Scandium Half-Metallocene-Catalyzed Syndiospecific Styrene Polymerization and Styrene−Ethylene Copolymerization:  Unprecedented Incorporation of Syndiotactic Styrene−Styrene Sequences in Styrene−Ethylene Copolymers

Abstract

On treatment with 1 equiv of [Ph3C][B(C6F5)4], the scandium half-sandwich bis(alkyl) complex (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) showed extremely high activity (up to 1.36 x 104 kg of sPS/(mol Sc.h)) and syndiospecificity (rrrr > 99%) for the polymerization of styrene at room temperature in toluene. More remarkably, this catalyst system could also effect the syndiospecific copolymerization of styrene with ethylene to yield styrene-ethylene copolymers having syndiotactic styrene-styrene sequences. The styrene content in the copolymers could be easily controlled by changing the styrene feed and could reach higher than 80 mol %. This is the first example of formation of such types of styrene-ethylene copolymers, which are expected to show novel properties.

Synthesis of ethylene–styrene copolymer containing syndiotactic polystyrene sequence by trivalent titanium catalyst

“…Assignments of the resonances of the copolymer were carried out according to the previous reports. 8,18,[20][21][22][23][24][25] The spectrum of the insoluble part, obtained by TCE extraction of the crude product in Run 11, is shown in Figure 3. In addition to continuous homogeneous monomer sequences consisting of ethylene-ethylene (30.1 p.p.m.)…”

“…[9][10][11][12][13][14][15][16][17] However, there have been only limited reports on the synthesis of copolymers containing long syndiotactic styrene-styrene sequences. Hou and co-workers 18 have reported that rare-earth metal-based catalyst systems promote not only the syndiotactic homopolymerization of styrene, but also copolymerization with ethylene, in which the Cp¢Sc(CH 2 SiTMS) 2 /Ph 3 CÁB(C 6 F 5 ) 4 [Cp¢¼C 5 Me 4 (CH 2 TMS)] catalyst system produces a multi-block copolymer consisting of a crystalline SPS part and an ethylene-rich part. Carpentier and co-workers 19 have also reported an ansa-lanthanidocene catalyst that can synthesize a copolymer containing long syndiotactic styrene-styrene sequences separated by a single or a few ethylene units.…”

Sixty Years of the Chemistry of Rare-earth Organometallic Complexes

“…图 13 烷烃消除反应合成单茂钇双烷基配合物 Figure 13 Synthesis of mono-Cp yttrium dialkyl complexes via alkane elimination [133] , 从而 开启了单茂稀土阳离子配合物体系催化高分子合成的 篇章. 随后的研究发现单茂稀土阳离子配合物体系还可 以高活性地催化乙烯、1-己烯、苯乙烯、丁二烯和异戊 二烯等均聚, 以及催化乙烯与 1-己烯、丁二烯、异戊二 烯、 降冰片烯等的共聚(图 14) [134] .…”

Half-Sandwich Rare Earth Metal Complexes as Novel Catalysts for Olefin Polymerization and Other Chemical Transformations

“…2c, 4,5 The bis(trimethylsilylmethyl) rare earth complexes bearing other cyclopentadienyl groups such as C 5 H 5 (1a), 6 C 5 MeH 4 (1b), 6 C 5 Me 4 H (1c), 6 1,3-(Me 3 Si) 2 C 5 H 3 (1d), 7 C 5 Me 5 (1eLn), 6 and C 5 Me 4 CH 2 CH 2 PPh 2 (1g-Ln) 8 have also been prepared similarly (Scheme 1). The analogous complexes bearing the cyclopentadienyl ligands with a phosphine or ether side arm such as C 5 Me 4 CH 2 CH 2 PPh 2 (1g) 6 and C 5 Me 4 C 6 H 4 OMe-o (1h) 6 are obtained by the one-pot metathetical reactions of [ScCl 3 (thf) 3 ] with 1 equivalent of the potassium salts of the ligands and 2 equivalents of LiCH 2 SiMe 3 (Scheme 2).…”

“…The half-sandwich mono-and dialkyl rare earth metal complexes are prepared either by alkane elimination reactions between trialkyl rare earth complexes and the neutral cyclopentadiene derivatives or by metathetical reactions of rare earth trichlorides with the alkali metal salts of the corresponding ligands. 4 ] generates easily the corresponding cationic monoalkyl species, which serve as excellent catalysts for the polymerization and copolymerization of a variety of olefins to yield a new family of polymer materials that show novel properties but are difficult to prepare by other catalysts. The half-sandwich monoalkyl rare earth complexes bearing the silylene-linked cyclopentadienylarylamido ligands act as excellent catalysts for the catalytic dimerization of terminal alkynes, cross coupling of terminal alkynes with isocyanides, and the catalytic addition of terminal alkyne CH, amine NH, and phosphine PH bonds to carbodiimides.…”