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S/N crosstalk species derived from the interconnected reactivity of H₂S and NO facilitate the transport of reactive sulfur and nitrogen species in signaling, transport, and regulatory processes. We report here that simple Fe²⁺ions, such as those that are bioavailable in the labile iron pool (LIP), react with thionitrite (SNO⁻) and perthionitrite (SSNO⁻) to yield the dinitrosyl iron complex [Fe(NO)₂(S₅)]⁻. In the reaction of FeCl₂with SNO⁻we were able to isolate the unstable intermediate hydrosulfido mononitrosyl iron complex [FeCl₂(NO)(SH)]⁻, which was characterized by X‐ray crystallography. We also show that [Fe(NO)₂(S₅)]⁻is a simple synthon for nitrosylated Fe−S clusters via its reduction with PPh₃to yield Roussin's Red Salt ([Fe₂S₂(NO)₄]²⁻), which highlights the role of S/N crosstalk species in the assembly of fundamental Fe−S motifs.

 

The short C–H⋯S contacts found in available structural data for both small molecules and larger biomolecular systems suggest that such contacts are an often overlooked yet important stabilizing interaction. Moreover, many of these short C–H⋯S contacts meet the definition of a hydrogen bonding interaction. Using available structural data from the Cambridge Structural Database (CSD), as well as selected examples from the literature in which important C–H⋯S contacts may have been overlooked, we highlight the generality of C–H⋯S hydrogen bonding as an important stabilizing interaction. To uncover and establish the generality of these interactions, we compare C–H⋯S contacts with other traditional hydrogen bond donors and acceptors as well as investigate how coordination number and metal bonding affect the preferred geometry of interactions in the solid state. This work establishes that the C–H⋯S bond meets the definition of a hydrogen bond and serves as a guide to identify C–H⋯S hydrogen bonds in diverse systems. 

We highlight a convenient synthesis to selectively deuterate an aryl C–H hydrogen bond donor in an arylethynyl bisurea supramolecular anion receptor and use the Perrin method of competitive titrations to study the deuterium equilibrium isotope effects (DEIE) of anion binding for HS − , Cl − , and Br − . This work highlights the utility and also challenges in using this method to determine EIE with highly reactive and/or weakly binding anions.