Theoretical studies on beta-aryl elimination from Rh(I) complexes.

Beta-aryl eliminations in a series of rhodium alkoxide, alkyl and amido complexes were investigated with the aid of density function theory calculations at the Becke3LYP level. Our calculation results indicate that the typical barriers for beta-aryl eliminations are in the range of 20-25 kcal mol(-1). For comparison, beta-allyl and beta-vinyl eliminations were also studied. It was found that beta-allyl elimination is noticeably more favourable than beta-aryl elimination while beta-vinyl elimination is only slightly more favourable. The reversible reactions of beta-aryl elimination correspond to the insertion reactions into a metal-aryl bond. On the basis of the thermochemistry calculated, we discussed the factors influencing the thermodynamic preference of the beta-aryl elimination vs. insertion (the reversible process). The results indicate that the preference can be switched when different substrates and ligands are used.