Electrochemical and Chemical Reductions to Stable [Co(NO)]9 N-Confused Porphyrin Complexes for NO to Nitrous Oxide Conversion

Abstract

Stable [Co(NO)]9 complex is rare in literature. In this report, we present the synthesis of a [Co(NO)]8 N-confused porphyrin (NCP) complex from the reaction of a four coordinated cobalt complex with nitric oxide. In addition to the regular N-confused porphyrin ligand, the [Co(NO)]8 complexes with an inner carbon methylated NCP and inner carbon oxygenated NCP were also obtained. Reversible redox couples were observed from CV and IR spectroelectrochemical studies upon the electrochemical reduction or oxidation on the [Co(NO)]8 complexes. The distinctive differences on the shifting of ν(NO) suggest that the supporting ligand will control an either metal-based or a ligand-based redox process. Through a bulk electrolysis or treatment of cobaltocene, [Co(NO)]9 complexes were obtained. The obtain of the first single-crystal structure further demonstrates an unique stability of this NCP ligand supported [Co(NO)]9 complex. For the first time, we observed that the [Co(NO)]9 complex is active toward the hydrogen evolution reaction. More importantly, the addition of ethanol into the solution of [Co(NO)]9 observed the conversion of axial NO ligand to nitrous oxide. The potential mechanism of NO to N2O conversion and the spectroscopic information of the reaction intermediates will be discussed in this presentation. Figure 1