Standard Article

Nitrogenase: Metal Cluster Models

  1. Frédéric Barrière

Published Online: 15 MAR 2006

DOI: 10.1002/0470862106.ia158

Encyclopedia of Inorganic Chemistry

Encyclopedia of Inorganic Chemistry

How to Cite

Barrière, F. 2006. Nitrogenase: Metal Cluster Models. Encyclopedia of Inorganic Chemistry. .

Author Information

  1. Université de Rennes 1, Institut de Chimie, Rennes, France

Publication History

  1. Published Online: 15 MAR 2006

Abstract

This article reviews the synthesis and properties of inorganic clusters that model the iron–sulfur centers found in the nitrogenase enzyme. These sites are of the Fe4S4, Fe8S7, and MoFe7S9 stoichiometry. The enzyme [Fe4S4]2+/1+ center is well modeled by synthetic clusters bearing thiolate ligands at iron. However, the [Fe4S4]0 state is stabilized in the enzyme and has not been reproduced in the laboratory so far. Recent progress in synthetic models of the Fe8S7 P-cluster is reported. One of its known structures can be obtained by self-assembly from basic constituents, or synthesized in a stepwise fashion from smaller clusters yielding topological analogues. The most challenging cluster to model is the FeMo-cofactor. This MoFe7S9 center is the site of dinitrogen reduction to ammonia. The cluster also exists with vanadium or iron in place of molybdenum in alternative nitrogenases. It was shown only recently that the FeMo-cofactor is centered on a light atom that is probably a nitrogen atom. Structural modeling of this center is limited. Only its molybdenum or heterometal end has been accurately modeled. Functional chemistry of good structural models, those with sulfur ligands and metal–metal bonds, only concerns the reduction of already partially reduced diazo substrates such as diazene or hydrazine.

Keywords:

  • nitrogenase;
  • iron–sulfur clusters;
  • nitrogen fixation;
  • molybdenum;
  • iron;
  • vanadium;
  • sulfur;
  • FeMo-cofactor;
  • P-cluster;
  • dinitrogen complexes