Simple Ligand Effects Switch a Hydrogenase Mimic between H2 and O2 Activation

Simple Ligand Effects Switch a Hydrogenase Mimic between H2 and O2 Activation:

Abstract

Herein, we report a [NiRu] biomimetic system for O₂-tolerant [NiFe]hydrogenases and demonstrate that electron donation to the [NiRu] center can switch the system between the activation of H₂ and O₂ through simple ligand effects by using hexamethylbenzene and pentamethylcyclopentadienyl ligands, respectively. Furthermore, we present the synthesis and direct observations of a [NiRu]–peroxo species, which was formed by the oxygenation of a Ni-SIa model [NiRu] complex, that we propose as a biomimetic analogue of O₂-bound species (OBS) of O₂-tolerant [NiFe]hydrogenases. The [NiRu]–peroxo complex was fully characterized by X-ray analysis, X-ray photoelectron spectroscopy (XPS), mass spectrometry, and ¹H NMR spectroscopy. The OBS analogue was capable of oxidizing p-hydroquinone and sodium borohydride to turn back into the Ni-SIa model complex.

At the flick of a switch: A [NiRu] biomimetic system for O₂-tolerant [NiFe]hydrogenases was constructed. Electron donation to the [NiRu] center switched the system between activation of H₂ and O₂. Furthermore, a [NiRu]–peroxo species, which was capable of oxidizing p-hydroquinone, was considered as a biomimetic analogue of O₂-bound species (OBS) of O₂-tolerant [NiFe]hydrogenases.