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Issue 18, 1996
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Characteristics of acid-catalysed substitution mechanisms and sites of protonation in iron–sulfur-based clusters, as revealed by studies on [Cl2FeS2VS2FeCl2]3–

Abstract

The kinetics of the non-catalysed and acid-catalysed substitution of the first two chloride ligands of [Cl2FeS2VS2FeCl2]3–, by 4-RC6H4S to form [(4-RC6H4S)ClFeS2VS2FeCl(SC6H4R-4)]3–(R = Cl, H, Me or MeO), has been studied in MeCN at 25.0 °C using stopped-flow spectrophotometry. Whereas the non-catalysed substitution occurs by a dissociative mechanism, the acid-catalysed substitution (using [NHEt3]+ as the acid) is associative. In the acid-catalysed mechanism the rate of substitution is maximised when protonation and binding of the nucleophile occur at adjacent sites. Two features of this study appear to be general for a range of structurally different iron–sulfur-based clusters: (1) the proton affinities of the clusters and (2) the acid-catalysed substitution mechanisms. These aspects are discussed for a variety of iron–sulfur-based clusters, including [(MoFe3S4Cl3)2{µ-Fe(SEt)6}]3–.

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J. Chem. Soc., Dalton Trans., 1996, 3667-3675
Article type
Paper

Characteristics of acid-catalysed substitution mechanisms and sites of protonation in iron–sulfur-based clusters, as revealed by studies on [Cl2FeS2VS2FeCl2]3–

K. L. C. Grönberg and R. A. Henderson, J. Chem. Soc., Dalton Trans., 1996, 3667
DOI: 10.1039/DT9960003667

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