Mechanistic Studies on NaHCO 3 Hydrogenation and HCOOH Dehydrogenation Reactions Catalysed by a Fe II Linear Tetraphosphine Complex.

Authors :: Marcos R
Bertini F
Rinkevicius Z
Peruzzini M
Gonsalvi L
Ahlquist MSG
Source :: Chemistry (Weinheim an der Bergstrasse, Germany) [Chemistry] 2018 Apr 06; Vol. 24 (20), pp. 5366-5372. Date of Electronic Publication: 2018 Jan 24.
Publication Year :: 2018
Abstract: We present a theoretical extension of the previously published bicarbonate hydrogenation to formate and formic acid dehydrogenation catalysed by Fe <superscript>II</superscript> complexes bearing the linear tetraphosphine ligand tetraphos-1. The hydrogenation reaction was found to proceed at the singlet surface with two competing pathways: A) H <subscript>2</subscript> association to the Fe-H species followed by deprotonation to give a Fe(H) <subscript>2</subscript> intermediate, which then reacts with CO <subscript>2</subscript> to give formate. B) CO <subscript>2</subscript> insertion into the Fe-H bond, followed by H <subscript>2</subscript> association and subsequent deprotonation. B was found to be slightly preferred with an activation energy of 22.8 kcal mol <superscript>-1</superscript> , compared to 25.3 for A. Further we have reassigned the Fe-H complex, as a Fe(H)(H <subscript>2</subscript> ), which undergoes extremely rapid hydrogen exchange.<br /> (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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