An experimental and density functional study of the Sb–C bond activation and organo-Rh bond formation from the spontaneous decay of [RhCl3(SbPh3)3]

The reaction of RhCl₃ with SbPh₃ that produces mer-RhCl₃(SbPh₃)₃] 1 and trans,mer-RhCl₂(Ph)(SbPh₃)₃] 2 A. Cavaglioni, R. Cini, J. Chem. Soc., Dalton Trans. (1997) 1149 (and references cited therein)], as well as the transformation of 1 to 2, was studied in details using the UV–Vis spectroscopy and density functional approaches. We elucidated the mechanism of Sb–C(Ph) bond activation and Rh–C(Ph) bond formation during these processes. Experimental studies show that the first step of the reaction of RhCl₃ with SbPh₃ is the formation of 1, which later rearranges to complex 2 via a concerted mechanism. The transition state associated with this transformation includes the Rh(III) center (hepta-coordinate) that interacts with three Cl^? ligands, two Sb-centers of SbPh₃ ligands, and one Sb–Ph bond of the third SbPh₃ ligand. The Cl^? ligand, trans to Sb, bridges Rh and Sb atom from the third SbPh₃ ligand. A possible pathway involving rhodium(I) intermediate species was also taken into account. The calculated geometry parameters of models of complexes 1 and 2 are in good agreement with the available X-ray data. Presented relative energies of the studied reactions are in good agreement with the relative yields of 1 and 2.