Homogeneous iron complexes for the conversion of dinitrogen into ammonia and hydrazine

One of the most challenging problems in small molecule activation is the development of a homogeneous catalyst for converting dinitrogen into ammonia at ambient temperatures and atmospheric pressure. A catalytic cycle based on molybdenum that converts dinitrogen into ammonia has been reported. However, a well defined iron based system for the conversion of dinitrogen into ammonia or hydrazine has remained elusive, despite the relevance of iron to biological nitrogen fixation. In recent years several research groups have made significant progress towards this target. This tutorial review provides a brief historical perspective on attempts to develop iron based catalysts for dinitrogen functionalisation and then focuses on recent breakthroughs in the chemistry of coordinated dinitrogen, such as the generation of ammonia and hydrazine from coordinated dinitrogen, the isolation and characterisation of several proposed intermediates for ammonia generation and some preliminary mechanistic conclusions.