Simple ligand effects switch a hydrogenase mimic between H2 and O2 activation

Herein, we report a [NiRu] biomimetic system for O(2)-tolerant [NiFe]hydrogenases and demonstrate that electron donation to the [NiRu] center can switch the system between the activation of H(2) and O(2) 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 O(2)-bound species (OBS) of O(2)-tolerant [NiFe]hydrogenases. The [NiRu]-peroxo complex was fully characterized by X-ray analysis, X-ray photoelectron spectroscopy (XPS), mass spectrometry, and (1)H NMR spectroscopy. The OBS analogue was capable of oxidizing p-hydroquinone and sodium borohydride to turn back into the Ni-SIa model complex.