Then, we performed the optimization of VL parameters. In this case, the objective function (F) was set to be the sum of the activation energy (ΔE ‡ ) and the range confining penalty function (P), and seven VL parameters (r0, a1, a2, b1, b2, c1 and c2) were optimized to minimize F. As in the previous example, the parameter set which reproduce dppe (pVL Ph ) was used as the initial parameter, and the ranges of VL parameters were set to be 1.2-2.4 Å for 𝑟 7 , 1.0-6.0 Å for a1, a2, b1, b2 and c1, and 1.0-3.514 Å for c2. The results are summarized in the bottom of Figure . The calculation converged after nine iterations, and steric parameters (a1, a2, b1, b2, c1 and c2) changed little. Instead, the electronic parameter r0 changed significantly, converging at 2.345 Å, which is close to the upper limit (2.4 Å). The activation energy (ΔE ‡ ) with the optimized parameter was calculated to be 14.9 kcal/mol, which is much lower than the calculated values for dfmpe or 1,2-bis(difluorophosphino)ethane (Figure ). This result could indicate that, if dppe-type ligands with even more electron-deficient substituents are synthesized, the desired reductive elimination can be further accelerated. Although designing such a highly electrondeficient molecule is not an easy task, this might be achieved by introducing unique design strategies for electron-withdrawing ligands, such as the use of cationic substituents 20 or replacing phosphorous atoms with arsenic 21 .