Interconversion between [Fe₄S₄] and [Fe₂S₂] Clusters Bearing Amide Ligands

Abstract

Structural conversion of [Fe4S4] clusters into [Fe2S2] clusters has been suggested to be a fundamental process for some O2-sensing proteins. While the formation of [Fe2S2] clusters from synthetic [Fe4S4] clusters has been unprecedented, an all-ferric [Fe4S4](4+) cluster Fe4S4{N(SiMe3)2}4 (1) was found to split in the presence of pyridines, giving [Fe2S2] clusters Fe2S2{N(SiMe3)2}2(L)2 (2, L = pyridines). The structural conversion between [Fe4S4] and [Fe2S2] clusters appeared to be reversible, and the thermodynamic parameters for the equilibrium reactions between 1 + L and 2 were determined. Assembly of two [Fe2S2] clusters was also induced by chemical reductions of Fe2S2{N(SiMe3)2}2(Py)2 (Py = pyridine), and the resultant [Fe4S4] clusters [1](-) and [1](2-) were found to split into two [Fe2S2] clusters by oxidation with [Cp2Fe](+) in the presence of pyridine.

An [Fe4S4]3+–Alkyl Cluster Stabilized by an Expanded Scorpionate Ligand

“…These preliminary results and the aforementioned enzymatic studies suggested that [Fe 4 S 4 ] 3+ –alkyl clusters may be exceptionally reactive. Indeed, synthetic [Fe 4 S 4 ] 3+ clusters are generally more difficult to isolate than [Fe 4 S 4 ] 2+ clusters, and, to date, only a handful have been reported. − Consequently, we sought a new strategy for isolating an [Fe 4 S 4 ] 3+ –alkyl cluster. We reasoned that incorporation of a noncoordinating anion into a tridentate ligand framework would allow for the generation of an [Fe 4 S 4 ] 3+ –alkyl cluster as a monocation instead of a dication, with the decreased molecular charge rendering the cluster less electrophilic.…”

Controlled Generation of 9‐Boratriptycene by Lewis Adduct Dissociation: Accessing a Non‐Planar Triarylborane

“…The molecular structures of 16 – 19 in the solid state were determined by single‐crystal X‐ray diffraction (Figures and ). The B−N distance in 17 (1.594(2) Å) is shorter than in the pyridine−B(C 6 F 5 ) 3 Lewis adduct (1.614(2) Å) and similar to that in the pyridine Lewis adduct 4 (1.584(2) Å), which is one of the shortest B−N bond lengths reported with a neutral boron Lewis acid.…”

“…Steric repulsions between the boratriptycene peri‐hydrogen atoms and the pyridine moiety caused its deviation by a tilt angle β of 15° from the triptycene central B⋅⋅⋅C axis (Figures c,d). The pyramidalization angle α in 17 (23.8°) is higher than in the Lewis adducts of pyridine with B(C 6 F 5 ) 3 (17.6°) or 1‐boraadamantane (20.0°) and comparable to that in the borabarrelene adduct 5 (24.5°) …”

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

“…Systematic work by Agapie has demonstrated electronic and catalytic modulation of iron cluster sites with interstitial light atoms [11, 12] . An incredibly thorough and long‐standing research program by Tatsumi has yielded highly complex iron‐sulfur structures of multiple nuclearities, [13–15] which include structures bearing an interstitial sulfide as found in the nitrogenase P‐cluster [16, 17] and a structure containing an interstitial oxide [18] . In a similar vein, the Holm group reported an iron‐sulfur cluster that incorporates a silyl‐nitride into the cluster core [19] .…”