Orbital interactions in 1, n-dithia[ n]ferrocenophanes; a He(I) photoelectron spectroscopic study

Abstract

The He(I) photoelectron specta of 1, n-dithia[ n]ferrocenophanes ( n = 3–8, 10) and 1,1′-bis(methylthio)ferrocene are reported. The energy gap between the 2 A 1( a 1 1 e 2 4) and 2 E 2( a′ 1 2 e′ 2 3) ion states is decreased by the perturbation of the coplanarity of ligand planes and by a conjugative interaction of sulphur lone pairs with ferrocene orbitals. The inverse dependence of the two effects of the length of the interligand bridge leads to the observed minimal gap for n = 5. The splitting of sulphur lone pairs in the spectra reveals a strong interaction, the nature of which depends on the length of the interligand bridge. The “angle-determining” sulphur p-orbitals are split by a through-bond interaction if n = 3–5. The highest occupied π-orbitals of ferrocene relay the through-bond interaction of the orbitals localized on sulphur.