Cation and ligand roles in the coordination of FeIII bisdithiolene complexes; the crystal structures of (BrBzPy)2[Fe(qdt)2]2 and [Fe(α-tpdt)2]22− salts

Abstract

The crystal structure of the new (BrBzPy)₂[Fe(qdt)₂]₂ complex (qdt = quinoxalinedithiolate) shows a rare weak Fe^III bisdithiolene dimerisation with unusual molecular planarity and long apical S–Fe distances. This anion configuration is intermediate between the only monomeric Fe bisdithiolene reported so far, with isolated square planar [Fe(qdt)₂]⁻ units, and the common strong dimeric geometry also observed in other [Fe(qdt)₂]₂ salts. The standard strong dimeric situation is also observed in the [Fe(α-tpdt)₂]₂ salt (α-tpdt = 2,3-thiophenedithiolate) with the same cation, as well as with n-Bu₄N and Et₄N showing the influence of different ligands and cations on the coordination geometry and supramolecular structure of the Fe^III complexes.