Pyrrolide-ligated organoyttrium complexes. Synthesis, characterization, and lactide polymerization behavior
作者：Yang, Y,Li, SH,Cui, DM,Chen, XS,Jing, XB
關(guān)鍵字：earth-metal complexes; c5me5/er-ligated samarium(ii) complexes; beta-diketiminato ligands; imine chelate ligands; ethylene polymerization; yttrium complexes; block-copolymerization; titanium complexes; styrene polymerization; olefin polymerization
論文來(lái)源：期刊
具體來(lái)源：http://pubs.acs.org/doi/abs/10.1021/om060781y
發(fā)表時(shí)間：2007年
The N,N-bidentate ligand 2-{(N-2,6-diisopropylphenyl)iminomethyl)}pyrrole (L1) and the N,N,P-tridentate ligand 2-{(N-2-diphenylphosphinophenyl)iminomethyl)}pyrrole (L2) have been prepared. Their reactions with homoleptic yttrium tris(alkyl) compound Y(CH2SiMe3)3(THF)2have been investigated. Treatment of Y(CH2SiMe3)3(THF)2 with 1 equiv of L1 generated a THF-solvated bimetallic (pyrrolylaldiminato)yttrium mono(alkyl) complex (1) of central symmetry. In this process, L1 is deprotonated by metal alkyl and its imino C
N group is reduced to C?N by intramolecular alkylation, generating dianionic species that bridge two yttrium alkyl units in a unique η5/η1:κ1 mode. The pyrrolyl ring behaves as a heterocyclopentadienyl ligand. Reaction of Y(CH2SiMe3)3(THF)2 with 2 equiv of L1 afforded the monomeric bis(pyrrolylaldiminato)yttrium mono(alkyl) complex (2), selectively. Amination of 2 with 2,6-diisopropylaniline gave the corresponding yttrium amido complex (3). In 3 the pyrrolide ligand is monoanionic and bonds to the yttrium atom in a η1:κ1 mode. The homoleptic tris(η1:κ1-pyrrolylaldiminato)yttrium complex (4) was isolated when the molar ratio of L1 to Y(CH2SiMe3)3(THF)2 increases to 3:1. Reaction of L2 with equimolar Y(CH2SiMe3)3(THF)2 afforded an asymmetric binuclear complex (5). The dianionic N,N,P tridentate moieties derived from L2 coordinate to yttrium atoms in η5/η1:κ2modes, generating tetrahedron and trigonal/pyramidal geometry around the two metal centers, respectively. Both alkylation of the imino CN group of ligand L2 and the pyrrole''s ability to act similar to a heterocyclopentadienyl moiety were also found in complex 5. Complexes 1?3 and 5 initiated polymerizations of d,l-lactide to give atactic polylactides with high molecular weights and narrow molecular weight distributions.
