Density functional theory study the reduction of carbon dioxide by terminal TaH complexes

The experiment study indicates that tantalaziridine-hydride ((Ar[tBuCH2]N)2(η2-tBu(H)CNAr)TaH) is able to convert to the isomeric hydride ((Ar[tBuCH2]N)2(κ2-CH2C(Me)2CH2NAr)TaH). And also, the both of tantalaziridine-hydride were found to be able to react with CO2 to give bimetallic methlene diolates. In this paper, the mechanism of the tautomerism had been investigated theoretically by DFT. The results reveal that this reaction is accomplished by two steps via tridentateligand intermediate. This kind of intermediate can be considered as the activating reagent to activate the CH bond. Further calculations showed that the reduction of CO2 with the terminal tantalum hydrides was carried out by two-step reaction mechanisms, via formate intermediate. In these studies, fully geometry optimized reactants, products, transition states, and intermediates were obtained.