Crystal structure and carbon-13 nuclear magnetic resonance spectrum of [NMe4]2[Fe4S4(SCH2CH2OH)4] and electron spin resonance spectrum of [Fe4S4(SCH2CH2OH)4]3– in aqueous solution
Abstract
The compound [NMe4]2[Fe4S4(SCH2CH2OH)4] is triclinic, space group P, with a= 10.686(9), b= 11.288(8), c= 15.021(11)Å, α= 99.0(1), β= 91.8(1), γ= 108.4(1)°, and Z= 2. 2 115 Independent reflections measured on a diffractometer have been refined to R= 0.088. The anion contains the Fe4S4 cubane-like cluster core distorted from Td symmetry such that four approximately parallel Fe–S bonds are shorter (mean 2.239 Å) than the other eight (mean 2.306 Å). There are two strong intermolecular O ⋯ H–O hydrogen bonds (O ⋯ O 2.63, 2.70 Å) and there may be an intermolecular S ⋯ H–O hydrogen bond(S ⋯ O 3.16 Å). Carbon-13 n.m.r. (90 MHz) spectra have been recorded for the title compound in dimethyl sulphoxide solution between 317 and 363 K; the resonance position of thiolate carbon was observed between 103.3 and 106.4 p.p.m. downfield of SiMe4. The anion [Fe4S4(SCH2CH2OH)4]3–, generated by dithionite treatment of the title compound in buffered aqueous solution containing excess of 2-hydroxyethanethiol and stabilised by rapid freezing, exhibits an axially symmetric e.s.r. spectrum with g∥= 2.045 and g⊥= 1.929 (= 1.967); similar treatment of the title compound with K3[Fe(CN)6] also generated a species having an axially symmetric e.s.r. spectrum, with g∥= 1.963 and g⊥= 2.006.