Synthesis, Characterization of Rare‐Earth Metal Chlorides Bearing Indolyl‐Based NCN Pincer Ligand and Their Catalytic Activity toward 1,4‐cis Polymerization of Isoprene

Abstract

Main observation and conclusion 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 (κ3‐L)RECl2(THF) (RE = Sc(2), Yb(3)), and dimeric form [(κ3‐L)RECl(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 (κ2‐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.

Controlled, one-pot synthesis of recyclable poly(1,3-diene)-polyester block copolymers, catalyzed by yttrium β-diketiminate complexes

“…Previous reports have indicated that higher concentrations of IP can lead to a preference for cis -1,4, which explains the higher cis -1,4 selectivity at shorter reaction times. 28 It is interesting that the longer reaction time with 8 ( Table 1 , entry 3) has no presence of cis -1,4 selectivity, while the shorter time has 8% cis -1,4 selectivity ( Table 1 , entry 6). Since cis -1,4 selectivity seems to drop with IP concentration, this could be due to the cis -1,4 getting buried in the baseline of the NMR spectrum for the long reaction times.…”

Noninnocent Behavior of a (3-Imino)indol-2-yl Ligand in Metal Complexes

“…We had found that the (3-imino)­indole 1-(2′-(CH 2 ) 4 NCH 2 CH 2 )-3-(2′,6′-Pr i 2 C 6 H 3 NCH)­C 8 H 5 N) can be deprotonated by Bu n Li to form the ((3-imino)­indol-2-yl)lithium salt 2-Li-1-(2′-(CH 2 ) 4 NCH 2 CH 2 )-3-(2′,6′-Pr i 2 C 6 H 3 NCH)­C 8 H 5 N) . This lithium salt can perform salt elimination reactions with lanthanide halides to yield (3-imino)­indol-2-yl lanthanide complexes .…”

“…(3-Imino)­indol-2-yl anions can be viewed as derivatives of the 4-alkenyl anions of but-2-en-1-imines. In recent years, some of us (Wang and Zhou) have found that these types of anions are useful C , N -chelating ligands for the preparation of lanthanide complexes that show high catalytic activity in isoprene polymerization. − Noting that transition-metal complexes of (3-imino)­indol-2-yl ligands are scarce, , we then initiated a study on 3d metal complexes of (3-imino)­indol-2-yl ligands. Herein, we wish to report the synthesis, characterization, and redox properties of iron complexes bearing (3-imino)­indol-2-yl ligands, which revealed that this type of C , N -chelating ligand is redox noninnocent.…”

Synthesis of Bimodal Distributed Cyclic Olefin Copolymers with Improved Tensile Properties

“…[ 13 ] Since then, various catalysts including metallocene catalysts, [ 13‐18 ] half‐metallocene catalysts, cyclopentadienyl (Cp)‐free group 4 metal catalysts, late transition metal catalysts, and more recently cationic rare earth metal half‐sandwich alkyls have been reported to catalyze copolymerization of ethylene and NBE and other cyclic olefin monomers (Scheme 1). [ 19‐29 ] The resulting COCs with promising physical properties have also attracted extensive attention in both industrial and academic communities. [ 30‐43 ] Mitsui and Polyplastics have launched their commercial COCs: APEL® and TOPAS®, respectively.…”