197774-00-8Relevant articles and documents
Structure - Reactivity relationships in rare-earth metal carboxylate-based binary Ziegler-type catalysts
Fischbach, Andreas,Perdih, Franc,Herdtweck, Eberhardt,Anwander, Reiner
, p. 1626 - 1642 (2008/10/09)
The organoaluminum-mediated alkylation of tailor-made rare-earth metal carboxylate complexes was studied, and implications of the degree of Ln alkylation and organoaluminum-chloride-mediated cation formation for 1,3-diene polymerization were investigated. Highly substituted rare-earth metal benzoate complexes {Ln(O2CC6H2Me3-2,4,6) 3}n (Ln = Y, La, Nd), {Ln(O2CC 6H2iPr3-2,4,6)3}n (Ln = Y, La, Nd, Gd, Lu), {Ln(O2CC6H2tBu 3-2,4,6)3(THF)}n (Ln = Y, La), {Ln(O 2CC6H3Ph2-2,6)3(THF)}n (Ln = Y, La), and {Ln(O2CC6H3Mes 2-2,6)3(THF)}n (Ln = Y, La) were obtained quantitatively according to the silylamide route from Ln[N(SiMe 3)2]3 and alkyl(aryl)-substituted benzoic acids. Such oligomeric carboxylate complexes are insoluble in aliphatic and aromatic solvents, but could be crystallized from donor solvents such as THF, DMSO, and pyridine. X-ray crystallographic analyses indicated the formation of monomeric [Nd(O2CC6H2Me3-2,4,6) 3(DMSO)3] and dimeric [La(O2CC 6H2Me3-2,4,6)2(μ-O 2CC6H2Me3-2,4,6)-(DMSO) 2]2 depending on the metal ion size. Depending on the steric demand of the benzoate ligands, mono- and bis(tetraalkylaluminate) complexes [Me2Al(O2CC6H2/Pr 3-2,4,6)2]2Ln[(M-Me)2AlMe 2] and {Ln(O2CC6H2tBu 3-2,4,6)[(M-Me)2AlMe2]2} 2, respectively, could be identified as major product components from the reaction with excess AlR3 (R = Me, Et), by means of 1H NMR spectroscopy and X-ray structure analysis. When activated with Et2AlCl, the resulting binary Ziegler-type catalysts efficiently polymerized isoprene (>99% cis-1,4), the polymerization performance depending on the metal center (Nd > Gd > La) and the degree of alkylation ( Ln(AlMe4)2 > Ln(AlMe 4) )- Equimolar reaction of [Me2Al(O 2-CC6H2iPr3-2,4,6)2] 2Ln[(w-Me)2AlMe2] with R2AlCl (R = Me,. Et) quantitatively produced [Me2Al(O2-CC 6H2iPr3-2,4,6)]2, proposing Me2LnCl as the polymerization-initiating species. Homoleptic Ln(AlMe4)3 was spotted as a crucial reaction intermediate and was used for the high-yield synthesis of the various alkylated carboxylate complexes according to a novel tetraalkylaluminate route.
