Dinitrogen Activation and Functionalization with Chromium
Alexander J. Kendall, Michael T. Mock
Abstract
The study of metal‐dinitrogen complexes has lent valuable insight into the nature of dinitrogen (N 2 ) reduction to ammonia (NH 3 ), known as “nitrogen fixation.” Even so, understanding this difficult transformation continues to be an elusive goal for chemists. The N 2 chemistry of chromium (Cr) is exceptional for its diversity, rarity, and richness of depth. Hans Karsch opined in 1977 that “ Almost all transition metals are known to form complexes with molecular nitrogen, but in the case of some metals ‐ notably chromium ‐ the examples are few and far between .” Although that sentiment hasn't changed much in 42 years, recent advances in the field of Cr‐N 2 chemistry have begun to illuminate that elusive relationship. Herein we cover the theory and experimental basis for chromium's coordination, activation, reduction, and catalysis of N 2 to NH 3 . An emphasis will be placed on work towards understanding catalytic systems for chromium mediated dinitrogen reduction.