Highly Efficient Dimerization of Ethylene by (Imido)vanadium Complexes Containing (2-Anilidomethyl)pyridine Ligands: Notable Ligand Effect toward Activity and Selectivity

(Imido)vanadium(V) complexes containing the (2-anilidomethyl)pyridine ligand, V(NR)Cl2[2-ArNCH2(C5H4N)] (R = 1-adamantyl (Ad), cyclohexyl (Cy), phenyl), exhibit remarkably high catalytic activities (e.g. TOF = 2 730 000 h−1 (758 s−1) by V(NAd)Cl2[2-(2,6-Me2C6H3)NCH2(C5H4N)) for ethylene dimerization in the presence of MAO, affording 1-butene exclusively (selectivity 90.4 to >99%). The steric bulk of the imido ligand plays an important role in the selectivity (polymerization vs dimerization), and the electronic nature directly affects the catalytic activity (activity: R = Ad > Cy > Ph).