Alkyl Rare Earth Complexes Supported By Amidinate Ligands: Synthesis, Structures, And Catalytic Activity For Isoprene Polymerization

Reaction of RNH2with HC(OEt)3yielded HC(=NAr)(NHAr) in58%yield1(Ar=2,6-iPr2C6H3);51%yield2(Ar=2、6-Me2C6H3).Treatment of Ln(CH2SiMe3)3(thf)x(Ln=Y, Er, Dy, X=2; Ln=Sm, X=3) with2equiv of1or2in hexane under0oC for3h. The solution wasconcentrated and recrystallization, gave novel six coordinate diamidinaterare earth alkyl complexes [HC(N-2,6-iPr2C6H3)2]2YCH2SiMe3(thf)(3)in72%yield;[HC(N-2,6-(CH3)2C6H3)2]2YCH2SiMe3(thf)(4) in71%yield;[HC(N-2,6-iPr2C6H3)2]2ErCH2SiMe3(thf)(5) in73%yield;[HC(N-2,6-iPr2C6H3)2]2DyCH2SiMe3(thf)(6) in70%yield;[HC(N-2,6-iPr2C6H3)2]2SmCH2SiMe3(thf)(7) in64%yield. One-pot saltmetathesis reaction of anhydrous NdCl3with two equivalent of amidinatelithium [HC(N-2,6-iPr2C6H3)2]Li, following the introduction of oneequivalent of LiCH2SiMe3in THF at room temperature afforded[HC(N-2,6-iPr2C6H3)2]2NdCH2SiMe3(thf)(8) in65%yield. All thecomplexes were characterized by X-ray single crystal diffraction;3,4were characterized by NMR spectroscopy.In the presence of organoaluminium and with combination of oneequivalent of [Ph3C][B(C6F5)4], complexes3to8show activity towardsisoprene polymerization to give high molecular weight polyisoprene(Mn>104) with regioselectivity depending on the sequence of additionsof aluminium and borate compounds.