Rhodium(III) and Ruthenium(II) Complexes of a Redox-Active N-Heterocyclic Carbene/Thioether Ligand

Agnès LABANDE , ^a,* Jean-Claude DARAN, a Nicholas J. LONG, b Andrew J. P. WHITE, ^b Rinaldo POLI ^a,c

a: CNRS; LCC (Laboratoire de Chimie de Coordination); 205, route de Narbonne, 31077 Toulouse cedex 4, France and Université de Toulouse; UPS, INPT; 31077 Toulouse, France;

b: Department of Chemistry, Imperial College London, London, SW7 2AZ, United Kingdom ; c: Institut Universitaire de France, 103, bd Saint-Michel, 75005 Paris, France.

E-mail: agnes.labande@lcc-toulouse.fr

The electronic properties of a ligand can easily be changed by the introduction of electroactive functionalities. This has been demonstrated in the field of small molecule sensing [1] and in catalysis [2]. In the latter domain, transition metal complexes containing redox-active ligands have shown charge-dependent behaviour.

Half-sandwich rhodium(III) and ruthenium(II) complexes bearing a new redox-active ferrocenyl NHC-thioether ligand have been prepared. The synthesis of the ferrocenyl thioether-imidazolium salt, precursor of the NHC ligand, was carried out via the intermediate 2-chloroethylthioferrocene using an improved procedure [3]. The rhodium(III) complex and the ruthenium(II) complex were obtained in good yields and were fully characterised by NMR spectroscopy, X-ray diffraction analysis and electrochemistry. The rhodium(III) complex shows a complex ABCD system by 1H NMR, which denotes conformational rigidity due to the presence of several bulky groups. Electrochemical analysis by cyclic voltammetry reveals reversible redox behaviour about the iron centre in both complexes.

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