Functionalization of N2 by Mid to Late Transition Metals via N-N Bond Cleavage

This review focuses on the recent efforts to functionalize dinitrogen via complete cleavage of the N N bond with particular emphasis on mid to late transition metal complexes. The relationships of electronic and structural parameters for the most common N-2-bonding modes (end-on and side-on bridging) with N-2-splitting reactivity are discussed. This analysis points towards electronic configurations with pi(10) (end-on) and pi(8)delta(2) (side-on) electrons within the M2N2-cores for full N-N bond cleavage into terminal and bridging nitride complexes, respectively. The full body of work on N-2-splitting with group 6-8 metals is comprehensively presented. Ligand electronic and steric effects are discussed in detail for privileged platforms, such as low coordinate, electron rich complexes with pi-donating ligands. Finally, several strategies for functionalization of the nitrides resulting from N-2-splitting are presented that lead to N-C bond formation. The developed pseudocatalytic cycles reported so far that combine N-2-cleavage, nitride functionalization, and N-transfer provide guidelines for rational catalyst design.