Brief survey of diiron and monoiron carbonyl complexes and their potentials as CO-releasing molecules (CORMs)

Iron carbonyl complexes are a large category of classic transition metal complexes. In addition to their vast range of applications in catalysis, they have been found to be of therapeutic applications. One of the therapeutic applications is that upon appropriate external stimulations, iron carbonyl complexes release CO which is found to be a gasotransmittter in human body and a beneficial molecule playing various physiological and pathological roles. This review is mainly concerned with diiron and monoiron carbonyl complexes, and their applications as CO-releasing molecules (CORMs). One section (Section 2) is briefly devoted to those homoleptic iron(0) carbonyl complexes since they are frequently employed as the precursors in preparing other iron carbonyl complexes. Section 3 is for diiron carbonyl complexes and only those complexes closely related to the mimics of the diiron subunit of [FeFe]-hydrogenase are discussed in the order of hexa-, penta- and tetracarbonyl. In Section 4, monoiron carbonyl complexes are discussed according to their oxidation states from -II to IV while the categorisation by number of the bound CO is also considered. Section 5 is devoted to CORMs and the research status of each category of the iron carbonyl complexes covered in this review as CORMs is summarised. And finally, the perspectives of iron carbonyl complexes as therapeutic agents and those categories of iron carbonyl complexes of great potentials in this regard are also discussed. (C) 2020 Elsevier B.V. All rights reserved.