A new preorganized tridentate ligand bearing three indolethiolate groups. Preparation of 3:1 subsite-differentiated Fe4S4 clusters

1,3,5-Triethyl-2,4,6-tris(3-sulfanylindoyl[1]methyl)benzene (TriSH(3)) has been prepared in three steps from 3-sulfanylindole and 1,3,5-tris(bromomethyl)-2,4,6-triethylbenzene. X-Ray analysis and NMR spectroscopy demonstrated it is highly preorganized for co-ordination to three subsites of a Fe4S4 cluster core. The clusters [PPh4](2)[Fe4S4(Tris)(Br)] and [PPh4](2)[Fe4S4(TriS)(SPh)] were obtained by reaction of [PPh4](2)[Fe4S4(SEt)(4)] with TriSH(3) under dynamic vacuum followed by addition of [(Me2N)(2)CSSC(NMe2)(2)]Br-2 and substitution of bromide with PhS- respectively. The latter was characterized by X-ray structure analysis. No crystallographic symmetry is imposed on the cluster anion and the cluster core exhibits the tetragonal distortion typical of tetrathiolate-substituted Fe4S4 cores. This implies that the trithiolate ligand TriS(3-) is sufficiently rigid to guarantee co-ordination to a single cluster core, while it is still flexible enough to match the preferred core distortions.