Synthesis and crystal structure of 1,1′,2,2′-bis(1,2,3-trithia-[3])ferrocenophane

Abstract

The first multiply chalcogen-bridged metallocene compound 1,1′,2,2′-bis(1,2,3-trithia-[3])ferrocenophane 1, a species featuring two S₃ linkages around the metallocene nucleus, has been prepared by the lithiation of ferrocene 1,1′-dithiol, followed by treatment with elemental sulfur. The sulfur linkages lie in adjacent positions on the cyclopentadienyl rings and, in solution, the compound exists as a mixture of two diastereomers due to the orientation of the trisulfur bridges. Proton NMR spectra at ambient temperatures indicate the predominance of the chair–chair isomer 1a(70%) over the less-favoured chair–boat species 1b(30%). The structure of 1 has been determined by X-ray diffraction and the crystals are monoclinic, space group P2₁/n with a= 6.830(1), b= 13.310(1), c= 13.929(1)Å, β= 99.70(1)° and Z= 4. Least-squares refinement give R= 0.030 for 1650 observed reflections whose intensities were measured on an area detector diffractometer with Mo-K_α radiation. The S–S bond lengths are 2.054(4), 2.065(4), 2.044(4) and 2.054(4)Å and the S(1)–S(2)–S(3) and S(4)–S(5)–S(6) bond angles are 105.1(2) and 103.5(2)° respectively. The S–C bond lengths are 1.752(6), 1.760(6), 1.752(6) and 1.755(6)Å with S–S–C bond angles of 102.3(2), 102.2(2), 102.4(3) and 101.8(2)°. The cyclopentadienyl rings are in an eclipsed conformation and are mutually parallel. The trisulfide linkages are in a chair–chair conformation with non-bonding separation of 3.25 and 3.23 Å for S(1)⋯ S(3) and S(4)⋯ S(6) respectively.