Tetrathiafulvalene-phosphine-based iron and ruthenium carbonyl complexes: electrochemical and EPR studies.
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=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.
Gouverd
Cyril
C
Department of Physical Chemistry, University of Geneva, Geneva, Switzerland.
Biaso
Frédéric
F
Cataldo
Laurent
L
Berclaz
Théo
T
Geoffroy
Michel
M
Levillain
Eric
E
Avarvari
Narcis
N
Fourmigué
Marc
M
Sauvage
François X
FX
Wartelle
Corinne
C
D018360:Crystallography, X-Ray; D004572:Electrolysis; D004574:Electromagnetic Fields; D004578:Electron Spin Resonance Spectroscopy; D006571:Heterocyclic Compounds / Q000737:chemistry*; D054354:Iron Carbonyl Compounds / Q000737:chemistry*; D007502:Iron Chelating Agents / Q000737:chemistry; D008670:Metals; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D012428:Ruthenium / Q000737:chemistry*
D006571:Heterocyclic Compounds; D007502:Iron Chelating Agents; D008670:Metals; D054354:Iron Carbonyl Compounds; D012428:Ruthenium; C063887:tetrathiafulvalene