Hightlight Paper

The Mechanism of Irdium(III) Catalyzed CO₂ Hydrogenation

We have studied the mechanism of the iridium(III) catalyzed hydrogenation of CO₂ in aqueous base. The reaction was reported by Nozaki and co-workers in 2009 and showed an extraordinary turnover number (TON) and turnover frequency (TOF). Hydrogenation of carbon dioxide has been proposed as a viable way of storing H₂. While methanol is the most desired product from such hydrogenation, it is quite demanding for a catalyst to hydrogenate both CO₂ and all the intermediates before methanol efficiently.

The results from the computational study showed that the catalytic cycle is initiated by the reaction between the iridium(III) hydride and CO₂, which proceeds with a relatively low barrier. The reaction is calculated to be endergonic by 2 kcal/mol, which is in good agreement with experiments where both the trihydride complex and the formate complex were observed simultaneously under an atmosphere of CO₂. The rate limiting step was found to be the regeneration of the trihydride, and the overall barrier for the reaction was calculated to 26 kcal/mol.

Reference

Ahlquist M. S. G J. Mol. Cat. A. , Article ASAP doi:10.1016/j.molcata.2010.02.018

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