Prospects and challenges for nitrogen-atom transfer catalysis

Conversion of C–H bonds to C–N bonds via C–H amination promises to streamline the synthesis of nitrogen-containing compounds. Nitrogen-group transfer (NGT) from metal nitrenes ([M]–NR complexes) has been the focus of intense research and development. By contrast, potentially complementary nitrogen-atom transfer (NAT) chemistry, in which a terminal metal nitride (an [M]–N complex) engages with a C–H bond, is underdeveloped. Although the earliest examples of stoichiometric NAT chemistry were reported 25 years ago, catalytic protocols are only now beginning to emerge. Here, we summarize the current state of the art in NAT chemistry and discuss opportunities and challenges for its development. We highlight the synthetic complementarity of NGT and NAT and discuss critical aspects of nitride electronic structure that dictate the philicity of the metal-supported nitrogen atom. We also examine the characteristic reactivity of metal nitrides and present emerging strategies and remaining obstacles to harnessing NAT for selective, catalytic nitrogenation of unfunctionalized organic small molecules. Here, the utility of nitrogen-atom transfer chemistry is highlighted, the aspects that dictate nitride philicity discussed, and the reactivity of metal nitrides towards substrate functionalization examined. Emerging strategies and the remaining obstacles to harnessing nitrogen-atom transfer for nitrogenation of organic small molecules are presented.