Recent research towards development of more efficient as well as cost effective catalyst as a substitute to traditional precious metal catalysts has witnessed significant growth and interest. Importance has been given to catalyst based on 3d-transition metals, especially iron because of the broad availability and environmental compatibility which allows its use in various environmentally friendly catalytic processes. N-Heterocyclic carbene (NHC) ligands have garnered significant attention because of their unique steric and electronic properties which provide substantial scope and potential in organometallic chemistry, catalysis and materials sciences. In the context of catalytic applications, iron-NHC complexes have gained increasing interest in the past two decades and could successfully be applied as catalysts in various homogeneous reactions including C–C couplings (including biaryl cross-coupling, alkyl-alkyl cross-coupling, alkyl-aryl cross-coupling), reductions and oxidations. In addition to this, iron-NHC complexes have shown the ability to facilitate a variety of reactions including C-heteroatom bond formation reactions, hydrogenation and transfer-hydrogenation reactions, polymerization reactions, etc. In this chapter, we will discuss briefly recent advancements in the catalytic activity of iron-NHC complexes including mono-NHC, bis-NHC (bidentate), tripodal NHC and tetrapodal NHC ligands. We have chosen iron-NHC complexes because of the plethora of publications available, increasing significance, being more readily available, non-toxic and economical.
Part of the book: Organic Synthesis