Tetrathiafulvalene–phosphine-based iron and ruthenium carbonyl complexes: Electrochemical and EPR studies

Cyril Gouverd; Frédéric Biaso; Laurent Cataldo; Théo Berclaz; Michel Geoffroy; Eric Levillain; Narcis Avarvari; Marc Fourmigué; François X. Sauvage; Corinne Wartelle

doi:10.1039/B409958C

Tetrathiafulvalene–phosphine-based iron and ruthenium carbonyl complexes: Electrochemical and EPR studies†

Cyril Gouverd,^a Frédéric Biaso,^a Laurent Cataldo,^a Théo Berclaz,^a Michel Geoffroy,*^a Eric Levillain,^b Narcis Avarvari,*^b Marc Fourmigué,^b François X. Sauvage^c and Corinne Wartelle^c

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* Corresponding authors

^a Department of Physical Chemistry, University of Geneva, 30 Quai Ernest Ansermet, Geneva, Switzerland
E-mail: Michel.Geoffroy@chiphy.unige.ch

^b Laboratoire “Chimie, Ingénierie Moléculaire et Matériaux” (CIMMA), UMR 6200 CNRS-Université d’Angers, UFR Sciences, 2 Bd. Lavoisier, Bât. K, Angers Cedex, France
E-mail: narcis.avarvari@univ-angers.fr

^c LASIR-HEI, CNRS UMR 8516, 13 rue de Toul, Lille Cedex, France

Abstract

The radical cation of the redox active ligand 3,4-dimethyl-3′,4′-bis-(diphenylphosphino)-tetrathiafulvalene (P2) has been chemically and electrochemically generated and studied by EPR spectroscopy. Consistent with DFT calculations, the observed hyperfine structure (septet due to the two methyl groups) indicates a strong delocalization of the unpaired electron on the central S₂C [double bond, length as m-dash] CS₂ part of the tetrathiafulvalene (TTF) moiety and zero spin densities on the phosphine groups. In contrast with the ruthenium(0) carbonyl complexes of P2 whose one-electron oxidation directly leads to decomplexation and produces P2˙⁺, one-electron oxidation of [Fe(P2)(CO)₃] gives rise to the metal-centered oxidation species [Fe^(I)(P2)(CO)₃], characterized by a coupling with two ³¹P nuclei and a rather large g-anisotropy. The stability of this complex is however modest and, after some minutes, the species resulting from the scission of a P–Fe bond is detected. Moreover, in presence of free ligand, [Fe^(I)(P2)(CO)₃] reacts to give the complex [Fe^(I)(P2)₂(CO)] containing two TTF fragments. The two-electron oxidation of [Fe(P2)(CO)₃] leads to decomplexation and to the P2˙⁺ spectrum. Besides EPR spectroscopy, cyclic voltammetry as well as FTIR spectroelectrochemistry are used in order to explain the behaviour of [Fe(P2)(CO)₃] upon oxidation. This behaviour notably differs from that of the Ru(0) counterpart. This difference is tentatively rationalized on the basis of structural arguments.

Physical Chemistry Chemical Physics

Tetrathiafulvalene–phosphine-based iron and ruthenium carbonyl complexes: Electrochemical and EPR studies†

Abstract

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Tetrathiafulvalene–phosphine-based iron and ruthenium carbonyl complexes: Electrochemical and EPR studies

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