Synthesis and Reactivity of Rare-Earth-Metal Monoalkyl Complexes Supported by Bidentate Indolyl Ligands and Their High Performance in Isoprene 1,4-cis Polymerization

A series of novel rare-earth-metal monoalkyl complexes incorporating partially rotation restricted [N,N]-bidentate indolyl ligands were synthesized and characterized, and their reactivities and catalytic activities were investigated. Treatment of [RE(CH2SiMe3)3(thf)2] with 1 equiv of 2-[(N-2,6-diisopropylphenyl)iminomethyl)]indole (2-(2,6-iPr2C6H3N═CH)C8H5NH) in toluene at room temperature afforded the rare-earth-metal monoalkyl complexes [η1:η1-2-(2,6-iPr2C6H3N═CH)Ind]2RE(CH2SiMe3)(thf) (Ind = indolyl; RE = Yb (1), Er (2), Y (3), Dy (4), Gd (5)) and the samarium complex [η1:η1-2-(2,6-iPr2C6H3N═CH)Ind]3Sm (6) via alkane elimination in good yields. Treatment of complex 2 or 3 with 1 equiv of PhSiH3 in toluene at 80 °C for 12 h afforded the dinuclear complexes {[μ-η6:η1:η1-2-(2,6-iPr2C6H3NCH2)Ind]RE[2-(2,6-iPr2C6H3N═CH)Ind]}2 (Ind = indolyl, RE = Er (7), Y (8)) in good isolated yields. Treatment of complex 2 or 3 with 1 equiv of amidine (2,6-iPr2C6H3)N═CHNH(2,6-iPr2C6H3) in toluene produced the correspondin...