Rare-earth metal dialkyl complexes [1-Bn-3-(DippN=CH)C₈H₄N]RE(CH₂SiMe₃)₂(thf)₂ (Dipp = 2,6-ⁱPr₂C₆H₃, RE = Y (1) and Er (2)) were prepared through the cyclometalation reactions of the N-Bn-3- imino-functionalized indolyl ligand 1-Bn-3-(DippN=CH)C₈H₅N with one equivalent of rare-earth metal trialkyl precursors. The structures of compounds 1 and 2 were confirmed by X-ray crystal analyses and characterized by elemental analysis, IR, NMR spectroscopy wherein applicable. In the presence of cocatalysts, these rare-earth metal dialkyl complexes initiated isoprene polymerization with a high activity (95% conversion of 2000 equivalent of isoprene in 360 min), producing polymers with high regioselectivity (1,4-polymers up to 91%).