Alkylidyne and Alkylidene Complexes of Iron

Alkylidyne and alkylidene ligands constitute cornerstones of organometallic chemistry. Accordingly, a large variety of related iron complexes has been reported in the last five decades. In this chapter, the synthesis, the properties, the spectroscopic and structural features, and the reactivity of alkylidyne and alkylidene ligands coordinated in iron complexes will be presented and discussed. Since these two types of ligands manifest markedly different behaviors according to the nature of their substituents and the nuclearity of the related compounds, monoiron, diiron and then polyiron species will be treated separately, and different sections will be dedicated to ligands lacking or bearing hetero-substituents. Concerning those families of compounds for which much progress has been made in recent times, the discussion will be limited to the literature since 2000 onwards. Only a brief overview will be finally traced of iron-NHC complexes, an impressively expanding field for which references will be given to recent key reviews.