82616-29-3Relevant articles and documents
Synthetic route to [Fe6S9(SR)2]4- clusters (R = alkyl). Their spectroscopic and magnetic properties and the solid-state structures of [Fe6S9(SCH2Ph)2]4- and [(Fe6S9(SMe)2)2Na2] 6-
Strasdeit, Henry,Krebs, Bernt,Henkel, Gerald
, p. 1816 - 1825 (2008/10/08)
The hexanuclear iron-sulfide-thiolate complexes [Fe6S9(SR)2]4- (R = Me, Et, CH2Ph) have been prepared in methanolic solution by reaction of Fe(SR)3 with Na2S2 and were isolated as black, air-sensitive crystals of (Et4N)4[Fe6S9(SCH 2Ph)2]·H2O (1), (Et4N)4[Fe6S9(SEt)2] (2), and (Et4N)6[(Fe6S9(SMe) 2)2Na2] (3). The crystal and molecular structures of 1 and 3 have been determined from three-dimensional X-ray data. 1 crystallizes in the monoclinic space group P21/c with a = 16.339 (3) A?, b = 19.535 (4) A?, c = 21.729 (4) A?, β = 106.56 (3)°, and Z = 4. Crystals of 3 were found to be monoclinic, space group C2/m, with a = 12.813 (13) A?, b = 28.626 (21) A?, c = 16.056 (17) A?, β = 129.06 (7)°, and Z = 2. The structures were solved by direct methods and refined to conventional R factors of 0.060 and 0.085, respectively. Crystals of 1 and 3 consist of discrete anions, cations, and, in the case of 1, H2O molecules. The [Fe6S9(SCH2Ph)2]4- anion possesses a nearly planar arrangement of the Fe atoms resulting from a coupling of six FeS4 tetrahedra via common edges and corners. Structural characteristics of the [Fe6S9]2- core are Fe3S7 and Fe4S9 fragments, which represent subunits of the well-known cubane-type [Fe4S4(SR)4]2-,3- clusters and the hypothetical [Fe8S6(SR)8]n- cluster family with a cubic arrangement of Fe atoms respectively. [Fe7MoS6(SR)7Ln]z-, a mixed-metal derivative, is supported as a structural and compositional model for the Mo-Fe center of nitrogenase. The Fe3S7 fragment is discussed in connection with the 3-Fe center of Desulfovibrio gigas ferredoxin II and beef heart aconitase. The structure of the novel [(Fe6S9(SMe)2)2Na2] 6- anion in crystals of 3 can be described in terms of two hexanuclear iron-sulfide-thiolate units that are connected by two sodium cations or, alternatively, in terms of four [Fe3NaS4(SR)6]5- units condensed via adjacent sodium and sulfur corners. Temperature-dependent solid-state magnetic susceptibility data of 1 are qualitatively consistent with antiferromagnetic coupling of the Fe atoms within the cluster and a diamagnetic ground state below 20 K. The position of the isotropically shifted S-CH2 1NMR signal of 1 between 225 and 340 K was measured as well as the room-temperature 1H NMR spectra of 2 and 3 and the infrared and electronic spectra of 1, 2, and 3. For iron-sulfide-thiolate clusters an empirical correlation between the composition and the mean oxidation state of iron is given.
