Electron and Hydride Transfer in a Redox-Active NiFe Hydride Complex: A DFT Study

Abstract

We present mechanistic details of the formation of a NiFe hydride complex and provide information on its electron-and hydride-transfer processes on the basis of density functional theory calculations and artificial-forceinduced-reaction studies. The NiFe hydride complex conducts three transfer reactions: namely, electron transfer, hydride transfer, and proton transfer. In a NiFe hydride complex, the hydride binds to Fe, which is different from the Ni−R state in hydrogenase where the hydride is located between Ni and Fe. According to our calculations, in reaction with the ferrocenium ion, electron transfer occurs from the NiFe hydride complex to the ferrocenium ion, followed by a hydrogen atom transfer (HAT) to the second ferrocenium ion. The oxidation state of Fe varies during the redox process, different from the case of NiFe hydrogenase, where the oxidation state of Ni varies. A single-step hydride transfer occurs in the presence of a 10-methylacridinium ion (AcrH + ), which is more kinetically feasible than the HAT process. In contrast to the HAT and hydride-transfer process, the proton transfer occurs through a low barrier from a protonated diethyl ether. The revealed reaction mechanism guides the interpretation of the catalytic cycle of NiFe hydrogenase and leads to the development of efficient biomimetic catalysts for H 2 generation and an electron/hydride transfer.

H2activation by hydrogenase-inspired NiFe catalyst using frustrated Lewis pair: effect of buffer and halide ion in the heterolytic H–H bond cleavage

“…The revealed mechanism is similar to H 2 activation by NiFe–CH 3 CN and NiIr–Cl complexes ( Fig. 8a–c ) previously investigated using DFT, 40,51 where ‘CH 3 CN’ in NiFe–CH 3 CN and ‘H 2 O’ in NiIr–H 2 O represent the coordination species in the active catalytic site Fe and Ir, respectively. In all three complexes, dihydrogen is activated using a frustrating Lewis pair.…”

[NiFe], [FeFe], and [Fe] hydrogenase models from isomers

“…The BP86 functional has been used to model biomimetic NiFe complexes (26)(27)(28)(29). Furthermore, in our previously studied analogical NiFe complexes, the BP86 functional correctly described the ground-state spin multiplicity, while two hybrid functionals, B3LYP-D3 (D3-corrected Becke three-parameter Lee-Yang-Parr functional) (23,30) and TPSSh (Tao-Perdew-Staroverov-Scuseria) (31), failed to predict (32,33). Thus, the choice of BP86 functional is appropriate.…”

Synthetic Designs and Structural Investigations of Biomimetic Ni–Fe Thiolates

“…3 They are all of the type L 2 Ni(SR) 2 FeHL 3 . In these models the Fe-H bond is usually 8 shorter than the Ni-H bond, [9][10][11][12] whereas in the enzyme, the d Ni-H < d Fe-H . 13 The shorter Ni-H distance underscores the role of Ni as the hydride carrier, whereas Fe center serves as a redox-inactive Lewis acid.…”