Molecular and crystal structures of six poly(arylsulfinyl)- and poly(arylsulfanyl)ferrocenes

Starting from (p-tolylsulfinyl)ferrocene (1), a mixture of the complete series [CpFe{C₅H_5-n(SOTol-p)_n}] (n = 2-4) (2-4) in all regioisomers was obtained. After chromatographic separation, crystals of 1,2-bis[(4-methylbenzene)sulfinyl]ferrocene, 2a, and 1,3-bis[(4-methylbenzene)sulfinyl]ferrocene, 2b, both [Fe(C₅H₅)(C₁₉H₁₇O₂S₂)], as well as of 1,2,3-tris[(4-methylbenzene)sulfinyl]ferrocene, [Fe(C₅H₅)(C₂₆H₂₃O₃S₃)], 3a, and 1,2,3,4-tetrakis[(4-methylbenzene)sulfinyl]ferrocene ethyl acetate 0.75-solvate, [Fe(C₅H₅)(C₃₃H₂₉O₄S₄)]·0.75C₄H₈O₂, 4, could be isolated. Their molecular and crystal structures are compared with each other and also with the so far unreported structures of related 1,2-bis(phenylsulfanyl)ferrocene, [Fe(C₅H₅)(C₁₇H₁₃S₂)], 5, and 1,2,3,4-tetrakis(phenylsulfanyl)ferrocene, [Fe(C₅H₅)(C₂₉H₂₁S₄)], 6. In all the sulfinyl structures, the O atoms of the S=O groups are in equatorial positions, except for that in tetrasubstituted 4. All the arene rings of these compounds (except for one ring in 4) are in axial positions directed away from the Fe atom, mostly in a near perpendicular orientation with respect to the plane of the cyclopentadienyl ring. The main intermolecular interactions in the crystals are C-H...H-C, C-H...π and C-H...O, while C-H...S interactions are much less important, except for tetrasulfanyl compound 6. π-π interactions (intramolecular) are only important in compound 3a. Hirshfeld analysis shows that dispersion terms are dominant for the interaction energies of all six compounds. In general, the calculated total interaction energies increase with increasing number of substituents and are higher for the sulfinyl than for the sulfanyl groups.