[NiIII(OMe)]-mediated reductive activation of CO2 affording a Ni(κ1-OCO) complex

Abstract

Carbon dioxide is expected to be employed as an inexpensive and potential feedstock of C₁ sources for the mass production of valuable chemicals and fuel. Versatile chemical transformations of CO₂, i.e. insertion of CO₂ producing bicarbonate/acetate/formate, cleavage of CO₂ yielding μ-CO/μ-oxo transition-metal complexes, and electrocatalytic reduction of CO₂ affording CO/HCOOH/CH₃OH/CH₄/C₂H₄/oxalate were well documented. Herein, we report a novel pathway for the reductive activation of CO₂ by the [Ni^III(OMe)(P(C₆H₃-3-SiMe₃-2-S)₃)]⁻ complex, yielding the [Ni^III(κ¹-OCO˙⁻)(P(C₆H₃-3-SiMe₃-2-S)₃)]⁻ complex. The formation of this unusual Ni^III(κ¹-OCO˙⁻) complex was characterized by single-crystal X-ray diffraction, EPR, IR, SQUID, Ni/S K-edge X-ray absorption spectroscopy, and Ni valence-to-core X-ray emission spectroscopy. The inertness of the analogous complexes [Ni^III(SPh)], [Ni^II(CO)], and [Ni^II(N₂H₄)] toward CO₂, in contrast, demonstrates that the ionic [Ni^III(OMe)] core attracts the binding of weak σ-donor CO₂ and triggers the subsequent reduction of CO₂ by the nucleophilic [OMe]⁻ in the immediate vicinity. This metal–ligand cooperative activation of CO₂ may open a novel pathway promoting the subsequent incorporation of CO₂ in the buildup of functionalized products.