Dialkyl Rare Earth Complexes Supported by Potentially Tridentate Amidinate Ligands: Synthesis, Structures, and Catalytic Activity in Isoprene Polymerization

被引:32
作者
Rad'kov, Vassily Yu [1 ]
Skvortsov, Grigorii G. [1 ]
Lyubov, Dmitry M. [1 ]
Cherkasov, Anton V. [1 ]
Fukin, Georgy K. [1 ]
Shavyrin, Andrei S. [1 ]
Cui, Dongmei [2 ]
Trifonov, Alexander A. [1 ]
机构
[1] Russian Acad Sci, GA Razuvaev Inst Organometall Chem, Nizhnii Novgorod 603950, Russia
[2] Chinese Acad Sci, State Key Lab Polymer Phys & Chem, Changchun Inst Appl Chem, Changchun 130022, Peoples R China
基金
俄罗斯基础研究基金会;
关键词
Lanthanides; Ligand design; Polymerization; YTTRIUM ALKYL COMPLEXES; COORDINATION CHEMISTRY; ORGANOYTTRIUM CHEMISTRY; MOLECULAR-STRUCTURE; METAL-CATALYSTS; CYCLOPENTADIENYL; REACTIVITY; GROUP-3; SCANDIUM; ACTIVATION;
D O I
10.1002/ejic.201101440
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
Two new amidines that contain a pendant Lewis base in the side arm, 2-MeOC6H4NC(tBu)NH(2,6-R2C6H3) (R = Me, iPr), were synthesized and successfully employed as tridentate ligands for the preparation of the dialkyl rare earth complexes [2-MeOC6H4NC(tBu)N(2,6-R2C6H3)]Ln(CH2SiMe3)2(L)n {Ln = Y, Lu; R = Me, iPr; L = thf (n = 2), dme (n = 1)}. These ligands provided enhanced stability for the complexes. The X-ray structure determinations revealed that intramolecular coordination of the 2-MeOC6H4 group is realized if a thf molecule is coordinated to the metal center (Ln = Y, Lu), which results in the coordination number of six. The treatment of complex [2-MeOC6H4NC(tBu)N(2,6-Me2C6H3)]Lu(CH2SiMe3)2(thf) with dme afforded a six-coordinate dme adduct in which the methoxy group of the amidinate ligand has drifted out from the metal coordination sphere. The reaction of [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(CH2SiMe3)2(thf) with 2,6-diisopropylaniline in hexane at 70 degrees C, regardless of the ratio of the reagent, afforded the six-coordinate diamido compound [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(NHC6H3-2,6-iPr2)2(thf), for which intramolecular coordination of the oxygen atom of the side chain was detected by an X-ray study. Complex [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(CH2SiMe3)2(thf) was evaluated as a precatalyst for isoprene polymerization. The ternary system [2-MeOC6H4NC(tBu)N(2,6-iPr2C6H3)]Y(CH2SiMe3)2(thf)/[Ph3C][B(C6F5)4]/AliBu3provided isoprene polymerization with moderate activity but without control of the regioselectivity (3,4-regularity was slightly predominant at 52?%). Nevertheless, high 1,4-trans-selectivity was found (96%) for the 1,4-polyisoprenes. The obtained polyisoprene has a Mn of 13.0 x 10(4) and moderate polydispersity (2.12).
引用
收藏
页码:2289 / 2297
页数:9
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