Lanthanide(II) amide complexes: Efficient initiators for the living polymerization of methyl methacrylate

Abstract

Lanthanide(II) complexes supported by amido ligands, [(C 6 H 5 [Ln ¼ Sm (3) or Yb (4); THF ¼ tetrahydrofuran], were found to initiate the polymerization of methyl methacrylate (MMA) as efficient single-component initiators (in toluene for 3 and 4 and in toluene with a small amount of THF for 1 and 2) to produce syndiotactic polymers. The catalytic behavior was highly dependent on both the amido ligand and the polymerization temperature. Initiators 3 and 4 initiated MMA polymerization over a wide range of temperatures (20 C to À40 C), whereas the polymerization with 1 and 2 proceeded smoothly only at low temperatures ( 0 C). The kinetic behavior and some features of the polymerizations of MMA initiated by 3 and 4 were studied at À40 C. The polymerization rate was first-order with the monomer concentration. The molar masses of the polymers increased linearly with the increase in the polymer yields, whereas the molar mass distributions remained narrow and unchanged throughout the polymerization; this indicated that these systems had living character. A polymerization mechanism initiated by bimetallic bisenolate formed in situ was proposed.

Bis(amido) rare-earth complexes coordinated by tridentate amidinate ligand: synthesis, structure and catalytic activity in the polymerization of isoprene and rac-lactide

“…1 They have been exhaustively explored as precursors for the preparation of electronic and ceramic materials, 2 as well as catalysts for the synthesis of various valuable chemical products. 3 Moreover they turned out to be efficient initiators for the polymerization of a large range of monomers such as ethylene, 4 styrene, 5 methyl methacrylate 6 or cyclic esters. 7 Formerly, in the pioneering work of Marks it was reported that the strength of the Ln-N bond is comparable to that of the Ln-C bond.…”

Bis(phosphinimino)methanide borohydride complexes of the rare-earth elements as initiators for the polymerization of methyl methacrylate: combined experimental and computational investigations

“…3,[9][10][11][12][13] Other organolanthanide precursors were reported to similarly favor the syndiotactic enrichment of PMMA, however, not to such a large extent. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] On the other hand, isotactic-enriched PMMA prepared from related group 3 metals are much less common. [31][32][33][34] Regarding rare earth borohydride derivatives, mono-, bis-or tris-borohydridodiamide-diamine, guanidinate, amino-or alkylsubstituted cyclopentadienyl, and alkoxide complexes have been recently reported to polymerize MMA.…”