Rare-Earth Metal Alkyl Complexes And Ncn Pincer Rare-Ea-Rth Metal Dichlorides Supported By 1-(N-Piperidineethyl)-3-Imino-Functionalized Indolyl Ligands:Synthesis,Characteriz-Ation And Catalytic Activity For Isoprene Polymerization

The proligands[1-(2-C5H10NCH2CH2)-3-(2,6-iPr2C6H3N=CH)-C8H5N](HL1)and[1-(2-C5H10NCH2CH2)-3-(C10H15N=CH)-C8H5N](HL2)have been synthesized.A series of new mononuclear organo-rare-earth metal dialkyl complexes[?1:?1-1-(2-C5H10NCH2CH2)-3-(2,6-iPr2C6H3N=CH)-C8H4N]RE(CH2SiMe3)2(THF)2(RE=Yb(4a),Er(4b),Y(4c),Dy(4d))and mononuclear organo-rare-earth metal monoalkyl complexes[?1:?1-1-(2-C5H10NCH2CH2)-3-(C10H15N=CH)-C8H4N]2RE(CH2SiMe3)(THF)(RE=Yb(8a),Er(8b),Y(8c),Dy(8d),Gd(8e))supported by 1-(N-piperidineethyl)-3-imino-functionalized indolyl ligands were obtained by treatment of RE(CH2SiMe3)3(THF)2(RE=Yb,Er,Y,Dy,Gd)with 1 equiv of corresponding proligands HL1 or HL2.Then,the lithiation of the proligands HL1 or HL2 provided L1-Li and L2-Li.A series of new dinuclear NCN Pincer organo-rare-earth dichlorides{[?3-N,C,N-1-(2-C5H10NCH2CH2)-3-(2,6-iPr2C6H3N=CH)-C8H4N]RE(?2-Cl)Cl(THF)}2(RE=Y(6a),Dy(6b),Gd(6c))supported by 1-(N-piperidineethyl)-3-imino-functionalized indolyl ligands were obtained by treatment of RECl3(RE=Y,Dy,Gd)with 1 equiv of corresponding L1-Li.Due to the different addition sequence for the starting materials,coordination and steric properties of the ligands,two erbium complexes were obtained by treatment of ErCl3 with 1 equiv of corresponding L2-Li:organo-rare-earth metal complex[?1:?1-1-(2-C5H10NCH2CH2)-3-(C10H15N=CH)-C8H4N]3Er(10)and dinuclear organo-rare-earth chloride{[?1:?1-1-(2-C5H10NCH2CH2)-3-(C10H15N=CH)-C8H4N]Er(?2-Cl)Cl2Li(THF)2}2(11).All the complexes were identified by single-crystal X-ray diffraction technique and characterized by IR and elemental analysis,the yttrium complexes were additionally characterized by NMR.Moreover,the performances of the NCN Pincer organo-rare-earth metal dichlorides for the isoprene polymerization were studied.The experimental results showed that the synthesized pincer complexes have a universality on the type of the organoboron reagents([Ph3C][B(C6F5)4]?B(C6F5)3?[PhMe2NH][B(C6F5)4])and alkylaluminum reagents(AlMe3?AlEt3?AliBu3).Study of the catalytic performance of these complexes revealed that the complexes can display high activity and high 1,4-cis-selectivity for the isoprene polymerization in the presence of organoboron reagents and alkylaluminum reagents.At room temperature,the three-component homogeneous catalytic system of which the complex 6c can catalyze complete polymerization of 8000-10000 equivalents of isoprene monomer in a short period of time,and at 0?,the polymerization of 500 equivalents of isoprene monomer had a 1,4-cis-selectivity of 100%and a molecular weight of more than one million.