Versatile Ln2(渭-NR)2-Imide Platforms for Ligand Exchange and Isoprene Polymerization
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- 作者：Dorothea Sch盲dle ; Christoph Sch盲dle ; David Schneider ; C盲cilia Maichle-M枚ssmer ; Reiner Anwander
- 刊名：Organometallics
- 出版年：2015
- 出版时间：October 26, 2015
- 年：2015
- 卷：34
- 期：20
- 页码：4994-5008
- 全文大小：766K
- ISSN：1520-6041
文摘
Bimetallic rare-earth-metal imide complexes Ln2(渭2-Ndipp)(渭3-Ndipp)[(渭2-Me)2AlMe](AlMe4)2 (3-Ln; Ln = Y, La, Ce, Nd; dipp = 2,6-diisopropylphenyl) have been obtained from the reaction of Ln(AlMe4)3 (1-Ln) with Li(NHdipp) (2). X-ray diffraction studies of toluene-soluble 3-Ln revealed an unusual Ln[{(渭2-Me)2AlMe}(渭3-Ndipp)]Ln moiety as the most striking feature. Facile salt-metathetical exchange of the tetramethylaluminato ligands in 3-Ln with K(L) (L = N(SiMe3)2, Cp鈥? allowed for the isolation of Ln2(Ndipp)2[N(SiMe3)2]2(AlMe3) (4-La), partially exchanged Ln2(Ndipp)2(Cp鈥?(AlMe4)(AlMe3) (5-La, Cp鈥?= C5Me4SiMe3), and Ln2(Ndipp)2(Cp鈥?2(AlMe3) (6-La). Attempted cleavage of the AlMe3 moiety in 3-Ln with THF led to C鈥揌 bond activation of one of the isopropyl methine moieties to produce Ln2(渭2-Ndipp)[(渭3-NC6H3-2-CMe2-6-iPr)Al(渭2-Me)2](AlMe4)2 (7-La). Selective cleavage of the bridging AlMe3 鈥渃ap鈥?was achieved by addition of DMAP (DMAP = 4-dimethylaminopyridine) to produce [Ln(渭2-Ndipp)(AlMe4)(DMAP)]n (8-Ln; Ln = La, Ce) and concomitantly DMAP路AlMe3. The organoaluminum-free compounds [Ln(渭2-Ndipp){N(SiMe3)2}(DMAP)]2 (9-Ln; Ln = La, Ce), [Ln(渭2-Ndipp)(Cp鈥?(DMAP)]2 (10-La), and [Ln(渭2-Ndipp)(OAr)(DMAP)]2 (11-Ln; Ln = La, Ce; Ar = 2,6-di-tert-butyl-4-methylphenyl) were obtained via reactions of 8-Ln with K(L) (L = Cp鈥? N(SiMe3)2, OAr). In the presence of activators [Ph3C][B(C6F5)4] and [PhNMe2H][B(C6F5)4], AlEt2Cl complexes 3-Ln, 5-Ln, and 7-Ln initiate the polymerization of isoprene to yield PIPs with narrow molecular weight distributions, involving new imido-supported bimetallic catalysts.