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{C5H5-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.