Open AccessAn [Fe4S4]3+–Alkyl Cluster Stabilized by an Expanded Scorpionate Ligand
Author(s) -
Alex McSkimming,
Arun Sridharan,
Niklas B. Thompson,
Péter Müller,
Daniel L. M. Suess
Publication year - 2020
Publication title -
journal of the american chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.115
H-Index - 612
eISSN - 1520-5126
pISSN - 0002-7863
DOI - 10.1021/jacs.0c06334
Subject(s) - chemistry , alkyl , ligand (biochemistry) , alkylation , cluster (spacecraft) , covalent bond , valence (chemistry) , stereochemistry , crystallography , organic chemistry , catalysis , computer science , programming language , biochemistry , receptor
Alkyl-ligated iron-sulfur clusters in the [Fe 4 S 4 ] 3+ charge state have been proposed as short-lived intermediates in a number of enzymatic reactions. To better understand the properties of these intermediates, we have prepared and characterized the first synthetic [Fe 4 S 4 ] 3+ -alkyl cluster. Isolation of this highly reactive species was made possible by the development of an expanded scorpionate ligand suited to the encapsulation of cuboidal clusters. Like the proposed enzymatic intermediates, this synthetic [Fe 4 S 4 ] 3+ -alkyl cluster adopts an S = 1 / 2 ground state with g iso > 2. Mössbauer spectroscopic studies reveal that the alkylated Fe has an unusually low isomer shift, which reflects the highly covalent Fe-C bond and the localization of Fe 3+ at the alkylated site in the solid state. Paramagnetic 1 H NMR studies establish that this valence localization persists in solution at physiologically relevant temperatures, an effect that has not been observed for [Fe 4 S 4 ] 3+ clusters outside of a protein. These findings establish the unusual electronic-structure effects imparted by the strong-field alkyl ligand and lay the foundation for understanding the electronic structures of [Fe 4 S 4 ] 3+ -alkyl intermediates in biology.