Overall, the VLAO method implied that the α selectivity can be largely improved by the use of thinner and shorter substituents with stronger electron-donating ability comparing to Ph group. With the suggestion by the VLAO in hand, we then aimed at finding α-selective ligands (Figure ). Considering the requirement for electron-donating ligands, we prepared six phosphine ligands including PMe3, PEt3, PCy3, PCp3 (Cp = cyclopentyl), L1 and L2. Whereas trialkylphosphine ligands (PMe3, PEt3, PCy3 and PCp3) were chosen because they are well known to exhibit strong electron-donating nature, L1 and L2 were designed so that they have stronger electron-donating ability than PPh3 while keeping the steric effect unchanged as much as possible. The α selectivities for each ligand were then predicted. It should be noted that, whereas some of real ligands (e.g., PCy3 and PCp3) are very flexible, the VL parameters for a given ligand were determined based on a single conformer of R3PNi(CO)3 (see SI for detail). Hence, the VL only reproduces a snapshot of a ligand and cannot describe conformational flexibility (except for rotation of P-R bonds). In this study, to avoid this inherent limitation of the VL method, the prediction of the α selectivity for a given ligand was performed as follows. First, upon a systematical conformation search by the SC-AFIR method , the most stable conformer of R3PNi(CO)3 were determined. Then, all conformers with relative energies lower than 1.0 kcal/mol were chosen, and VL parameters for each of these conformers were determined (see Table ). After that, the calculations of α-TS and β-TS using each set of VL parameters were performed, and the α selectivity of the ligand was estimated as the average value of those for each conformer weighted by the Boltzmann distribution of R3PNi(CO)3. As a result, the α selectivities were estimated to be 88.4% for PMe3, 36.5% for PEt3, 4.2% for PCy3, 29.5% for PCp3, 54.1% for L1 and 98.7% for L2, respectively. As expected, both L1 and L2 were predicted to exhibit higher α selectivity than PPh3 (40.7%). On the contrary, the α selectivities of PEt3, PCy3 and PCp3 were predicted to be lower than PPh3 despite their high electron-donating ability. This is because these alkyl groups are much thicker than the phenyl group, making corresponding ligands sterically unfavorable. It is important to noted that the α selectivity of PCp3 (29.5%) differs significantly from the value estimated from only the most stable conformer (98.5%). This result highlights the importance of the contributions from not only the most stable but also thermally accessible conformers of a ligand.