1006630-19-8Relevant articles and documents
RhCl3-assisted C-H and C-S bond scissions: Isomeric self-association of organorhodium(III) thiolato complex. Synthesis, structure, and electrochemistry
Pramanik, Kausikisankar,Das, Ujjwal,Adhikari, Basab,Chopra, Deepak,Stoeckli-Evans, Helen
, p. 429 - 438 (2008/10/09)
The ligating properties of alkyl 2-(phenylazo)phenyl thioether 1 (HL R; R = Me, CH2Ph) toward Rh(III) have been examined. A novel hexacoordinated orthometalated rhodium(III) thiolato complex trans-[Rh(L)Cl(PPh3)2] 5 has been synthesized from 1 and RhCl3·3H2O in the presence of excess PPh 3 via in situ C(sp2)-H and C(sp3)-S bond scissions, which is the first example for a coordination compound of [L] 2-. We were also able to isolate the intermediate organothioether rhodium(III) compound trans-[Rh(LR)Cl2(PPh3)] 6 with 1 equiv of PPh3 relative to both 1 and RhCl3· 3H2O in the course of the synthesis of the S-dealkylated product. PPh3 plays a crucial role in the C(sp3)-S cleavage process. A plausible mechanistic pathway is presented for C-S bond cleavage, and reductive cleavage by single-electron transfer mechanism is likely to be operative. The electronically and coordinatively saturated thiolato complex 5, indefinitely stable in the solid state, undergoes spontaneous self-dimerization in solution via dissociation of one coordinated PPh3 molecule to afford edge-shared bioctahedral anti-[Rh(L)Cl(PPh3)]2 7 and syn-[Rh(L)Cl(PPh3)]2 8 isomers. All the synthesized organosulfur rhodium(III) compounds were isolated as both air- and moisture-stable solids and spectroscopically characterized in both solution and solid states. In addition, all the representative members have been authenticated by single-crystal X-ray structure analyses. Availability of the isomeric dimers provides an opportunity to recognize the presence of noncovalent intramolecular metallochelate-metallochelate interaction in the sterically encumbered syn isomer. Unlike other organosulfur rhodium complexes, the monomelic thiolato complex 5 exhibits a fully reversible oxidative wave at 0.82 V vs Ag/AgCl, which is supposed to be primarily centered on the thiolato sulfur atom, and such perception is consistent with the DFT study. Formation of rhodium-bound thiyl radical cation 5?+ by electrochemical oxidation was scrutinized by EPR spectroscopy.
