Heterogenized “Ligand-Free” Lanthanide Catalysts for the Homo- and Copolymerization of Ethylene and 1,3-Butadiene

Abstract

Silica-supported lanthanide catalysts have been prepared from the reaction of dehydroxylated silica and tris(bistrimethylsilyl)amido lanthanides Ln[N(SiMe 3)2]3 (Ln ) Sc, Y, La, Nd, Sm, Gd, Dy). On activation with Al i Bu3 (TIBA), the compounds catalyze the polymerization of ethylene, with the scandium catalyst showing the highest activity. There is an inverse relationship between ionic radius of the lanthanide metal and the activity of the resulting catalyst. The polymer produced was highly linear and of high molecular weight. Activation with magnesium alkyls was less effective but gave polyethylene of slightly higher molecular weight. The supported lanthanides, when activated with TIBA, were also active for the polymerization of 1,3-butadiene, with very high molecular weight polymers being produced. In all cases the polymer was found to be predominately 1,4-cis (typically 85-90% by diad analysis), with only scandium producing a much higher level of 1,4-trans units. The system was also shown to copolymerize ethylene and butadiene, with large differences in the polymeric products depending on the both the choice of the lanthanide and the feed ratio of the monomer. With both neodymium and dysprosium multiblock polymers consisting of 1,4-cis, 1,4-trans, and ethylene blocks were obtained. With scandium two distinct modes of polymerization were detected, with both multiblock 1,4-cis and a somewhat alternating ethylene/1,4-trans block structure observed in the 13 C NMR spectra.

β-SiH-Containing Tris(silazido) Rare-Earth Complexes as Homogeneous and Grafted Single-Site Catalyst Precursors for Hydroamination

“…67 The correlations involving Si−H(H3) are suppressed in Figure 5A because the 1 H{ 13 C} idHETCOR scheme uses two CP transfers ( 1 H → 13 C and 13 C → 1 H); however, these protons are quantitatively observed in the 1 H MAS SSNMR spectra of 2@MSNs ( Figure S27). Note that the carbon intensity in dimethylsilyl groups (C1) relative to C2 decreases in the MSN 700 sample ( Figure S28), suggesting that C1 also includes surface-bound −SiHMe 2 groups whose population is reduced on MSNs pretreated at higher temperature (see also the discussion of 29 Si spectra below). Importantly, we do not detect any THF ligands in the 2@MSN 550 sample, which would yield 13 C resonances at 26 and 68 ppm.…”

One‐Pot Synthesis of Lactide–Styrene Diblock Copolymers via Catalytic Immortal Ring‐Opening Polymerization of Lactide and Nitroxide‐Mediated Polymerization of Styrene

“…The simple homoleptic amido complexes Y[N(SiMe 3 ) 2 ] 3 1, [32] Zn[N(SiMe 3 ) 2 ] 2 2, [33] Mg[N-(SiMe 3 ) 2 ] 2 3, [34] Ca[N(SiMe 3 ) 2 ] 2 (thf) 2 4 [35] were selected for an initial screening of initiators and were synthesized according to www.chemsuschem.org published procedures. This arbitrary selection was made on account of three factors: 1) all four complexes are easily synthesized on a multigram scale from relatively inexpensive precursors; 2) they are either liquid (2) or highly soluble in all common organic solvents (ethers, aliphatic, and aromatic hydrocarbons), and therefore their solubility in styrene should not be an issue; 3) they are based on environmentally benign metals.…”

“…1-Hydroxy-2-phenyl-2-(2',2',6',6'-tetramethyl-1'-piperidinyloxy)ethane (AA-OH), [24a] Y[N(SiMe 3 ) 2 ] 3 1, [32] Zn[N(SiMe 3 ) 2 ] 2 2, [33] {Mg[N(SiMe 3 ) 2 ] 2 } 2 3, [34] Ca[N(SiMe 3 ) 2 ] 2 (thf) 2 4, [35] and [BDI-iPr]Zn-N(SiMe 3 ) 2 5 [5] were prepared as described in the literature. Isopropanol employed for polymerization purposes (HPLC grade, VWR) was dried and distilled over magnesium turnings and then stored over activated 3 molecular sieves.…”

Synthesis of Highcis-1,4-BR with Neodymium for the Manufacture of Tires

“…The Mooney viscosity shows good correlation with the molecular weight when the high cis-1,4-BR has the same macrostructure regarding the linearity of the macromolecule. As branches, the hydrodynamic volume of the chains decreases, causing a decrease in the Mooney viscosity but not in molecular weight, so it is considered feasible to establish a relationship between the molecular weight and Mooney viscosity to be formed [19,20]. The Mooney viscosity behavior versus Mw is shown in Figure 6, where it is evident that with increasing TIBA from 100 mM to 200 mM it is possible to obtain products with Mooney viscosity of 25 MU and Mw × 10 3 = 350 ± 150 g/mol.…”