A novel indolyl-based NCN pincer ligand precursor HL (HL =(1-(2-(CH2)4NCH2CH2)-3-(2,6-ipr2C6H3N=CH)C8H5N)) was rationally and precisely designed,and successfully prepared in a high yield.Lithiation of HL with nBuLi in n-hexane,followed by treatment with RECl3 in THF led to the isolation of rare-earth metal chlorides in monomeric form (K3-L)RECI2(THF) (RE =Sc(2),Yb(3)),and dimeric form[(κ3-L)RECI(THF)(μ-Cl)]2 (RE =Er(4),Y(5)) bearing the novel indolyl-based NCN pincer ligand in designed pincer ligation depending on different metal ionic radii;and the chloride bridged rare-earth metal and lithium mixed complexes in form (K2-L)2RE(μ-Cl)2Li(THF)2 (RE=Y(6),Dy(7).All complexes were fully characterized and their structures were determined.The diamagnetic complexes 2,5 and 6 were furtherly characterized by the NMR spectroscopic method.The catalytic activity studies revealed that the central metal ions,borates,aluminum alkyls,and ligation of the central metal ions have influences on catalytic activity,and regio-and stereoselectivity for the polymerization of isoprene.With cooperation of the cocatalysts,the pincer-type yttrium chloride 5 initiated the isoprene polymerization with a high activity producing polymers with high regio-and stereoselectivity (1,4-cis polymers up to 99.6％),and the Mn as high as 8.76 × 105.