We describe rhenium(I) triscarbonyl compounds (3 and 4) decorated with simple-to-use 2-iminomethyl-pyridine (1, impy) and 2-aminomethyl-pyridine (2, ampy) ligands, respectively, which can serve as cooperative ligand scaffolds enabling CO 2 binding via a formal [1,3] addition under Re−O and C−C bond formation. fac-[Re(impy)-(CO) 3 Br] (3) is readily prepared by stirring (1-(pyridin-2yl)-N-(p-tolyl)methanimine (impy, 1) and [Re(CO ) 5 Br] in refluxing THF. Alternatively, complex 3 can be readily obtained when a mixture of [Re(CO) 5 Br], p-toluidine, and picolinaldehyde is refluxed in ethanol. Complex 3 is reduced with excess potassium metal in THF (two-electron reduction) to give the anionic amido complex K[Re(amidopy*)(CO) 3 ] (5b, the asterisk indicates the dearomatized ligand). Analysis of the 1 H and 13 C{ 1 H} NMR spectra of 5b suggest the dearomatization of the pyridine unit. Complex 5b is highly reactive and gives rise to the facile [1,3] addition of CO 2 . The addition of the CO 2 and thus the formation of K[Re(amidopy-COO)(CO) 3 ] ( 6) is characterized by the concomitant formation of a Re−O and a C−C bond. The addition is triggered by the rearomatization of the pyridine unit in 6. Remarkably, isotopic labeling experiments involving 13 CO 2 suggest a reversible binding of CO 2 to the complex. The related amine complex fac-[Re(ampy)(CO) 3 Br] (4) is similarly prepared by stirring (4-methyl-N-(pyridin-2ylmethyl)aniline ( 2) and [Re(CO) 5 Br] in THF at 60 °C. Upon addition of excess base (LiHMDS), complex 3 is readily deprotonated twice to give likewise the anionic amido complex Li[Re(amidopy*)(CO) 3 ] (5a). The latter reaction gives rise to a facile access to the reactive dearomatized anionic fragment [Re(amidopy*)(CO) 3 ] − with no need for the application of strong reducing agents. The ion pair M + /[Re(amidopy*)(CO) 3 ] − is highly reactive and combines MLC (metal−ligand cooperation) via a dearomatization/rearomatization scheme and bifunctional reactivity enabled by the nucleophilic nature of the Re complex and the Lewis acidic counter alkali cation.
The electrochemical nitrogen oxidation reaction (NOR) has recently drawn attention due to promising experimental and theoretical results. It provides an alternative, environmentally friendly route to directly synthesize nitrate from N 2 (g). There is to date a limited number of investigations focused on the electrochemical NOR. Herein, we present a detailed computational study on the kinetics of both the NOR and the competing oxygen evolution reaction (OER) on the TiO 2 (110) electrode under ambient conditions. The use of grand canonical density functional theory in combination with the linearized Poisson−Boltzmann equation allows a continuous tuning of the explicitly applied electrical potential. We find that the OER may either promote or suppress the NOR on TiO 2 (110) depending on reaction conditions. The detailed atomistic insights provided on the mechanisms of these competing processes make possible further developments toward a direct electrochemical NOR process.
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