The reaction between FeCl2, (C6H5)4PCl, and KSC6H5 in acetonitrile in at 2:1:3 molar ratio or between [Fe(SC6H5)4]2− and FeX2 (X = Cl, Br) in a 1:2.4 molar ratio affords in excellent yields the new [Fe4(SC6H5)6X4]2− clusters. The paramagnetic [(C6H5)4P]2[Fe4(SC6H5)6Cl4] (I) crystallizes in the triclinic space group P1̄ with two molecules in the unit cell. The cell dimensions are a = 23.122 (6) Å, b = 13.986 (1) Å, c = 14.189 (4) A, α = 73.65 (1)∘, β = 80.58 (1)∘, and γ = 84.91 (1)∘. Intensity data were collected with a four-circle computer-controlled diffractometer with use of the θ–2θ step scan technique. All of the nonhydrogen atoms in the anion and the two phosphorus atoms in the cations were refined with anisotropic temperature factors while the carbon atoms in the (C6H5)P+ cations were refined with isotropic temperature factors. Refinement by full-matrix least squares of 661 parameters on 5514 data gave a final R value of 0.074. The hydrogen atoms were included in the structure factor calculation but were not refined. The overall description of the Fe4S6Cl4 core in I is that of a nearly regular Fe4 tetrahedron inscribed in a slightly irregular octahedron defined by the bridging S atoms in an “adamantane” type of cage. The four chlorine atoms coordinated one on each of the four iron atoms define an outer tetrahedron such that the overall symmetry of the Fe4S6Cl4 unit is very nearly Td. Average values of selected structural parameters and the estimated standard deviations calculated from scatter of values around the mean are Fe—Fe = 3.94 (4) Å, Fe—S = 2.362 (15) Å, Fe—Cl = 2.254 (3) Å, S—S = 3.79 (2) Å, S—Cl = 3.82 (7) Å; Fe—Fe—Fe = 60 (1)∘, Fe—S—C = 108.3 (25), Cl—Fe—S = 112 (3), S—Fe—S = 107 (7)∘, Fe—S—Fe = 113 (2)∘. Distortions in each of the four tetrahedral ClFeIIS3 units can be explained in terms of phenyl ring repulsions on the periphery of the Fe4S6 cage. The reactions of dibenzyl trisulfide with I in ratios that do not exceed 2, in either CH3CN or CH3CN/HCON(CH3)2 mixtures, afford the new mixed ligand “cubane” [(C6H5)4P]2[Fe4S4(SC6H5)2Cl2] (II) in very good yields. The chemical and physical properties including electrochemical properties and proton magnetic resonance spectra as well as preliminary X-ray crystallographic results confirm the identity of II. In reactions where the dibenzyl trisulfide to I ratio exceeds 4, the [Fe4S4Cl4]2− (III) “cubane”-type cluster forms and can be isolated in excellent yields when the reagent ratio is 8:1.
ASJC Scopus subject areas
- Colloid and Surface Chemistry