Prebiotic chemistry: The formation of CH4 and NH3 from HCN is mediated by mackinawite oxidation to greigite in H2O. The reaction products were clearly identified by their isotopic shifts, using a GC-MS. In accordance with the experimental results a reaction mechanism, including the deprotonated mackinawite surface groups, is proposed.
Mackinawite has unique structural properties and reactivities when compared to other iron sulfides. Herein we provide evidence for the mackinawite-supported reduction of KCN into various reduced compounds under primordial conditions. We proposed a reaction mechanism based on the nucleophilic attack by the deprotonated mackinawite -SH surface groups at the carbon atom of HCN. The initial binding of the substrate and the subsequent reduction events are supported by DFT calculations and further experiments using other substrates, such as KSCN, KOCN and CS2. Until now, conversion of CN− into CH4 and NH3 has been limited to nitrogenase cofactors or molecular Fe-CN complexes. Our study provides evidence for mackinawite-supported cleavage of the C−N bond under ambient conditions, which opens new avenues for investigation of other substrates for mackinawite-supported reactions while shedding light on the relevance of this type of reaction to the origin of life on Earth.Zum Volltext