Single‐Step Sulfur Insertions into Iron Carbide Carbonyl Clusters: Unlocking the Synthetic Door to FeMoco Analogues

Abstract

The one‐step syntheses, X‐ray structures, and spectroscopic characterization of synthetic iron clusters, bearing either inorganic sulfides or thiolate with interstitial carbide motifs, are reported. Treatment of iron carbide carbonyl clusters [Fen(μn‐C)(CO)m]x (n=5,6; m=15,16; x=0,−2) with electrophilic sulfur sources (S2Cl2, S8) results in the formation of several μ4‐S dimers of clusters, and moreover, iron‐sulfide‐(sulfocarbide) clusters. The core sulfocarbide unit {C−S}4− serves as a structural model for a proposed intermediate in the radical S‐adenosyl‐L‐methionine biogenesis of the M‐cluster. Furthermore, the electrophilic sulfur strategy has been extended to provide the first ever thiolato‐iron‐carbide complex: an analogous reaction with toluylsulfenyl chloride affords the cluster [Fe5(μ5‐C)(SC7H7)(CO)13]−. The strategy described herein provides a breakthrough towards developing syntheses of biomimetic iron‐sulfur‐carbide clusters like FeMoco.

Structure, reactivity, and spectroscopy of nitrogenase-related synthetic and biological clusters

“…Both Rauchfuss and Rose have recently isolated iron carbonyl clusters with central carbides and sulfides as the ligands. [98][99][100][101] However, these clusters all contain low-valent, low-spin iron and thus are not of direct electronic structural relevance to FeMo-cofactor. While thus far it has not been possible to fuse two iron sulfur cubanes with a carbide (as realized in the biosynthesis of FeMo-cofactor 47,102 ), synthetic chemists have attempted to approach this question in a more stepwise fashion utilizing high-spin iron sites which are electronically analogous to those in FeMo-cofactor and incorporating light atoms into dinuclear and larger clusters.…”

Cluster Models of FeMoco with Sulfide and Carbyne Ligands: Effect of Interstitial Atom in Nitrogenase Active Site

“…Figure 1: Top: Structure of FeMoco in Mo-dependent nitrogenase from PDB structure 3U7Q with blue circle emphasizing the cubane subsite and its schematic representation highlighting in color the subsite of focus in this study; bottom: carbyne and carbide containing model complexes. [9][10][11]…”

Construction of Synthetic Models for Nitrogenase-Relevant NifB Biogenesis Intermediates and Iron-Carbide-Sulfide Clusters

“…As such, a synthetic strategy centered around S 2 Cl 2 was deemed appropriate for sulfide incorporation [67]. While SCl 2 is more structurally analogous to SO 2 (Figure 7), the reported instability of the reagent and its spontaneous conversion to S 2 Cl 2 marked it as less preferable.…”