Iron complexes ligand exchange reactions

Butler, A. R., Glidewell, C., Hyde, A. R., and Walton, J. C. (1985). Formation of paramagnetic mononuclear iron nitrosyl complexes from diamagnetic di- and tetranuclear iron-sulphur nitrosyls Characterization by EPR spectroscopy and study of thiolate and nitrosyl ligand exchange reactions. Polyhedron 4, 797-809. 

Xanthene and 6-thiaxanthene complexes of iron, 102 (X = O, S) are prepared by the ligand exchange reaction between the heterocycle and ferrocene (86JOM(305)199). Chemical oxidation using potassium permanganate leads to the ketones 103 (X = O, S). In the case of X = S, sulfone 104 is also obtained. 

In microbial iron assimilation, one mechanism for the release of iron from siderophores is the enzymatic reduction to the Fe state. Siderophore stability constants are much lower for Fe +, which has a lower charge-to-radius ratio. Moreover, ligand exchange reactions for the high-spin Fe ion are much faster than for the Fe ion. Stability constants of ferrous siderophores are experimentally difficult to obtain. Limiting pH-independent redox potentials can be utilized, however, to describe the electrochemical and chemical equilibria between fidly coordinated Fe + and Fe +-siderophore complexes and the uncomplexed Fe(H20)6 + and Fe(H20)e +, respectively, in a simple model as described in equation (5) ... 

The preparation of substituted pentacyanoferrate(II) ion complexes involves a series of ligand exchange reactions at the iron(II) metal center. Equations (4.1)-(4.3) outline the synthesis of amino acid (AA) metal complexes in aqueous solution. Starting from sodium nitroprusside ion, [Fe(CN)5(NO)]2, equation (4.1), the nitrosyl ligand, NO+, is replaced by an ammine moiety, NH3. The aquapentacyanoferrate(II) ion, [Fe(CN)5(H20)]3, is then generated in situ, equation (4.2), followed by reaction with an AA to yield the desired [Fe(CN)5(AA)](3+n) complex, equation (4.3). 

This complex can also be prepared by the ligand exchange reaction of (T M-phenyl-3-buten-2-one)(tricarbonyl)iron with 1,4-butadiene as described below [82]. 

Most of the olefin complexes examined in this study exhibit an unspectacular reactivity towards molecular oxygen, i. e. either ligand exchange reactions, 0-0-bond activation by highly oxophilic metals Sc, Ti, and V, or even complete absence of any reaction are observed (eg. even Cu(C2H4) is unreactive). However, in the case of the iron complexes extensive oxidation reactions are observed. Indeed, not only olefins attached to an iron cation react effectively with molecular oxygen, even stable molecules like benzene and acetone are rapidly oxidized in the presence of Fe+. 

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