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.