Structure-reactivity relationships in rare-earth metal carboxylate-based binary ziegler-type catalysts

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(O2CC6H2iPr3-2,4,6)3}n (Ln = Y, La, Nd, Gd, Lu), {Ln(O2CC6H2tBu3-2,4,6)3(THF)}n (Ln = Y, La), {Ln(O2CC6H3Ph2-2,6)3(THF)}n (Ln = Y, La), and {Ln(O2CC6H3Mes2-2,6)3(THF)}n (Ln = Y, La) were obtained quantitatively according to the silylamide route from Ln[N(SiMe3)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(O2CC6H2Me3-2,4,6)2(μ-O2CC6H2Me3-2,4,6)(DMSO)2]2 depending on the metal i...