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Abstract Persulfides (RSS^–) and thioselenides (RSSe^–) play important roles in biological S and Se transfer reactions, and their interactions with Lewis acidic moieties exert control over reactivity. Here, we report the synthesis and reactivity of mononuclear Zn²⁺persulfide and thioselenide complexes from a unified synthetic strategy of using isolable dichalcogenide precursors. Highlighting the benefits of replacing S with Se, we use⁷⁷Se NMR spectroscopy to reveal the effects of Lewis acid coordination (K⁺, Na⁺, Zn²⁺) on the electronic environment of the terminal Se of the thioselenide (R–S_β–Se_α^–). Coordination of RSSe^–to Zn²⁺polarizes the Se─S bond, rendering the internal sulfur atom (R–S_β–Se_α^–) susceptible to nucleophilic attack and resulting in selenide (Se^2–) release. We also prepared a mononuclear Zn²⁺persulfide complex and probed differences in persulfide nucleophilicity when compared to the parent thiolate. Alkylation of the Zn²⁺persulfide is considerably faster than the Zn²⁺thiolate, supporting the proposed nucleophilicity enhancement of persulfides due to the α‐effect, and providing new insights into persulfide reactivity when coordinated to metals. Taken together, these investigations highlight the utility of small molecule synthetic models in advancing insights into the biological chemistry of metal dichaclogenides. 

Hydrogen selenide (H2Se) is an emerging bioregulator and precursor to essential selenium-containing biomolecules. We show that aryl isoselenocyanates (ISeC-R) release H2Se upon activation by cysteine, and that electronic substitution can modulate release profiles. We also demonstrate applications to live cell imaging, expanding available tools for investigating H2Se chemical biology. 

At ambient conditions, the high-entropy alloy superconductor R⁢e0.6⁢(NbTiZrHf)0.4 exhibits exceptional mechanical properties among high-entropy alloys, with its hexagonal phase achieving nanoindentation hardness of 18.5 GPa. We report on a unique pressure-induced structural transformation from a hexagonal phase to a body-centered cubic (BCC) phase, revealed by synchrotron x-ray diffraction measurements up to 70 GPa. This first-order transition, accompanied by a 6.1% volume collapse, occurs at 44 GPa and results in a BCC structure with random site occupancy by the five constituent elements, which is remarkably retained upon decompression to ambient conditions. The transformation proceeds via a martensiticlike, diffusionless mechanism without elemental segregation, enabled by pressure-induced electronic redistribution and atomic-scale disorder. These findings demonstrate a rare case of metastable phase retention in a chemically complex alloy and offer new insights into structure-stability relationships under pressure.