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

Abstract

1,3,5-Triethyl-2,4,6-tris(3-sulfanylindolyl[1]methyl)benzene (TriSH₃) 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 TriSH₃ under dynamic vacuum followed by addition of [(Me₂N)₂CSSC(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.

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