949582-89-2Relevant academic research and scientific papers
Pyrrolide-supported lanthanide alkyl complexes. influence of ligands on molecular structure and catalytic activity toward isoprene polymerization
Yang, Yi,Liu, Bo,Lv, Kui,Gao, Wei,Cui, Dongmei,Chen, Xuesi,Jing, Xiabin
, p. 4575 - 4584 (2007)
The N,N-bidentate ligands 2-{(N-2,6-R)iminomethyl)}pyrrole (HL1, R = dimethylphenyl; HL2, R = diisopropylphenyl) have been prepared. HL1 reacted readily with 1 equiv of lanthanide tris(alkyl)s, Ln(CH2SiMe3)3(THF)2, affording lanthanide bis(alkyl) complexes L1Ln(CH2SiMe 3)2(THF)n (la, Ln = Lu, n = 2; lb, Ln = Sc, n -1) via alkane elimination. Reaction of the bulky ligand HL2 with 1 equiv of Ln(CH2SiMe3)3(THF)2 gave the bis(pyrrolylaldiminato) lanthanide mono(alkyl) complexes L2 2Ln(CH2SiMe3)(THF) (2a, Ln = Lu; 2b, Ln = Sc), selectively. The N,N-bidentate ligand HL3, 2- dimethylaminomethylpyrrole, reacted with Ln(CH2SiMe3) 3(THF)2, generating bimetallic bis(alkyl) complexes of central symmetry (3a, Ln = Y; 3b, Ln = Lu; 3c, Ln = Sc). Treatment of the N,N,N,N-tetmdentatc ligand H2L4, 2,2′-bis(2,2- dimethylpropyldiimino)methylpyrrole, with equimolar Lu(CH2SiMe 3)3(THF)2 afforded a C2-symmetric binuclear complex (4). Complexes 3a, 3b, 3c, and 4 represent rare examples of THF-free binuclear lanthanide bis(alkyl) complexes supported by non-cyclopentadienyl ligands. AU complexes have been tested as initiators for the polymerization of isoprene in the presence of AlEt3 and [Ph3C][B(C6F5) 4]. Complexes la, lb, and 3a show activity, and lb is the most active initiator, whereas 2a, 2b, 3b, 3c, and 4 are inert. The microstructure of the resultant polyisoprene has a cis-1,4 or trans-1,4 configuration depending on the initiator applied.
