Nitrogen oxyanion deoxygenation: Redox chemistry and oxygen atom transfer reactions

Though unintended, anthropogenic nitrogen fixation on the global scale offsets the natural nitrogen cycle. Emissions of nitrogen oxides from the combustion of fossil fuels and leakage of ammonia from fertilizer-ladened land contributes to a substantial increase in reactive nitrogen content in the environment. Accumulation of nitrogen oxyanions in bodies of water has led to eutrophication and aquatic dead zones near coastal areas. The biological, environmental, and economic damage entailed must be addressed. To that end, artificial denitrification processes are necessary to combat looming environmental problems. In this review, a brief selection of literature on the reduction of nitrogen oxyanions, accomplished by transition metal complexes, is provided. Two broad categories of nitrogen oxyanion reduction are discussed: oxygen atom transfer (OAT) and electroreduction.