Low-Spin Pseudotetrahedral Iron(I) Sites in Fe2(μ-S) Complexes

Authors

  • John S. Anderson,

    1. Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125 (USA)
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  • Prof. Jonas C. Peters

    Corresponding author
    1. Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125 (USA)
    • Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125 (USA)===

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  • This research was supported by the NIH (GM 070757). J.S.A. gratefully acknowledges a GRFP award from the NSF. Po-Heng Lin, Jay Winkler, Bruce Brunschwig, Harry Gray, and Dave Harris are thanked for helpful discussions.

Abstract

FeI centers in iron–sulfide complexes have little precedent in synthetic chemistry despite a growing interest in the possible role of unusually low valent iron in metalloenzymes that feature iron–sulfur clusters. A series of three diiron [(L3Fe)2(μ-S)] complexes that were isolated and characterized in the low-valent oxidation states FeII[BOND]S[BOND]FeII, FeII[BOND]S[BOND]FeI, and FeI[BOND]S[BOND]FeI is described. This family of iron sulfides constitutes a unique redox series comprising three nearly isostructural but electronically distinct Fe2(μ-S) species. Combined structural, magnetic, and spectroscopic studies provided strong evidence that the pseudotetrahedral iron centers undergo a transition to low-spin S=1/2 states upon reduction from FeII to FeI. The possibility of accessing low-spin, pseudotetrahedral FeI sites compatible with S2− as a ligand was previously unknown.

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