79466-67-4Relevant academic research and scientific papers
Ligand substitution properties of the MFe3S4 double-cubane cluster complexes [Mo2Fe6S8(SR)9]3- and [M2Fe7S8(SR)12]3- (M = Mo, W)
Palermo,Power,Holm
, p. 173 - 181 (2008/10/08)
Reactions of the double-cubane clusters [Mo2Fe6S8(SEt)9]3- (1) and [M2Fe7S8(SEt)12]3- (3, M = Mo, W) with benzenethiol and acetyl chloride have been investigated in order to ascertain ligand substitution propensities of thiolate ligands. These complexes contain individual MoFe3S4(SEt)3 clusters connected by (μ-SEt)3 or (μ-SEt)3FeIII(μ-SEt)3 bridging groups and thus offer as potential reaction sites both terminal and bridging thiolate sulfur atoms. Reactions of 1 with 1-6 and larger equiv of reagent were monitored by UV-visible spectrophotometry, 1H NMR spectroscopy, and differential-pulse polarography. The limiting substituted species formed were [Mo2Fe6S8(μ-SEt)3(SPh) 6]3- (5) and [Mo2Fe6S8(μ-SEt)3Cl 6]3- (4), salts of which were isolated in good yield when reactions with ?6 equiv of reagent were conducted on a preparative scale. Preparative reactions of 3 and ?6 equiv of reagent afforded isolated salts of [Mo2Fe7S8(μ2-SEt) 6(SPh)6]3- (8) and [M2Fe7S8(μ-SEt)6Cl 6]3- (7). Similarly, [W2Fe6S9(SEt)8]3- (2) yielded [W2Fe6S8(μ-S)(μ-SEt) 2(S-P-tol)6]3- (6) with p-toluenethiol. Structures of all products are fully documented by spectroscopic and electrochemical properties. These results lead to the conclusion that the two electrophilic reagents effect only terminal ligand substitution under reaction conditions (Me2SO or acetonitrile solutions, ambient temperature, stoichiometric or (specified) excess of reagent) that leave intact individual cluster structures A reported exception to this consistent reactivity pattern, viz., formation of [Mo2Fe6S8(SCH2CH2OH) 9]3- from the reaction of 1 with excess 2-hydroxyethanethiol, was not confirmed. By comparison of properties of authentic [Mo2Fe6S8-(SCH2CH 2OH)9]3-, prepared by direct synthesis, the ligand exchange product isolated in this work was shown to be [Mo2Fe6S8(μ-SEt)3(SCH 2CH2OH)6]3-. The bridge structure of the precursor cluster is retained, as in the formation of 4-8 by similar reactions.
