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Synthesis and X-ray Crystal Structure of a Cationic Homoleptic (SPS)2Rh(III) Complex and EPR Study of Its Reduction Process

Doux, Marjolaine
Mézailles, Nicolas
Ricard, Louis
Le Floch, Pascal
Published in Inorganic Chemistry. 2005, vol. 44, no. 4, p. 1147-1152
Abstract Oxidation of the square planar Rh(I) complex [Rh(SPSMe)(PPh3)] (SPSMe = 1-methyl-1-P-2,6-bis(diphenylphosphinosulfide)-3,5-(bisphenyl)-phosphinine) (1) based on mixed SPS-pincer ligand with hexachloroethane yielded the Rh(III) dichloride complex [Rh(SPSMe)(PPh3)Cl2] (2), which was structurally characterized. The homoleptic Rh(III) complex [Rh(SPSMe)2][Cl] (4) was obtained via the stoichiometric reaction of SPSMe anion (3) with [Rh(tht)3Cl3] (tht = tetrahydrothiophene). Complex 4, which was characterized by X-ray diffraction, was also studied by cyclic voltammetry. Complex 4 can be reversibly reduced at E = −1.16 V (vs SCE) to give the neutral 19-electron Rh(II) complex [Rh(SPSMe)2] (5). Accordingly, complex 5 could be synthesized via chemical reduction of 4 with zinc dust. EPR spectra of complex 5 were obtained after electrochemical or chemical reduction of 4 in THF or CH2Cl2. Hyperfine interaction with two equivalent 31P nuclei was observed in liquid solution, while an additional coupling with a spin 1/2 nucleus, probably 103Rh, was detected in frozen solution. The 31P couplings are consistent with DFT calculations that predict a drastic increase in the axial P−S bond lengths when reducing (SPSMe)2Rh(III). In the reduced complex, the unpaired electron is mainly localized in a rhodium dz2 orbital, consistent with the g-anisotropy measured at 100 K.
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Research group Groupe Geoffroy
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DOUX, Marjolaine et al. Synthesis and X-ray Crystal Structure of a Cationic Homoleptic (SPS)2Rh(III) Complex and EPR Study of Its Reduction Process. In: Inorganic Chemistry, 2005, vol. 44, n° 4, p. 1147-1152. https://archive-ouverte.unige.ch/unige:3627

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Deposited on : 2009-10-02

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