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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

Published inInorganic chemistry, vol. 44, no. 4, p. 1147-1152
Publication date2005
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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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. doi: 10.1021/ic049046+
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