Computational Design of Iron Diphosphine Complexes with Pendant Amines for Hydrogenation of CO₂ to Methanol: A Mimic of [NiFe] Hydrogenase

Abstract

Inspired by the active-site structure of the [NiFe] hydrogenase, we have computationally designed the iron complex [P(tBu) 2 N(tBu) 2 )Fe(CN)2 CO] by using an experimentally ready-made diphosphine ligand with pendant amines for the hydrogenation of CO2 to methanol. Density functional theory calculations indicate that the rate-determining step in the whole catalytic reaction is the direct hydride transfer from the Fe center to the carbon atom in the formic acid with a total free energy barrier of 28.4 kcal mol(-1) in aqueous solution. Such a barrier indicates that the designed iron complex is a promising low-cost catalyst for the formation of methanol from CO2 and H2 under mild conditions. The key role of the diphosphine ligand with pendent amine groups in the reaction is the assistance of the cleavage of H2 by forming a Fe-H(δ-) ⋅⋅⋅H(δ+) -N dihydrogen bond in a fashion of frustrated Lewis pairs.

Computational Design of Quaterpyridine‐Based Fe/Mn–Complexes for the Direct Hydrogenation of CO2 to HCOOH: A Direction for Atom‐Economic Approach

“…Also recall that, an axial ligand with a more σ ‐donor capacity can substantially reduce such barrier . Here, the Fe‐qtpy complex with La=PMe 3 requires only 12.24 kcal/mol of energy for overcoming the TS 3,4 barrier which is also comparable to that of the pendant amine‐based Fe complex, a mimic of [NiFe]‐hydrogenase as reported recently by Chen et al . As the Figure and Table show, the added base has a substantial effect on the kinetic barrier of proton and hydride transfer processes, may be due to difference in basicity and degree of solvation, however, the base‐free condition might be an alternative route for avoiding the rigorousness of the reaction.…”

Mechanistic Insights and Computational Design of Transition‐Metal Catalysts for Hydrogenation and Dehydrogenation Reactions

“…Later, they confirmed the existence of the Fe−H δ− ···H δ+ −N dihydrogen bond in [Cp C5F4N FeH( H)] + using single‐crystal neutron diffraction 45b. Inspired by the above findings and the active‐site structure of [FeFe]‐ and [NiFe]‐hydrogenases, we proposed a series of iron diphosphine complexes incorporated with pendant amines (Figure ), ( )Fe(CN) 2 CO46 and ( )FeH(CO) 2 R47 (R=H, Cl, NO 2 , CN, C 5 H 4 N, CH 3 , NH 2 , OCH 3 , OH, CHO, COOH, COCH 3 , COOCH 3 , CONH 2 , and CONHCOOH), and predicted their potentials as efficient catalysts for the hydrogenation of CO 2 to methanol.…”

Biomimetic heterobimetallic architecture of Ni(ii) and Fe(ii) for CO2 hydrogenation in aqueous media. A DFT study

“…[36][37][38][39][40][41] The mechanistic studies of CO 2 hydrogenation through DFT studies has revealed that either abstraction of hydride from the metal center or heterolytic cleavage of coordinated H 2 over the metal center is usually the rate-determining step of entire catalytic cycle. [36][37][38][39] The barrier height for H 2 heterolytic cleavage can be signicantly reduced by introducing a base in catalyst and one of such example is hydrogen oxidation catalyst reported by Bullock and co-workers containing pendant amine as base. 42 Likewise, the signicant role of base in heterolytic cleavage of coordinated H 2 has also been reported in other studies as well.…”