3, Me3) and then compared with experimental results.

The structure and the infrared spectrum of the intermediate state between two isomers were identified.

Results of structure of intermediate state obtained indicate to the existence of bond of type η2-Si–H, and the length of the Si-H bond was about 1.6 Å.

Spectroscopic study insist that the intermediate state is transition state due to the presence of imaginary frequency .

It was found as well the following values of ΔS = 7.6 kJ / mol , ΔH = 65.4 kJ / mol, ΔG = 62.9 kJ/mol which were obtained by calculating the parameters of activation transitional state of the complex CpRh (SiMe3) (H) (C2H4).

These values were in a very good agreement with the following experimental values of the complex CpRh (SiMe3) (H) (C2H3CO2tBu), ΔS = 12 ± 9 kJ / mol, ΔH = 61.9 ± 3 kJ / mol, ΔG = 58.9 ± 0.1 kJ / mol.

Based on the results of the theoretical study it can be concluded that the transition between two isomers are made through forming a complex transitional contain the bond type η2-Si-H followed by a rotation around the Si –H bond.