Mechanistic study of CO/CO2 conversion catalyzed by a biomimetic Ni(II)iminothiolate complex

Funding information AFOSR, Grant/Award Number: FA9550-170198; National Science Foundation, Grant/ Award Number: CNS08-21132; NSF Graduate Research Fellowship, Grant/Award Number: DGE-1122492 Abstract We investigate the CO oxidation into CO2 catalyzed by a biomimetic Ni(II)-iminothiolate complex in the presence of the sacrificial oxidizing agent methylviologen. We propose a catalytic mechanism supported by the density functional theory analysis of reaction intermediates that agrees with available experimental observations and kinetic data. We rule out a fivecoordinate Ni(II) species as well as a Ni(III) intermediate which was previously proposed and instead identify a key four-coordinate Ni(II) carbonyl species. We find that the turnoverlimiting step is likely the formation of the Ni(II) carboxylic acid species, although if a worse oxidant were used or if the concentration was less, then the oxidation of the Ni(I) species would be the turnover-limiting step. The reported findings should enable the design of better catalysts to favor one of the two competing pathways for CO to CO2 conversion as catalyzed by this particular complex.