925213-12-3Relevant academic research and scientific papers
Pyrrolide-ligated organoyttrium complexes. Synthesis, characterization, and lactide polymerization behavior
Yang, Yi,Li, Shihui,Cui, Dongmei,Chen, Xuesi,Jing, Xiabin
, p. 671 - 678 (2008/10/09)
The N,N-bidentate ligand 2-{(N-2,6-diisopropylphenyl)iminomethyl)}pyrrole (L1) and the N,N,P-tridentate ligand 2-{(N-2-diphenylphosphinopnenyl) iminomethyl)}pyrrole (L2) have been prepared. Their reactions with homoleptic yttrium tris(alkyl) compound Y(CH2SiMe3) 3(THF)2 have been investigated. Treatment of Y(CH 2SiMe3)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(η1κ 1-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:κ2 modes, generating tetrahedron and trigonal/pyramidal geometry around the two metal centers, respectively. Both alkylation of the imino C-N 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.
