[Fe6Se9(SR)2]4- Clusters (R = Me, CH2Ph): Synthesis and Characterization, and the X-Ray Structure of (PhCH2NEt3)4[Fe6Se9(SMe)2]

Abstract

(1) The compounds (PhCH2NEt3)4[Fe6Se9(SMe)2] and (Et4N)4[Fe6Se9(SCH2Ph)2] (2) have been isolated in good yields from Fe(SR)3 (R = Me, CH2Ph)/“Na2Se2” reaction mixtures in methanol/N,N-dimethylformamide after addition of the appropriate tetraalkylammonium chlorides. 1 is monoclinic, space group P21/c, Z = 4, with a = 18.697(14), b - 22.606(16), c = 15.989(11) Å, and β = 94.15(6)° at 140 K. Its structure has been refined to R (Rw) = 0.092 (0.075). The [Fe6Se9(SMe)2]4- anion contains six coplanar iron atoms which are present in distorted tetrahedral Se4 and Se3(SMe) ligand surroundings. The Se atoms are μ, μ3 and μ4 bridging. The four central Fe atoms and the Se atoms constitute a Fe4Se9 group that is structurally related to 1 ∞[Fe2Se3]2- double tetrahedral chains and 2 ∞[FeSe] layers. The Fe atoms in the [Fe6Se9(SMe)2]4- cluster are antiferromagnetically coupled. 1 has a room-temperature magnetic moment of 1.22 μB/Fe. Cyclic voltammograms, and electronic, infrared, and proton resonance spectra of 1 and 2 have been measured.