Taming the Dichalcogenides: Isolation, Characterization, and Reactivity of Elusive Perselenide, Persulfide, Thioselenide, and Selenosulfide Anions

摘要

Reactive sulfur species (RSS) andreactive selenium species(RSeS)play integral roles in hydrogen sulfide (H2S) and hydrogenselenide (H2Se) biological signaling pathways, and dichalcogenideanions are proposed transient intermediates that facilitate a varietyof biochemical transformations. Herein we report the selective synthesis,isolation, spectroscopic and structural characterization, and fundamentalreactivity of persulfide (RSS-), perselenide (RSeSe-), thioselenide (RSSe-), and selenosulfide(RSeS-) anions. The isolated chalcogenides do notrely on steric protection for stability and have steric profiles analogousto cysteine (Cys). Simple reduction of S-8 or Se by potassiumbenzyl thiolate (KSBn) or selenolate (KSeBn) in the presence of 18-crown-6afforded K(18-crown-6)BnSS (1), K(18-crown-6)BnSeSe(2), K(18-crown-6BnSSe (3), and K(18-crown-6BnSeS(4). The chemical structure of each dichalcogenide wasconfirmed by X-ray crystallography and solution-state H-1, C-13, and Se-77 NMR spectroscopy. To advanceour understanding of the reactivity of these species, we demonstratedthat reduction of 1-4 by PPh3 readily generates EPPh3 (E: S, Se), and reduction of 1, 3, and 4 by DTT readily produces HE-/H2E. Furthermore, 1-4 react with CN- toproduce ECN-, which is consistent with the detoxifyingeffects of dichalcogenide intermediates in the Rhodanese enzyme. Takentogether, this work provides new insights into the inherent structuraland reactivity characteristics of dichalcogenides relevant to biologyand advances our understanding of the fundamental properties of thesereactive anions.