Thionitrite (SNO - ) and Perthionitrite (SSNO - ) are Simple Synthons for Nitrosylated Iron Sulfur Clusters.

S/N crosstalk species derived from the interconnected reactivity of H 2 S and NO facilitate the transport of reactive sulfur and nitrogen species in signaling, transport, and regulatory processes. We report here that simple Fe 2+ 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 (S 5 )] - . In the reaction of FeCl 2 with SNO - we were able to isolate the unstable intermediate hydrosulfido mononitrosyl iron complex [FeCl 2 (NO)(SH)] - , which was characterized by X-ray crystallography. We also show that [Fe(NO) 2 (S 5 )] - is a simple synthon for nitrosylated Fe-S clusters via its reduction with PPh 3 to yield Roussin's Red Salt ([Fe 2 S 2 (NO) 4 ] 2- ), which highlights the role of S/N crosstalk species in the assembly of fundamental Fe-S motifs.